Answers from Dr. Cordain

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With readily available modern foods, The Paleo Diet mimics the types of foods every single person on the planet ate prior to the Agricultural Revolution (a mere 500 generations ago). These foods (fresh fruits, vegetables, lean meats, and seafood) are high in the beneficial nutrients (soluble fiber, antioxidant vitamins, phytochemicals, omega-3 and monounsaturated fats, and low-glycemic carbohydrates) that promote good health and are low in the foods and nutrients (refined sugars and grains, saturated and trans fats, salt, high-glycemic carbohydrates, and processed foods) that frequently may cause weight gain, cardiovascular disease, diabetes, and numerous other health problems. The Paleo Diet encourages dieters to replace dairy and grain products with fresh fruits and vegetables -- foods that are more nutritious than whole grains or dairy products.

The Paleo Diet is the unique diet to which our species is genetically adapted. This program of eating was not designed by diet doctors, faddists, or nutritionists, but rather by Mother Nature's wisdom acting through evolution and natural selection. The Paleo Diet is based upon extensive scientific research examining the types and quantities of foods our hunter-gatherer ancestors ate. This nutritional plan is totally unlike those irresponsible, low-carbohydrate, high-fat, fad diets that allow unlimited consumption of artery-clogging cheeses, bacon, butter, and fatty meats. Rather, the foundation of The Paleo Diet is lean meat, seafood, and unlimited consumption of fresh fruits and veggies.

It is certainly true that hunter-gatherers studied during modern times did not have as great an average lifespan as those values found in fully westernized, industrial nations. However, most deaths in hunter-gatherer societies were related to the accidents and trauma of a life spent living outdoors without modern medical care, as opposed to the chronic degenerative diseases that afflict modern societies. In most hunter-gatherer populations today, approximately 10-20% of the population is 60 years of age or older. These elderly people have been shown to be generally free of the signs and symptoms of chronic disease (obesity, high blood pressure, high cholesterol levels) that universally afflict the elderly in western societies. When these people adopt western diets, their health declines and they begin to exhibit signs and symptoms of "diseases of civilization."

There are more than six billion people alive on the planet in the 21st century. Cereal grains provide more than half of the energy required to feed the world's people. Without cereal grains, there would be massive starvation of unprecedented proportion on the planet. We have walked down a path of absolute dependence upon cereal grains -- a path that cannot be reversed. However, in most western countries, cereals are not a necessity, particularly in many segments of the population that suffer most from Syndrome X and other chronic diseases of civilization. In this population, a return to a Stone Age Diet is not only possible, but highly practical in terms of long-term healthcare costs.

Conventional wisdom tells us that to lose weight we must burn more calories than we take in and that the best way to accomplish this is to eat a plant-dominated, low-fat, high-carbohydrate diet. The first part of this equation is still true -- a net caloric deficit must occur in order for weight to be lost. However, the experience for most people on low-calorie, high-carbohydrate diets is unpleasant. They are hungry all the time, and for the vast majority, any weight lost is regained rapidly or within a few months of the initial loss. The diet doctors with their low-carbohydrate, high-fat diets offer us an alternative, but this nutritional gambit is nothing more than a short term ploy to lose weight that in the long run is unhealthy because of its reliance upon fats (bacon, butter, fatty meats, cheeses, etc.) at the expense of healthful fruits and vegetables.

There is an alternative -- a diet that emulates what our hunter-gatherer ancestors ate -- a high-protein, high-fruit and veggie diet with moderate amounts of fat, but with high quantities of healthful omega-3 and monounsaturated fats. Protein has two to three times the thermic effect of either fat or carbohydrate, meaning that it revs up your metabolism, speeding weight loss. Additionally, protein has a much greater satiety value than either fat or carbohydrate, so it puts the brakes on your appetite. Finally, three recent clinical trials have shown high-protein diets to be more effective than low-fat, high-carbohydrate diets in promoting weight loss.

Most of the shrimp we eat come from Asia and South America where the shrimp are farmed. I was just wondering if the levels of omega-3 in these farmed-raised shrimp are comparable to shrimp harvested from the ocean?

To date, virtually all studies of farmed vs. wild show a slight reduction in the ratio (which is different than amounts per serving) of omega-3 fatty acids to other fatty acids within a species. Having said that, there is no doubt that farmed shrimp and other farmed fisheries products contain generous amounts of omega-3 fatty acids. For example, because farmed Atlantic salmon and rainbow trout contain a higher percentage of fatty acids than their wild counterparts, the farmed varieties actually contain more grams of omega-3 fatty acids per serving!  There is also no doubt that lean farmed shrimp and fish are far better for you than fatty feedlot beef.

Today steps are being taken by shrimp feed and fish feed manufacturers to rectify any disparity between omega-3 levels in farm-raised and wild fish and shellfish. Recent research has shown that late-stage feeding with feeds containing high concentrations of omega-3 allows the receiving muscle tissues to quickly "catch up."  The result is a farmed product that, overall, requires less omega-3 in its diet over its lifetime, and an omega-3 concentration in the tissue at harvest that is on par with or higher than wild product. This strategy will (1) help to minimize the amount of expensive fish meals and fish oils used by the aquaculture industry, (2) will still provide us with abundant amounts of omega-3 fatty acids in our diet, and (3) spare valuable wild populations of fish and shellfish from unnecessary and destructive over-harvest. The aquaculture industry understands and appreciates this issue, and is taking steps now to correct real and perceived disparities.

Click here for omega-3 fatty acids values for fish and seafood.

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The carbohydrates (unlimited fruits and veggies) in The Paleo Diet are of a low-glycemic index, meaning that they cause slow and limited rises in your blood sugar and insulin levels. Excessive insulin and blood sugar levels are known to promote a cluster of diseases called Syndrome X (obesity, hypertension, undesirable blood cholesterol and other blood lipid levels, Type 2 diabetes and gout). The high fiber, protein, and omega-3 fat content of The Paleo Diet will also help to prevent Syndrome X diseases.

Because of the unlimited amounts of fruits and veggies permitted on The Paleo Diet, your body will be slightly alkaline -- meaning that diseases and disease symptoms of acid/base imbalance (osteoporosis, kidney stones, hypertension, stroke, asthma, insomnia, motion sickness, inner ear ringing, and exercise-induced asthma) will improve.

The high soluble-fiber content of The Paleo Diet will improve most diseases of the gastrointestinal tract, and the high omega-3 fat content will improve most of the "itis" or inflammatory diseases.

When switching to The Paleo Diet after being on an ultra-low-carb diet, is it possible to gain temporary weight from eating the "unlimited" fruit allowed on your plan?

Let me take a roundabout way of answering this question first by explaining why almost all of the weight we gain comes from either dietary fat or dietary carbohydrate.

As I pointed out in Chapter 4 of The Paleo Diet, it is physiologically impossible to gain weight when lean protein is the only food consumed because of the body's limited ability to break down protein and excrete the by-product of protein metabolism (urea). This limit is called the physiological protein ceiling and varies between 30-40% of the normal caloric intake in most people, assuming they are consuming their usual (eucaloric) energy intake. Continued consumption of lean protein at or above the physiological protein ceiling without added fat or carbohydrate will elicit symptoms of so-called "rabbit starvation," a malady eliciting lethargy, diarrhea, weight loss, electrolyte imbalances, and eventual death. Hence, all people will lose body weight if limited to consumption of lean protein.

Lean protein has been shown repeatedly to be the most satiating of all three macronutrients (protein, fat, and carbohydrate). Numerous clinical trials have shown that people eat fewer calories during a high-protein meal compared to high-fat or carbohydrate meals, and they eat fewer calories at the meal immediately following a high-protein meal. Finally, lean protein has two to three times the thermic effect of either carbohydrate or fat -- meaning that it elevates metabolism ~5-10% higher than when either carbohydrate or fat are consumed.

Both carbohydrates and fats can be consumed (theoretically) in quantities greater than the daily energy expended because there is no physiological limit or ceiling that occurs when these substrates are metabolized. Excess dietary carbohydrate or excess fat do not make us acutely ill like excess protein. Hence, these excess calories are simply stored as body fat. Over the long haul, when more energy is consumed than energy expended, we gain weight.

Carbohydrates that cause us to gain weight are typically carbohydrates with a high glycemic load. Although most of you have probably heard of the glycemic index (the ability of a food to acutely raise the blood sugar), many are unfamiliar with the glycemic load, which is simply the glycemic index of a food multiplied by the carbohydrate content in a given amount of the food. The glycemic load of a food is more closely related to the net insulin response over a 24-hr period than is the simple glycemic index. Consequently, it is the glycemic load that may predispose us to obesity and chronic disease.

Although watermelon has a high glycemic index (72) similar to white bread (70), it has a glycemic load (per 100 grams of watermelon) that is only 5.2 compared to a glycemic load in white bread of 34.7. The International Table of Glycemic Indices lists the glycemic index of 11 fruits. The glycemic loads (per 100 grams of food) of these 11 fruits are as follows: bananas 12.1, pineapple 8.2, grapes 7.7, kiwi fruit 7.4, apple 6.0, pear 5.4, watermelon 5.2, orange 5.1, cherries 3.7, peach 3.1, grapefruit 1.9. Consequently one would have to eat 6.7 times as much watermelon as white bread to achieve an equivalent glycemic load. Let's say you ate 4 slices of white bread (or 100 grams, ~ 1/4 lb). In order to get an equivalent glycemic load, you would have to eat almost 1.5 lbs of watermelon or 4 lbs of grapefruit.

One of the body's mechanisms used to determine when to stop eating is stomach volume or fullness. Most people would stop eating watermelon after about 3.0 lbs (435 kcal) or say even 6.0 lbs (870 kcal) because their stomach volumes simply could not physically take much more food. Hence, under normal eating conditions, it is difficult or impossible for most people to overeat on fruits alone.

However, this being said there are some important exceptions. Dried fruits are not only concentrated calorie sources, they also represent high glycemic loads and have a high potential to cause weight gain, particularly when eaten in unlimited quantities. In addition, high-fat foods such as nuts, seeds, or fatty meats, if consumed in excessive quantity along with fruits, can also promote weight gain.

When I say unlimited quantities, perhaps I should say, within normal eating limits, rather than complete gluttony. If you are unsure of "normal limits" and do not know if you are hungry, then eat a piece of lean turkey breast. If you are still hungry, eat more lean protein, particularly if weight loss is a major objective.

Would you recommend the paleo diet also for small children? Any concerns or modifications needed?  What about pregnancy?

Little has been written about the dietary differences between adult and child hunter-gatherers. Also, very little is known about how a modern diet based upon "Paleo" food groups would influence growth and development in fully westernized children. Let me give you some key points which may be of use to you.

1.   Hunter-gatherer children typically had a much longer age at weaning than what is considered normal in the western world. Studies of five hunter-gatherer societies (!Kung, Ache, Inuit, Australian Aborigines, and Hadza) reveal the average age of weaning to be 2.9 years (Eaton SB et al. Women's reproductive cancers in evolutionary context. Quart Rev Biol 1994;69:353-67.). Hence, a hunter-gatherers early nutrition (birth -- 3 years of age) is highly dependent upon mother's milk. Because hunter-gatherers typically consumed a diet higher in n-3 fatty acids than westerners, mother's milk likely would also have been higher in n-3 fatty acids than milk from the typical nursing western mother. Numerous studies show that fetal and infant cognitive development requires sufficient n-3 fatty acids during pregnancy and the suckling period. For the western mother, weaning at age 3 is impractical, but should be carried out as long as possible (say maybe 1- 1.5 years). Following weaning, I recommend that infants be given a formula that is enriched with both DHA and AA. Infants should not be given EPA in the form of fish oil because it competes with AA metabolism and can result in impaired motor development as well as growth.

2.   Mother's milk contains very little iron, however infants are born with sufficient iron stores to last about 9-12 months before being depleted. In the western world, pediatricians typically recommend that infants receive their first solid foods as iron fortified cereals. An alternative is macerated meat (beef, pork, chicken) that is  available in commercial baby foods. Hunter-gatherer mothers introduced first foods to their infants by thoroughly masticating meat, marrow, nuts, seeds, fruits etc in their mouth, mixing it with saliva into a bolus and then giving their child this bolus. If you do give cereal to your infant, I would only recommend rice and do not recommend either wheat or oats.

3.   Virtually all pediatricians recommend that cow's milk and dairy products (yogurt, cheese etc) should be excluded from the infant's diet during the first year of life. Early exposure to milk and dairy products have been implicated with an increased risk of a number of autoimmune diseases -- particularly type 1 diabetes. I recommend that dairy products not be introduced until later -- at least until age 2.

4.   Once solid foods are introduced, I recommend focusing upon the basic types of foods that I recommend for adults (fresh fruits and veggies, fresh meats and seafood). There is some evidence that the liver of growing children is less able to deal with high levels of protein (~30-40 % total energy), so fattier meats and fish should not necessarily be restricted. Omega 3 enriched eggs should be the egg of choice and are a wonderful source of DHA. Infants and young children usually have no problem with scrambled eggs.  Also, fattier plant foods (nuts, avocados) and healthful oils are useful, although sometimes nut allergies present themselves.

5.   I do not advocate completely restricting processed food from children because eating involves behavioral issues that transcend the pure nutritional issues. We do not live as hunter-gatherers but rather as westerners in an industrialized world, and it is important to make children aware of good and bad food choices. The best way to get your child to eat junk food is to completely restrict it. In our household, we serve typical Paleo foods (fresh fruits, veggies, lean meats and seafood) at every meal and encourage our children to eat these foods. We stock very little processed food in the house, so if your children are hungry their choices are primarily healthy nutritious foods. We do not allow unlimited access to either TV or computers or electronic games, but rather encourage our children to be active in outdoor games and play. I believe that for active children certain high glycemic load foods, particularly during growth and development, may not be harmful. We do not restrict dried fruit (raisins, dates, etc), potatoes, and encourage consumption of bananas, yams and sweet potatoes.

6.   Because of metabolic changes that occur in the liver during pregnancy, women cannot tolerate as high protein levels as they normally could. This issue has been documented in both the anthropological and clinical literature. Hence fattier meats, and higher fat vegetable foods and more carbs are required.

7.   A final point that is somewhat of a double edged sword. In the western world, a tall child is considered a healthy child, and tall children frequently grow into tall adults. Most societies view being tall a very positive attribute in both children and adults. However, being tall has it's downside and increases the adult risk for a number of cancers, particularly breast cancer in women. Until recently the nature of this relationship has remained obscure. Our research group believes that the relationship between stature and cancer risk involves the consumption of high glycemic load carbohydrates during childhood along with an otherwise healthy diet, high in protein. If you download this paper from the Research Articles page (Cordain L, Eades MR, Eades MD. Hyperinsulinemic diseases of civilization: more than just syndrome X. Comp Biochem Physiol Part A 2003;136:95-112), I fully explain how high glycemic load carbohydrates both increase adult height and also increase the risk for numerous chronic diseases.

Most of the scientific data on ketogenic diets concerns the treatment of refractory epilepsy in children. Ketogenic diets have been shown to reduce the number of seizures and are routinely prescribed as a therapeutic modality for this illness. Ketosis is caused by the metabolism of dietary fat when carbohydrate is unavailable or during starvation. Ketosis elevates blood levels of two ketone bodies (d-beta-hydroxybutyrate and acetoacetate) which provide the brain with a non-glucose substrate, thereby sparing muscle from metabolic destruction for glucose synthesis -- remember, except for ketones, the brain can only use glucose as a fuel.

Side effects of ketogenic diets in epileptic children include: 1) refusal to drink fluids, 2) hypoglycemia, 3) lack of appetite, 4) nausea and vomiting, 5) elevations of blood cholesterol levels, 6) constipation, 7) anorexia, 8) metabolic acidosis, 9) kidney stones, and 10) deficiencies of the amino acid carnitine. See Rios G. Rev Neurol 2001;33:909-15.

I have addressed how The Paleo Diet influences a variety of hormonal cascades in Chapter 5 in my book, particularly as it relates to insulin resistance. The Paleo Diet tends to normalize insulin metabolism in most people because of its low-glycemic carbohydrates, its high protein content and its beneficial balance of omega-6 and omega-3 fatty acids. The normalization in insulin influences other hormonal pathways such as the IGF-1/IGFBP-3 and retinoic acid axis which in turn reduces the risk of many maladies associated with abnormal or unregulated tissue growth, as described in my book. Additionally, the high dietary levels of omega-3 fatty acids tend to produce a localized hormone (eicosanoids) profile that is anti-inflammatory.

I would be strictly speculating here because I believe there is no direct clinical evidence. However, one of the major problems of the ultra-low-carb diets are that they yield a net metabolic acidosis because there is insufficient alkaline base (only derived from fruits & veggies) to neutralize the net renal acid load that the kidney must deal with from a high-meat diet. As I have pointed out in question 2, there is some evidence that a net metabolic acidosis may elicit a mild primary hypothyroidism and hyperglucocorticoidism.

It depends upon the nature of the problem underlying the hypothyroid condition. If hypothyroidism stems from a tumor or specific metabolic disorder, then diet will be of little consequence. If the hypothyroidism stems from general ill health and is of an unknown etiology, then there is considerable evidence to suggest that the diet I have outlined may be therapeutic. Hypothyroidism has been frequently observed in Type 2 diabetics and may result partially from the endocrine changes that result from insulin resistance. Additionally, in animal models, low dietary protein can elicit low serum thyroxin levels. Further, millet (a common dietary cereal grain) found in the diet of Africans is known to be the underlying cause of endemic goiter in these people. Also, hypothyroidism occurs frequently in celiac patients suggesting that there may be an immune interaction with the gliadin fraction of wheat and the thyroid gland. Finally, a diet that produces a net metabolic acidosis (ala the standard grain, cheese, and salt-laden western diet) has also been associated with mild primary hypothyroidism and hyperglucocorticoidism.

Taken together this information suggests that a diet that is high in protein, of a low glycemic load, contains no cereal grains and produces a net alkaline load to the kidney may be of therapeutic value. Guess what -- these nutritional characteristics describe The Paleo Diet to a T!

I was wondering how you explain the benefits of the diet to those with severe hypertension and renal disease. High protein diets have a very high potential renal acid load. Even with a balance of fruits and vegetables, the protein would seem to add harmful strain on the kidneys.

Patients with pre-existing kidney disease and secondary hypertension as a direct result of this condition will worsen when given a high protein diet. This observation stems primarily from the work of Brenner and colleagues (1). Glomerulosclerosis elevates urinary albumin concentrations because of altered glomerular permeability. In patients with pre-existing kidney disease, reduced protein diets reduce GFR and urinary albumin. Brenner then took a leap of faith by suggesting that chronic high protein diets may underlie the development of glomerulosclerosis because they increase GFR which in turn induces nephrotic hyperfiltration causing glomerulosclerosis. The Achilles heel of this hypothesis is that elevated GFR from increased dietary protein had only been shown under short-term conditions (1-4 wks). At the time in 1982, no one had bothered to examine kidney function with chronic high protein diets in healthy normals. Arne Astrup's group finally got around to doing this experiment in 1999 in a randomized dietary intervention over a 6-month period comparing a high protein diet (25% energy) vs. a low protein diet (12% energy) (2). Kidney function remained normal; GFR expressed per unit kidney volume did not change, nor did albumin appear in the urine. The conclusion was, "Moderate changes in dietary protein intake cause adaptive alterations in renal size and function without indications of adverse effects."

1. Brenner BM, Meyer TW, Hostetter TH. Dietary protein intake and the progressive nature of kidney disease: the role of hemodynamically mediated glomerular injury in the pathogenesis of progressive glomerular sclerosis in aging, renal ablation, and intrinsic renal disease. N Engl J Med. 1982 Sep 9;307(11):652-9

2. Skov AR, Toubro S, Bulow J, Krabbe K, Parving HH, Astrup A. Changes in renal function during weight loss induced by high vs. low-protein low-fat diets in overweight subjects. Int J Obes Relat Metab Disord. 1999 Nov;23(11):1,170-7.

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My question is about exercise and hypoglycemia. When I got home from work this afternoon, I ate 2 fillets of tilapia and an orange. After about 25 minutes, I then began riding a stationary bike. When I had ridden for 26 minutes, my blood sugar all of the sudden took a nose dive: I became faint and light-headed. I ate an apple and a couple handfuls of walnuts and the symptoms disappeared within a few minutes.

Normally I don't have this problem. I do this type of exercise almost daily. But I usually eat an orange immediately before starting to exercise. Today, I didn't start exercising until almost a half-hour after eating. Was that the cause of my problem?

I believe that you experienced low blood sugar because of the reduced carbohydrate content of the diet compared to your former diet. First and foremost, listen to your body and if a piece of fruit and some nuts alleviates symptoms then do so.

I believe that one of the metabolic changes that eventually occurs on reduced carbohydrate diets is increased utilization of fat by working muscles. The two primary sources of this fat are 1) fat stores directly within muscle called "intra-muscular triglycerides" (IMT), and 2) free fatty acids in your bloodstream whose source is from stored fat in adipose (fat) tissue. When the typical western, high carbohydrate diet (bread, rice, potatoes, refined sugars etc) is consumed the muscles adapt to this diet by storing more carbohydrate within muscle cells as glycogen, and simultaneously storing less IMT. Additionally, high carbohydrate diets tend to reduce the enzymes that allow fat stores to be broken down and utilized during exercise. As your body becomes more and more accustomed to a reduced carbohydrate intake, both IMT stores will increase along with increased efficiency of stored fat breakdown. Thirdly, liver, blood and muscle glucose stores will be more actively conserved. The net effect of all of these changes will be to keep your blood sugar levels within normal ranges during exercise. I cant tell you specifically  how long these changes may take, but my co-author of my next book (The Paleo Diet for Athletes), Joe Friel, a U.S. Olympic triathlete coach, who has adopted the diet, indicated it took him 6-8 weeks.

In support of this notion (increased efficiency of fat utilization during exercise) is evidence from the Ache hunter-gatherers from Paraguay. My research colleague, Dr. Kim Hill from the Univ of NM has spent the last 30 years studying the Ache people and has gone along with the men as they hunt peccaries in the forests. Kim reports that the men frequently would get up in the morning, eat no breakfast and then chase after peccary herds, in hunts that could last 6-8 hours or more. During this time the Ache men took no food and only drank water during the extended chase. Kim said he tried to "run with the hunt" with the Ache men, but could never do it. He always had to have his breakfast to be able to keep up. He told me the Ache men would laugh at him. Apparently, these hunters have metabolic systems that make magnificent use of the fatty acid metabolic pathways. It would be interesting to measure IMT stores, and beta-oxidation pathways (fat breakdown) in the Ache and compare them to westerners.

Anyway, the bottom line is to listen to your body until it is fully adapted to this new way of eating.

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I heard or read recently that high-protein diets are detrimental to bone health. Is this true and how does it occur?  Will The Paleo Diet damage my bones or give me osteoporosis?

In the U.S. calcium intake is one of the highest in the world, yet paradoxically we also have one of the highest rates of bone de-mineralization (osteoporosis). Bone mineral content is dependent not just upon calcium intake but upon net calcium balance (calcium intake minus calcium excretion). Most nutritionists focus upon the calcium intake side of the calcium balance equation, however few realize that the calcium excretion side of the equation is just as important.

Bone health is substantially dependent on dietary acid/base balance. All foods upon digestion ultimately must report to the kidney as either acid or base. When the diet yields a net acid load (such as low-carb fad diets that restrict consumption of fruits and vegetables), the acid must be buffered by the alkaline stores of base in the body. Calcium salts in the bones represent the largest store of alkaline base in the body and are depleted and eliminated in the urine when the diet produces a net acid load. The highest acid-producing foods are hard cheeses, cereal grains, salted foods, meats, and legumes, whereas the only alkaline, base-producing foods are fruits and vegetables. Because the average American diet is overloaded with grains, cheeses, salted processed foods, and fatty meats at the expense of fruits and vegetables, it produces a net acid load and promotes bone de-mineralization. By replacing hard cheeses, cereal grains, and processed foods with plenty of green vegetables and fruits, the body comes back into acid/base balance which brings us also back into calcium balance.

The Paleo Diet recommends an appropriate balance of acidic and basic (alkaline) foods (i.e., lean meats, fish and seafood, fruits, and vegetables) and will not cause osteoporosis in otherwise healthy individuals. Indeed, The Paleo Diet promotes bone health.

For additional reading on this subject, navigate to the Articles page, The nutritional characteristics.... and Acid/Base Balance table.

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What's the problem with adding salt to my food?

As do hard cheeses, cereal grains, meats, and legumes, salt presents a net acid load to the kidneys in the absence of alkaline foods such as fruits and vegetables. The body responds by tapping its reserve of calcium salts in the bones, which can lead to osteoporosis and other degenerative diseases. As described in The Paleo Diet, cheeses, grains, and legumes are nutritionally problematic for other reasons as well. Eating lean, low-salt meat is fine when it's balanced with fruits and vegetables. Do your body a favor and put the salt shaker away.

Research shows that sodium (Na⁺) adds alkaline ash and chloride (Cl^-) adds acid ash to the diet. How is table salt acid?

I refer you to my colleague Tony Sebastian's paper demonstrating that virtually all high-protein, pre-agricultural diets were net base yielding. A portion of this paper should answer your question as to why NaCl is net acid yielding.

Sebastian A, Frassetto LA, Sellmeyer DE, Merriam RL, Morris RC Jr. Estimation of the net acid load of the diet of ancestral preagricultural Homo sapiens and their hominid ancestors. Am J Clin Nutr. 2002 Dec;76(6):1308-16.

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The fat quality and quantity in the wild animals our Stone Age ancestors ate was vastly different from the types and quantity of fat found in the fatty meats typically consumed in the US. A 100-gram serving of roast buffalo contains only 2.4 grams of fat, and 0.9 g of saturated fat, whereas a 100-gram, T-bone beefsteak contains a whopping 23 grams of fat, and 9 grams of artery clogging saturated fat. Additionally, the bison roast contains 215 mg of heart-healthy, omega-3 fatty acids whereas the T-bone steak contains a paltry 46 mg. The types of meats permitted on The Paleo Diet are lean meats (beef, pork, poultry, fish, seafood) trimmed of visible fat. These meats are healthful because they have nutritional characteristics similar to wild animals.

Recent clinical studies have shown that lean protein-based diets are more effective in improving blood cholesterol and other blood lipid levels than are low-fat, high-carbohydrate diets. High protein diets have also been shown to lower blood homocysteine levels, another risk factor for heart disease. When nutritionists abandoned meats as part of heart-healthy diets, they unknowingly threw out the baby with the bath water. It was the saturated fat that accompanied the lean protein that was harmful -- not the lean protein itself.

What would you say to people who disagree with your assertion that saturated fats cause heart disease?

First off, let's get the record straight. I have never said that saturated fats are the sole dietary cause of "heart disease."  Coronary heart disease (CHD) consists of myocardial infarctions (heart attacks) and angina pectoris and accounts for 54% of the deaths from a larger category of heart and blood vessel illnesses called cardiovascular disease (CVD) which accounts for 40.6% of all deaths in the U.S. CVD not only includes CHD, but also stroke, congestive heart failure, hypertension, rheumatic heart disease, congenital cardiovascular defects, artery diseases and others. The physiological mechanism underlying CHD is atherosclerosis, a complex process involving interactions among environmental factors (both nutritional and non-nutritional) and the genome. Environmental factors such as exercise, smoking, and inflammation clearly influence the development and progression of atherosclerosis. Numerous nutritional factors can serve to either (1) promote or (2) inhibit atherosclerosis via modulation of one or more of the steps involved in the atherosclerotic process.

Dietary saturated fats are nutritional elements that may promote atherosclerosis. As consumption of certain saturated fatty acids (12:0, 14:0, 16:0, but not 18:0) increases, the number of hepatic (liver) and peripheral low-density lipoprotein (LDL) receptors decreases which in turn causes serum concentrations of LDL cholesterol to rise (a process called down regulation). Down regulation occurs because internalization of 12:0, 14:0 and 16:0 within cells reduces the expression of genes which code for the LDL receptor protein. At low blood LDL cholesterol concentrations (20-50 mg/dl), LDL cholesterol molecules move freely in and out of the arterial intima (the portion of the artery where atherosclerosis arises). When blood levels of LDL cholesterol molecules rise, LDL molecules tend to become "stuck" in the intima where they undergo oxidation and glycation to become "modified LDL."  Modified LDL stimulates arterial endothelial cells to display adhesion molecules which latch onto circulating monocytes and T cells. The endothelial cells then secrete chemokines which bring the monocytes and T cells into the intima where they mature into macrophages. T cells release cytokines causing inflammation and cell division within the artery. The macrophages are different from all other cells in the body in that they display a scavenger receptor which is not down regulated by LDL cholesterol molecules. The macrophages "feast" upon modified LDL cholesterol in the intima and become filled with these fatty droplets and become foam cells. Cytokines cause smooth muscle cells to grow over the lipid core of multiple foam cells forming a tough fibrous cap which becomes the characteristic plaque which defines atherosclerosis. Finally, inflammatory cytokines secreted by foam cells weaken the fibrous cap by digesting the collagen matrix. If the weakened cap ruptures, a substance secreted by the foam cells called "tissue factor" interacts with clot promoting elements in the blood causing a thrombus (clot) to form. If the clot is large enough to halt blood flow, it causes a myocardial infarction (heart attack).

Dietary saturated fats do not always elevate blood LDL concentrations. When consumed under hypocaloric (reduced energy) conditions they may improve most blood lipid parameters including total and LDL cholesterol, HDL cholesterol, and total triacylglycerol (TG). This phenomenon typically explains why Atkins-like diets (such as recently reported this spring in the New England Journal of Medicine) may be as or more effective than hypocaloric, low-fat, high-carbohydrate diets. However, under isocaloric (normal energy) conditions, studies of healthy normal subjects show increased consumption of saturated fats significantly raises blood LDL concentrations.

A further confounding factor in this scenario is the presence of a specific type of LDL cholesterol molecule in the blood called "small dense LDL."  The rate of influx of LDL into the intima is not only related to the blood concentration of LDL cholesterol, but also to the size of the LDL molecule. Small dense LDL have a greater flux into the intima than normal LDL and they are more likely to get "stuck" in the intima because of increase binding to proteoglycans. The primary metabolic source of small dense LDL is very low density lipoprotein molecules (VLDL) whose blood concentration is greatly influenced by dietary carbohydrate, particularly high-glycemic-load carbohydrates. Hence foods with high glycemic loads such as those made with refined sugars and grains may also operate synergistically with high dietary saturated fats to promote atherosclerosis. Additionally, high-glycemic-load carbohydrates are positively correlated with plasma concentrations of C reactive protein, an important marker for systemic inflammation, a key element of the atherosclerotic process, as I previously noted.

The gold standard procedure for demonstrating cause and effect between diet and disease is called a dietary intervention. Subjects are either fed or not fed a certain food or nutrient and then either presence or absence of a disease or disease symptom is monitored over time. With CHD, the results of dietary interventions in which saturated fats have been lowered, frequently have been unable to demonstrate a reduced mortality from CHD. The problem with the majority of these studies is that they were conducted prior to the knowledge that high-glycemic-load carbohydrates were an important promoting factor in CHD etiology. Further, most of these studies did not control for inhibitory dietary factors such as omega-3 fatty acids, fiber, phytochemicals, antioxidants etc. Hence, the interpretation of whether or not dietary saturated fats cause CHD in these interventions is confounded by a number of crucial variables. In animal studies, including primates, these confounding dietary factors can be completely controlled and atherosclerosis is routinely induced by solely feeding high amounts of saturated fats.

Excellent point. We need more information to determine if very-low-carbohydrate, high-fat diets reduce small-dense LDL in all people or only in certain genetically predisposed people ala the multiple studies done by Dreon et al. Further it will be necessary to determine whether or not the total increase in LDL (even with a concomitant decrease in small-dense LDL) still accelerates the atherosclerotic process. It seems most likely that small-dense LDL is derived from triacylglycerols carried in the VLDL fraction, hence the possibility looms that a major determinant of atherosclerosis is the ratio of total LDL/small-dense LDL. To my mind, the evidence points to the notion that atherosclerosis results from many environmental factors including those dietary elements that simultaneously raise LDL (high-saturated-fat diets) and triacylglycerols (high-glycemic-load diets). Both of these dietary characteristics could not have been part of any Paleolithic diet.

Why do you recommend eating lean meats?  Wouldn’t hunter-gatherers have savored fatty meats?

Some people who have adopted what they think are "Paleolithic diets" have embraced fatty meats such as bacon, T-bone steaks, and ribs as staple meats. Even some of the Diet Doctors with their high-fat, low-carbohydrate weight loss schemes have tried to jump on the Paleolithic bandwagon by suggesting that fatty meats would have been normal fare for Stone-Agers. Let’s take a look at the real story.

Because animals had yet to be domesticated, Stone Age hunters could only eat wild animals whose body fat naturally waxes and wanes with the seasons. In contrast, virtually all of the meat in the typical U.S. diet comes from grain-fattened animals, slaughtered at peak body fat percentage regardless of the time of year. For instance, modern feedlot operations typically produce an obese (30% body fat or greater) 1,200-pound steer ready for slaughter in about 14 months. These animals are produced like clockwork, 12 months out of the year, no matter whether it is spring, summer, fall or winter. Quite the opposite, the first figure below shows how body fat changes with the seasons in wild animals such as caribou. Note that for 7 months out of the year total body fat averages less than 5.0 %. Only in the fall and early winter are significant body fat stores

present, but you can see from the figure that these values are 1/2 to 2/3 less than the obese (30% fat) feedlot produced steer!

Even more telling is how the types of fat change seasonally in the carcass of wild animals. Remember, hunter-gatherers ate everything--all edible body parts except, bones, hooves, hide, and horns were relished. By analyzing the total amount of fat and the kinds of fat in muscle, storage fat, and all of the edible organs, our research team at Colorado State University was able to show how the animal’s total body content of saturated fat varied with the seasons. Take a look at the figure below and you can see that for 7 months out of the year,

the saturated fat from the total edible carcass averages only 11.1 percent of its total available calories--meaning that hunter-gatherers simply did not have a high, year-round dietary source of saturated fat. To lower our blood cholesterol levels and reduce the risk of heart disease, the American Heart Association recommends that our dietary saturated fat intake should be 10% of our total daily calories--a value remarkably close to what hunter-gatherers could have obtained from eating wild animals on a year round basis!  For this reason, we recommend that you always eat the leanest cuts of meat.

There is absolutely no doubt that hunter-gatherers favored the fattiest part of the animals they hunted and killed. As far back as 2.5 million years there is incredible fossil evidence from Africa showing this scenario to be true. Stone tool cut marks on the inner jawbone of antelope reveal that our ancient ancestors removed the tongue and almost certainly ate it. Other fossils show that Stone Age hunter-gatherers smashed open long bones and skulls of their prey and ate the contents. Not surprisingly, these organs are all relatively high in fat, but more importantly analyses from our laboratories showed the types of fats in tongue, brain, and marrow are healthful, unlike the high concentrations of saturated fats found in fatty domestic meats. Brain is extremely high in polyunsaturated fats including the health-promoting omega-3 fatty acids, whereas the dominant fat in tongue and marrow are the cholesterol lowering monounsaturated fats.

Since most of us would not savor the thought of eating brains, marrow, tongue, liver, or any other organ meat on a regular basis, a few 21^st century  modifications of the original Paleolithic diet are necessary to get the fatty acid balance "right."  First, we suggest that you limit your choice of meats to very lean cuts, but don’t worry about fatty fish as they are good for you just like the organ meats our ancestors preferred.  Secondly, we recommend that you add healthful vegetable oils (e.g., canola, olive, flax) into your diet. By following these simple steps, together with the other nuts and bolts of this plan, the fatty acid balance in your diet will approximate what our Stone Age ancestors were getting.

So, how much fat were they getting and what types of fat did they eat?  As I mentioned earlier, there was no single Stone Age diet, but rather diet varied by season, locale, and food availability. From our analyses of 229 hunter-gatherer diets and the nutrient content of wild plants and animals, our research team has demonstrated the most representative fat intake would have varied from 28 to 57% of total calories. To reduce our risk of heart disease, the American Heart Association recommends that we should limit our total fat to 30% or less of our daily calories. On the surface, it would appear that, except for the extreme lower range, there would be too much fat in the typical hunter-gatherer diet. Well, this is the same message that we (the American public) have heard for decades--get the fat out of your diet!  The Food Pyramid cautions us to cut as much fat as we can and replace it with grains and carbohydrate. Not only is this message misguided, it is just flat out wrong. Scientists have known for more than 50 years that it is not the total amount of fat in the diet that promotes heart disease but rather the kind of fat. Plain and simple, it is a qualitative issue, not a quantitative one!  Polyunsaturated fats are good for us, particularly when we correctly balance the omega-3 and omega-6 fatty acids. Monounsaturated fats are heart healthy, and even some saturated fats such as stearic acid (found in animal fat) do not promote heart disease. Deadly fats are three specific saturated fats (palmitic acid, lauric acid, and myristic acid) and the trans-fats found in margarine, shortening, hydrogenated vegetable oils, and processed foods made with these products.

Now let’s get back to the fat content of our ancestral hunter-gatherer diet.  They frequently ate more fats than we do, but they were almost invariably healthy fats. Using computerized dietary analyses of the wild plant and animal foods, our research team has shown that the usual fat breakdown in hunter-gatherer diets was 55-65% monounsaturated fat, 20-25% polyunsaturated fat (with an omega-6:omega-3 ratio of 2:1), 10-15% saturated fat (with about half being the neutral stearic acid). This balance of fats is exactly what you will be getting when you follow our dietary recommendations.

We have recently analyzed and compared the fatty acid composition of wild animals, grass-fed beef, and grain-fed beef (Cordain L et al. Eur J Clin Nutr 2002;56:181-91) and have found that the relative saturated fat content within subcutaneous fat (be it from grain-fed cows, grass-fed cows, or wild game) is virtually identical among the three different animals. However, the absolute amount of saturated fat is two to three times higher in the meat (muscle) of grain-fed cows. Consequently, if you would like to reduce your intake of saturated fat (which I believe to be a prudent dietary measure), then excess fat should also be trimmed from grass-fed beef meat (muscle). The healthful long-chain (>20 carbon) omega-3 fatty acids are found almost exclusively within the phospholipid fraction of the muscle membrane.

On pages 127-129 of my book, I outline the differences in the fatty acid composition of the various cooking and salad oils that are available to consumers. I recommend canola oil because it is high in monounsaturated fats (58.9%), low in saturated fats (11.6%) and has an omega-6/omega-3 ratio (2.0) that mimics the ratio found in pre-agricultural diets. These fatty acid characteristics have been shown in numerous clinical trials to reduce the risk of atherosclerosis and heart disease, currently the number one cause of death in the U.S.

Canola oil comes from the seeds of the rape plant (Brassica rapa or Brassica campestris) which is a close relative of broccoli, cabbage, Brussels sprouts and kale. Humans have eaten cabbage and its relatives since prior to historical times. In its original form, rape plants produced a seed oil that contained high levels (20-50%) of a monounsaturated fat called erucic acid (22:1n9) that was shown to cause a wide variety of pathological changes in laboratory animals. In the early 1970's plant breeders from Canada developed a strain of rape plant that produced a seed with less than 2% erucic acid (hence the name canola oil). The erucic acid content of commercially available canola oil averages 0.6%. Numerous animal experiments show that the previous health effects identified with high concentration of erucic acid do not occur at this concentration, and in fact canola oil prevents potentially fatal heart arrhythmias in animal models. There is no credible scientific evidence showing that canola oil is harmful to humans.

The following quote was taken from Loren Cordain and James O'Keefe's Cardiovascular Disease Resulting From a Diet and Lifestyle at Odds With Our Paleolithic Genome: How to Become a 21st-Century Hunter-Gatherer: "Trans fatty acids are also found in shortenings, most margarines, and deep-fried foods, and recently in many brands of commercially available canola oils."  How does this reconcile with your recommendation to use canola oil?

Recently it has been shown that the deodorization process used during the manufacture of many vegetable oils produces a trans isomer of 18:3n3 (alpha linolenic acid) (1). This isomer varies from 18:1n9 trans (trans elaidic acid) which is the chief trans fatty acid produced during the hydrogenation of vegetable oils to produce margarine and shortening. The biological effects of trans ALA isomers are not as well known as 18:1n9 trans, but they do produce undesirable changes in the lipid profile (1). A naturally occurring trans fatty acid (18:1n11 trans or trans vaccenic acid) is present in the meat, milk and cheese from all ruminants. Little is known about it's biological effects, but generally it seems to be benign.

The deodorization process of canola oil, or soybean oil, doesn't always yield trans isomers of ALA, and careful deodorization processing prevents the formation of trans ALA (1,2). When purchasing canola oil, choose brands with labels guaranteeing freedom from trans fatty acids.

1. Vermunt SH, Beaufrere B, Riemersma RA, Sebedio JL, Chardigny JM, Mensink RP, TransLinE Investigators a. Dietary trans alpha-linolenic acid from deodorised rapeseed oil and plasma lipids and lipoproteins in healthy men: the TransLinE Study. Br J Nutr. 2001 Mar;85(3):387-92.
2. Henon G, Kemeny Z, Recseg K, Zwobada F, Kovari K. Deodorization of vegetable oils. Part I: Modeling the geometrical isomerization of polyunsaturated fatty acids. Journal of the American Oil Chemists Society 76, 73-81.

In his book, Loren lists nuts based on the goodness of their omega-6:omega-3 ratio. He says the ratio should be 2 or 3:1. Walnuts are the best at I think something like 2:1, and he says MAYBE macadamia nuts are okay at 6:3. The other nuts go down from there. I'm no math whiz, but isn't 6:3 pretty much 2:1?

On page 125 & 126 of my book, I list the n6/n3 ratios of commonly consumed nuts. Walnuts are best with a ratio of 4.2:1, followed by macadamia nuts with a ratio of 6.3:1. So macadamia nuts have a little more than six times the amount of n6 fatty acids than n3 fatty acids. We estimate that in Stone Age diets people would have had a net dietary n6 to n3 ratio of between 2-3:1. Consequently, high consumption of nuts can swing the n6/n3 balance too high in favor of n6 fatty acids.

All oils become partially oxidized when heated and produce secondary lipid compounds. The amount of oxidation produced is dependent upon the type of oil, the temperature, and the length of heating. Generally, the fewer number of double bonds (or greater degree of saturation), the more stable is the oil to heat. Saturated fats have no double bonds and are more heat stable than monounsaturated fats (with a single double bond) which in turn are more stable than polyunsaturated fats (multiple double bonds). Flaxseed oil contains 20% monounsaturated fat, 66% polyunsaturated fat (mainly alpha-linolenic acid [53% energy]) and 9.4% saturated fat. Studies of ground flaxseed during cooking at temperatures encountered during baking (350 degrees F for 2 hrs; 400-425 F for 20-25 min or 662 F for 60 min) show that there is no degradation of the alpha-linolenic acid to oxidized secondary lipid compounds (Flax Council of Canada). However, I have recently learned, after publication of my book, that a distinction must be made between flaxseed and flax oil. For reasons that are unclear, flax oil must not be used during cooking. Flax oil should be added to meats and sauces after cooking. I certainly do not recommend frying food with flaxseed or any other oil under searing or high heat. You can achieve the healthful benefits of flax oil by applying the oil to meats after cooking is complete. The main issue here is that omega-3 fats are healthful fats and the more ways that you can include them in your diet, the better off you will be. The risk to your health by consuming small amounts of oxidized lipids is infinitely smaller than the risk to your health by not consuming omega-3 fatty acids.

Virtually all metabolic chamber studies examining the ability of the three macronutrients (protein, carbohydrate, fat) to boost metabolism are in agreement that protein has two to three times the thermic effect (ability to boost metabolism) of either fat or carbohydrate. I am unaware of any evidence contrary to these established facts.

I have a question dealing with fatty acids and human brain development: Many Paleo Diet researchers (Cordain, Broadhurst, Cunnane,) think that an increased energy density of food and an increased supply with DHA (fish, brain) was necessary for human brain development. This idea will also be discussed in the forthcoming 71st annual meeting of the American Association of Physical Anthropologists (see http://www.physanth.org/annmeet/aapa2002/ajpa2002.pdf : abstracts from Cordain: p. 57; Broadhurst p. 49). On the other hand vegans have a normal brain development without any DHA from animal resources. My question: Can a factor that is not necessary in ontogenesis really be a necessary factor for phylogenesis?

Numerous studies of vegan vegetarian mothers show that DHA is reduced in both the tissues of mother and newborn infant and that reduced plasma concentrations of DHA is associated with both behavioral, cognitive, and visual problems in the developing child/infant when the child/infant is deprived of preformed DHA. Hence DHA is indeed necessary during ontogenesis.

Also, remember that the brain continues to grow in all primates long after the weaning period -- more so than in any other altricial mammal. Hence, additional DHA in the diet (via increased animal food ingestion) allows for the increased accretion of DHA in the brain over time. In precocious mammals brain and body growth occurs rapidly, consequently even if exogenous DHA is available there is little or no time for accretion.

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On a calorie-by-calorie basis, whole grains are lousy sources of fiber, minerals, and B vitamins when compared to the lean meats, seafood, and fresh fruit and veggies that dominate The Paleo Diet. For example, a 1,000-calorie serving of fresh fruits and vegetables has between two and seven times as much fiber as does a comparable serving of whole grains. In fruits and veggies most of the fiber is heart-healthy, soluble fiber that lowers cholesterol levels -- the same cannot be said for the insoluble fiber that is predominant in most whole grains. A 1,000-calorie serving of whole grain cereal contains 15 times less calcium, three times less magnesium, 12 times less potassium, six times less iron, and two times less copper than a comparable serving of fresh vegetables. Moreover, whole grains contain a substance called phytate that almost entirely prevents the absorption of any calcium, iron, or zinc that is found in whole grains, whereas the type of iron, zinc, and copper found in lean meats and seafood is in a form that is highly absorbed.

Compared to fruits and veggies, cereal grains are B-vitamin lightweights. An average 1,000 serving of mixed vegetables contain 19 times more folate, five times more vitamin B6, six times more vitamin B2 and two times more vitamin B1 than a comparable serving of eight mixed whole grains. On a calorie-by-calorie basis, the niacin content of lean meat and seafood is four times greater than that found in whole grains. Click here to read more about cereal grains.

I am one of many the people who has liked your work on Paleolithic diets however I recently came upon an article which seems to undermine the basic premise that Paleolithic human rarely if ever ate grains. The first article was found here: http://www.news.harvard.edu/gazette/daily/2004/07/07-grain.html

I also found references to this peer reviewed study upon further searching. The article by Dolores R. Piperno, Ehud Weiss, Irene Hoist & Dani Nadel, "Processing of wild cereal grains in the Upper Paleolithic revealed by starch grain analysis," Nature 430 (2004), seems to indicate that mixed farming quite common as far back as 23,000 years ago.

Doesn't this new evidence greatly undermine your argument at www.beyondveg.com that their hasn't been enough time for human adaptation to the Neolithic food sources aka cereal grains? I am just wondering what you think about those articles.

I am quite familiar with the recent paper in Nature, and it in no way changes the basic premise that Paleolithic hominins rarely or never consumed cereal grains. Remember that the Paleolithic period extends from the first appearance of stone tools (2.6 million years ago) until the beginning of agriculture 10,000 years ago. As I have stated in a number of publications, cereal grains are minimally digestible without milling (grinding) and cooking. The milling serves to breakdown the cell walls and cooking gelatinizes the starch thereby making both the starch and protein within the grain digestible inside the human GI tract.

Although a recent report suggests that hominins may have controlled fire by as early as 700,000 years ago, the best direct evidence for controlled fire use (hearths) do not appear regularly in the fossil record until ~250,000 to 300,000 years ago. Hence, for ~ 90% of the time hominins were present on the planet, cooking would not have been possible and accordingly cereal grains would have been minimally digestible had they been put in the mouth raw.

More relevant is the first appearance of the primitive stone processing tools (saddle stones, mortars, grinding holes etc.) in the fossil record. It has been generally known that these grinding tools first appeared in the upper Paleolithic (40,000 to 10,000 years ago), however until the Nature report, their function had not been directly linked to processing cereal grains. In fact, the evidence shows that in Europe these tools were used to grind soft stones to make ochre (a red dye). Prior to the Nature report, the earliest direct evidence linking grinding tools to grain processing was in the Natufian culture dating to 13,000 years ago. Consequently, the Nature report is important in that it pushes back cereal grain consumption by at least 10,000 years.

However, there are a couple of  key points that are relevant. First, no where else in the world except for the Levant is there any evidence for cereal grain consumption at this early date -- not in Europe, not in Asia and not in Africa. Secondly, because cereal grains were not domesticated until 10,000 years ago, grains could have only been consumed seasonally a few weeks out of the year, and would not have been staple foods. Additionally, wild wheat and barley were indigenous to a rather small geographic locale in the middle east and would not have been available to the world's people until after their domestication. Finally, 23,000 years ago, although it may seem historically remote represents less than 1.0 % of the time hominins have resided on earth. Consequently, for 99% of the evolution of virtually all hominins, cereals grains were not part of the diet.

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Coprolites are fossilized fecal remains and, except for bones and feathers, do not contain any digestive remnants of animal flesh and organs. Consequently, coprolites almost universally can only reveal the plant food types in the diet and cannot quantitatively show the relative amounts of plant and animal food proportions. Stable isotope studies of the collagen in Stone Age humans (living in England 13,000 years ago) show that their diet (in terms of protein content and quality) was indistinguishable from top-level trophic carnivores such as foxes and wolves.

Would you care to comment about Sally Fallon’s negative review of your book at the Weston A. Price website?

Needless to say, Sally Fallon's review bothers me -- not from a personal basis, but rather because it attempts to cloud the real dietary issues for readers like you, who may not have a sufficient background to know what is factual and what is hype. Further, this review attempts to discredit a very powerful new scientific concept (evolutionary medicine) that is being used worldwide by scientists in a wide variety of disciplines to answer complex health questions.

I do not know Sally Fallon, but I suspect that she has "an axe to grind" because of a debate I had with her co-author, Mary Enig, on whether or not dietary saturated fats were healthful or harmful. My research group and I believe that the high amounts of dietary saturated fats in the western diet promote atherosclerosis because they down-regulate the LDL receptor (a concept for which the Nobel prize in medicine was awarded in 1984). We do not believe that dietary saturated fats are the sole or even main cause of atherosclerosis, but rather are a part of many dietary elements that promote heart disease.

It is natural and healthy for scientists to disagree on scientific and medical issues as this is the process called "peer review" which ultimately moves science forward. Unfortunately, the internet is not a peer reviewed forum, and literally anyone can say anything they care to say. As far as I am aware, Sally Fallon is not a scientist, nor has she ever submitted any of her ideas to the peer review process in scientific journals. Does this mean that Sally Fallon's ideas have no merit?  No, they simply have not been adequately tested using the scientific method. All of the information I present in my book is substantiated by peer reviewed scientific articles that I have published, along with my research group or by other scientists from diverse fields.

Sally Fallon's review attempts to debunk the Paleo Diet concept by using a satirical tone in which she misleads the reader by taking information out of context and emphasizes specific points without examining the larger picture. The first paragraph of her review represents an example of this deliberately misleading prose. There is no doubt that hunter-gatherers ate the entire edible carcass of animals that were hunted and killed, and the fatty portions of the carcass were relished more than the lean muscle tissue. We have pointed this information out in many of our scientific papers. However, there are two key points that Fallon fails to mention.

The first is the total fat content of wild animal carcasses varies seasonally throughout the year in a cyclic waxing and waning manner. Studies of caribou over a 12-month period show that the total carcass (organs and all) fat  by weight for 7 months of the year average less than 5 %; for 9 months of the year it average less than 10 %. For 3 months of the year total carcass fat falls between 11-17 %. In contrast 99 % of the beef in the U.S. is produced under fed lot conditions in which the animal is always slaughtered at the peak or highest body fat % which typically exceeds 30 % by weight. An animal that has a body fat of 5% by weight equals 34 % fat by energy, whereas an animal that has a body fat of 30 % by weight equals 85 % fat by energy. Hence the total fat content of feed-lot produced domesticated animals is not even remotely close to that of wild animals.

The second point of deception in Fallon's review revolves around the types of fats available in the total edible carcass of wild animals over a 12 month period. From our recent paper analyzing the fat content in the tissues of wild animals (see webpage for article), we have been able to show that the dominant fats (> 50 % energy) in organs are polyunsaturated (PUFA) + monounsaturated (MUFA) fatty acids, whereas the dominant (>50% energy) fat in adipose tissue is saturated fat. Further, by employing allometric regressions that scale organ mass to tissue mass and then by analyzing the fat content and fatty acid composition of each organ, it is possible to calculate the total edible carcass fatty acid composition as it varies throughout the year. Our results (in press) show that for 9 months or more of the year, it would have been impossible to obtain >10 % of the total carcass energy as saturated fats.

In my book, The Paleo Diet, it was not my objective to precisely and exactly imitate the dietary practices of our hunter-gatherer ancestors, but rather to synthesize a diet from commonly available modern foods that would emulate the nutritional characteristics of hunter-gatherer diets. Few modern people would be willing to eat brains, intestines, liver, kidney, gonads, lungs etc. Nor do few modern, westernized people have access to wild animal meat and organs on a year round basis.   By removing skin and excess fat from domestic meats available at the supermarket and then by adding in healthful oils, it is possible to simulate the entire carcass fatty acid profiles of wild animals. Consumption of the fatty cuts of meat (chicken with skin, hamburger, beef ribs etc) on a year round basis is vastly at odds with the nutritional patterns of hunter-gatherers. It’s not that hunter-gatherers didn’t want to eat fatty meats; it’s just that a year round source did not exist. Hence, my recommendation to eat lean meats trimmed of visible fat along with healthful oils provides a diet with approximately 10 % or less of total energy from saturated fats - a value that mimics values in hunter-gatherer diets. From our paper (Cordain L. The nutritional characteristics of a contemporary diet based upon Paleolithic food groups. J Am Nutraceut Assoc 2002; 5:15-24), you can examine in more detail the fat profile of modern diets based upon Stone Age food groups.

The second paragraph of Fallon’s critique again represents a satirical ploy to invalidate the entire concept of evolutionary nutrition based upon irrelevant information.  In the first place Paleolithic people (hominins living during the Old Stone Age - approximately 2.4 million years ago until 10,000 years ago) did not cook in pots as pottery was first produced ~9,000 years ago. Secondly, oil extraction from any plants is not known to have occurred until ~ 6,000 years ago. But again, even though Fallon is unaware of this information, it skirts the real issue. It is virtually economically impossible or culturally deplorable for most western people to eat the entire carcass of wild animals throughout the year. Consequently certain beneficial changes must be made to foods commonly available at the supermarket to achieve the general nutritional characteristics of pre-agricultural diets. The addition of canola oil to lean domestic meats increases the MUFA and n-3 concentrations of the entire meal so that it more closely resembles the fatty acid concentrations that are present when the entire carcass of a wild animal is consumed. The addition of various spices, lemon juice etc. improves the flavor of the meat and makes it more palatable. Although this combination of spices certainly would not have been available to historically studied hunter-gatherers, there is extensive ethnographic evidence to show that various spices and plant parts were components of Holocene hunter-gatherer diets. The addition of these spices in no way impairs the nutritional qualities of the diet and in fact may add many valuable phytochemicals and antioxidants.

In the typical western diet refined sugars comprise 16-18% of the total daily energy. Clearly, there are numerous health problems associated with this enormous intake of empty calories. However, for many people it is difficult to make sudden behavioral changes, particularly when it comes to comfort foods, such as highly sugared processed foods (ice cream, cake, cookies, candy etc). Although fruits would be a much better choice for taming the sweet tooth, diet sodas can help people to make this transition. We never have suggested that diet sodas were part of pre-agricultural diets, but neither were fatty meats, milk, butter, cheese, whole grain breads or the salted foods that Fallon so highly recommends.

The third paragraph of Fallon’s diatribe becomes personal and insulting - not just for me for any educated person. I prefer to let the data and information speak for itself, regardless of a person’s gender, racial background or academic affiliation. Information should not be accepted or rejected upon who generates it, but rather upon the merit and objectivity of the idea. I personally find it repulsive to prejudice an individual or person based upon personal issues or characteristics that are unrelated to the information being presented.

In the third paragraph of her review, Fallon once again mistakenly suggests that we indicated that hunter-gatherers ate low fat diets. This never has been the case. Apparently, she has not bothered to read our paper (Cordain L, Brand Miller J, Eaton SB, Mann N, Holt SHA, Speth JD. Plant to animal subsistence ratios and macronutrient energy estimations in world wide hunter-gatherer diets. Am J Clin Nutr 2000, 71:682-92) in which we say "Our analysis showed that whenever and wherever it was ecologically possible, hunter-gatherers consumed high amounts (45-65% of energy) of animal food. And "the fat intake would be comparable or higher (28-58% energy) than values currently consumed in modern, industrialized societies."

Fallon brings up the notion of political correctness (pc) in her review. As scientists, we utilize the scientific method to form and test our hypotheses and let the chips fall where they will regardless of any pre-conceived notions. Although it may be politically correct to state that saturated fats are not necessarily healthful when consumed in the high amounts in the typical U.S. diet, it is terribly politically incorrect to recommend limiting grains of any kind (whole or processed) or dairy products. Our dietary recommendations have no basis in political correctness, but rather reflect what the data indicate.

In Fallon’s 4^th paragraph she completely misleads the reader by stating that: "He says that Paleolithic peoples had no carbohydrate foods like grains or starchy root foods—never mind reports of grains found in the fire ashes of some of the earliest human groups, or the widespread use of tubers among primitive peoples, usually fermented or slow cooked." This statement steps far beyond the bounds of truth. We go on record as stating that Pre-Agricultural people ate few or no grains, however we have never suggested that they did not eat tubers. Again, if Fallon would take the time to read our scientific papers, she would be aware of this. In our AJCN 2000 paper (Table 3) we show that tubers, roots and bulbs would have comprised 23.6 % of all the plant food consumed by the average hunter-gatherer. Grains are virtually indigestible unless the cell walls are broken via (grinding or milling) and the starch is gelatinized by cooking. Hence the appearance of stone grinding tools (mortar and pestle, saddle stones etc) heralds the widespread use of grains in hunter-gatherer societies. The first primitive grinding tools do not make their appearance anywhere in the world until the late Paleolithic (~15-20,000 years ago), and the first hunter gatherer society known to have made wide scale use of grains were the Natufians who lived in the Levant ~13,000 years ago.

The next statement in this paragraph is highly objectionable, false and is totally ignorant of the actual data regarding the fatty acid composition of the tissue of wild animals. "He says that there isn’t much fat in wild animals (did he check with any hunters while writing his book?) and that what fat these animals had was highly politically correct—low in "lethal" saturated fat and rich in monounsaturates and omega-3 fatty acids. Did he look up the fatty acid profile of buffalo fat while researching his book? Obviously not. If he had, it would have ruined his whole theory because buffalo fat is more saturated than beef fat."  Apparently, Fallon again has failed to do her homework. If she would take the time to read our paper (Cordain L, Watkins BA, Florant GL, Kehler M, Rogers L, Li Y. Fatty acid analysis of wild ruminant tissues: Evolutionary implications for reducing diet-related chronic disease. Eur J Clin Nutr, 2002; 56:181-191.) she would know that our conclusions are based upon hundreds of hours of painstaking analysis. I don’t believe Fallon has ever analyzed the tissues of any wild animals - we have, and our scientific results are much different than her opinions.

Here’s another completely false statement: "And obviously he didn’t check up on canola oil, which he recommends as a source of omega-3 fatty acids—because virtually all canola oil is deodorized, a process that gets rid of the omega-3s." This statement shows how anyone can say anything on the internet with absolutely no systems of checks and balances that are normally provided by the peer review process in scientific publications. Any reader who wants to can access Medline (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi) and find numerous studies showing that canola oil contains about 10% of it’s total fatty acids as omega 3 fatty acids. Here are 2 citations (Dupont J et al. J Am Coll Nutr 1989;8:360-75; Ayorinde FO et al. Rapid Commun Mass Spectrom. 2000;14:608-15).

In regard to salt, Fallon again does the reader a disservice by not adequately presenting the data. The systematic mining, manufacture and transportation of salt have their origin in the Neolithic. Dragging and gathering salt from dry lakebeds is known to have taken place on Lake Yuncheng in the Northern Province of Shanxi, China by 6000 B.C. The earliest evidence for salt exploitation in Europe comes from salt mines at Cardona, Spain dating to 4200 - 3600  B.C. It is likely that Paleolithic or Holocene hunter-gatherers living in coastal areas may have dipped food in seawater or used dried seawater salt in a manner similar to nearly all Polynesian societies at the time of European contact   However, the inland living Maori of New Zealand lost the salt habit, and most recently studied inland hunter-gatherers add no or little salt to their food on a daily basis. Further, there is no evidence that Paleolithic (2.5 million years ago until 10,000 years ago) people undertook salt extraction or took interest in inland salt deposits. Collectively, this evidence suggests that the high salt consumption (~10 g per day) in western societies has minimal or no evolutionary precedent in all hominin species prior to the Neolithic period.

Fallon’s final paragraph represents opinion unsubstantiated by factual data. Again, if she would have taken the time to read our paper (Cordain L, Watkins BA, Florant GL, Kehler M, Rogers L, Li Y. Fatty acid analysis of wild ruminant tissues: Evolutionary implications for reducing diet-related chronic disease. Eur J Clin Nutr, 2002; 56:181-191.), she would have known that a modern Paleo Diet contains almost 8 times the RDA for vitamin A. Consequently, her statement that high protein diets lead to vitamin A deficiency is nonsense and completely untrue. Although hunter-gatherers did not consume dairy products, their bones were robust and resistant to fracture and rarely exhibited signs and symptoms of osteoporosis which is endemic in western populations. As we have outlined at my website as well as in the JANA paper and elsewhere, these people maintained strong bones because they were in calcium balance - meaning that calcium intake exceeded calcium losses in the urine. When the diet is net alkaline-producing, calcium balance can be maintained at lower calcium intakes.

Our recommendation to rub flax oil on meat prior to cooking was based on information published by the Flax Council showing that no oxidation occurred to flaxseed when cooked at 662 F for 60 min. Apparently, flax oil may respond differently than flaxseed for unknown reasons. Because of the new information we have rescinded our previous recommendation and suggest that flax oil be added after cooking (see website--click here for more information).

Fallon wraps up her diatribe by saying that we indicated diet sodas were part of hunter-gatherer diets. This statement is a ludicrous attempt to discredit our scientific work and the work of hundreds of dedicated scientists throughout the world who realize the value of evolutionary nutrition in treating multiple diseases of civilization. The most powerful and pervasive idea in all of biology is evolution through natural selection. It has only been in the last decade that this organizing template has been applied to nutrition and health. Great strides are now being made in understanding how clinically demonstrated principles underlying proper nutrition can be traced to our genome. Our genome was conditioned and shaped by environmental selective pressures that occurred long before the Agricultural Revolution. Since the appearance of our genus Homo, more than 2 million years ago, there have been at least 100,000 generations. Since the Agricultural Revolution of 10,000 years ago there have been only 500 human generations. Our genome simply has had insufficient time to adapt to the foods ushered in during the Neolithic (fatty meats, dairy products, whole grains and salty foods).

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