Paleolithic Diets

Paleolithic Diets


ROBERT CRAYHON: I'm very happy to be interviewing in this issue of total health, nutrition expert Dr. Lore Dr. Cordain is a professor at Colorado State University in Ft. Collins and has published countless papers in major scientific journals. He is an expert in the area of Paleolithic nutrition and human nutrition. Paleolithic nutrition, also known as Stone Age nutrition, examines what humans ate for 2.6 million years before the advent of agriculture. For that great expanse of time, humans were hunter-gatherers and only in the past 10,000 years have they been farmers. The dietary implications of spending the vast majority of history as hunters, not farmers, are far reaching.

Crayhon: Dr. Cordain, the United States Department of Agriculture (USDA) has given America the food guide pyramid. This pyramid tells us that a healthy diet is one that is predominantly carbohydrate, low in fat and protein. Is this grain-based, high carbohydrate diet truly ideal for humans

Dr. Cordain: There is increasing evidence to indicate that the type recommended in the USDA's food pyramid is discordant with the type of diet humans evolved with over eons of evolutionary experience.

Additionally, it is increasingly being recognized that the "food pyramid" may have a number of serious nutritional omissions. For instance, it does not specify which types of fats should be consumed. The western diet is overburdened not only by saturated fats, but there is an imbalance in the type of polyunsaturated fats we eat. We consume too many omega-6 fats and not enough omega-3 fats. The omega-6/omega-3 ratio in western diets averages about 12:1, whereas data from our recent publication( n1) suggests that for most of humanity's existence, prior to agriculture, the omega-6/omega-3 ratio would have ranged from 1:1 to 3:1.

High dietary omega-6/omega-3 ratios are associated with increased risk for cardiovascular disease, some types of cancer and tend to exacerbate many inflammatory diseases' responses.

Crayhon: What about the high carbohydrate die the pyramid recommends?

Dr. Cordian: The USDA food pyramid places breads, cereals, rice and pasta at its base and recommends that we consume 6-11 servings of these items daily. Nutritionists at the Harvard School of Public Health( n2) have recently publicly criticized this recommendation because it fails to distinguish between refined and complex carbohydrates and their relative glycemic responses. Dr. Walter Willett further pointed out that there was little empirical evidence to support the dominant nutritional message that diets high in complex carbohydrate promote good health.
Crayhon: Did our Stone Age ancestors ever eat cereal grains?

Dr. Cordain: Both the fossil record and ethnological studies of hunter-gatherers (the closest surrogates we have to Stone Age humans) indicate that humans rarely if ever ate cereal grains nor did they eat diets high in carbohydrate. Because cereal grains are virtually indigestible by the human gastrointestinal tract without milling (grinding) and cooking, the appearance of grinding stones in the fossil record generally heralds the inclusion of grains in the diet. The first appearance of milling stones was in the Middle East roughly 10-15,000 years ago. These early milling stones were likely used to grind wild wheat which grew naturally in certain areas of the Middle East. Wheat was first domesticated in the Middle East about 10,000 years ago and slowly spread to Europe by about 5,000 years ago. Rice was domesticated approximately 7,000 years ago in southeast Asia, India and China, and maize (corn) was domesticated in Mexico and Central America roughly 7,000 years ago. Consequently, diets high in carbohydrate derived from cereal grains were not part of the human evolutionary experience until only quite recent times. Because the human genome has changed relatively little in the past 40,000 years since the appearance of behaviorally modern humans, our nutritional requirements remain almost identical to those requirements which were originally selected for Stone Age humans living before the advent of agriculture.

Crayhon: What happened to our health when we switched from a hunter-gatherer diet to a grain-based one?
Dr. Cordain: The fossil record indicates that early farmers, compared to their hunter-gatherer predecessors, had a characteristic reduction in stature, an increase in infant mortality, a reduction in life span, an increased incidence of infectious diseases, an increase in iron deficiency anemia, an increased incidence of osteomalacia (severely weakened bones), porotic hyperostosis (a sign of acute iron deficiency anemia) and other bone mineral disorders and an increase in the number of dental caries and enamel defects. Early agriculture did not bring about increases in health, but rather the opposite. It has only been in the past hundred years or so with the advent of high tech, mechanized farming and animal husbandry that the trend has changed.

Crayhon: Did we move from a hunter-gatherer life style by choice or were we forced into the shift due to animal extinction?

Dr. Cordain: If we examine the fossil record, it suggests that a number of environmental pressures may have forced humans to adopt agriculture, including increases in human population densities and the depletion of easily hunted game. The extinction of large mammals all over Northern Europe, Asia, and North America coincide with the adoption of agriculture.

It is quite likely that pre-agricultural man had sufficient knowledge of his environment to know the life cycle of plants to be able to sow seeds and grow plants. However, ecologically it was not necessary nor energetically efficient to do so when human population numbers were low and game was plentiful Although agriculture is a vast science and encompass numerous disciplines, early agriculture essentially involved the domestication, growing and harvesting of cereal grains.
Crayhon: Is there enough evidence to suggest that a diet that includes a large amount of grains is a step down nutritionally, and one that is far from optimal for humans? And how much of the prehistoric diet was animal and vegetable?

Dr. Cordain: The fossil evidence as well as the ethnographic evidence from groups of hunter-gatherers studied in historical times suggests that the diet of pre-agricultural humans was derived primarily from animal-based foods. It is difficult quantitatively to determine from the fossil record the proportion of plant to animal food that was included in the diet of prehistoric humans. However, we do know that hunting of game was an important part of all pre-agricultural societies. Most prehistoric humans followed large game herds and manufactured tools and weapons which were regularly used to kill and butcher these animals. Ethnographic studies of living hunter-gatherer societies represent the best surrogate we have for estimating quantitatively the plant-to-animal subsistence ratios of Stone Age humans. We have recently compiled ethnographic data from 181 societies, worldwide, of hunter-gatherers showing that the mean plant-to-animal subsistence ratio in terms of energy was 35 percent plant and 65 percent animal. Thus the fossil and ethnographic data suggests that humans evolved on a diet that was primarily animal-based and consequently low-to-moderate in carbohydrate, high in protein and low-to-moderate in fat. This is in contrast to the lowfat, high-carbohydrate, plant-based diet which is almost universally recommended by modern day nutritionists. Clearly, humans can adapt to many types of diets involving multiple macronutrient combinations with varying amounts of fat, protein and carbohydrate. However, our genetic constitutions, including our nutritional requirements, were established in the remote past over eons of evolutionary experience. Human health and well being can be optimized when we use the evolutionary paradigm as the starting point for presents-day nutrition. Obviously, humans have had little evolutionary experience with the modern high-carbohydrate, high-fat, cereal based-diet which is omnipresent in western, industrialized countries. There is considerable evidence to suggest that these types of diets have the potential for creating health problems in some, but not all people.

Crayhon: How much cereal grains is too

Dr. Cordain: That varies with the person. Some people can handle more cereal grains than others. For a celiac patient a single teaspoonful of gluten containing grains is too much. Generally, health begins to be disrupted noticeably when cereal grains provide 70 percent or more of the daily caloric intake. The human dietary staple for more than two million years was lean game meat supplemented by fresh fruits and vegetables. Including lean meats (seafood, fish, game meat--if you can get it, lean cuts of poultry and domestic meat) more fruits, vegetables at the expense of cereal grains is a good starting point for improving nutrition.

Crayhon: How does one know if s/he can tolerate cereal grains? How does one know which ones suit them best?
Dr. Cordain: I suspect that for most people, a simple subjective test can be conducted in which they reduce the amount of cereal grains in their diet and replace the grains with more fresh fruits, vegetables and lean meats and seafood. I do know that all human beings don't do very well when total caloric intake of cereal grains approaches 70 percent. The high phytate content of whole grain cereals can impair mineral metabolism, i.e., iron, calcium and other anti-nutrients have the potential to interact with the gastrointestinal tract and perhaps the immune system as well as. The high lectin content of whole grain cereals can bind enterocytes in the small intestine and cause villous atrophy in addition o changing tight junction characteristics, thereby allowing intestinal antigens (both dietary and pathogenic) access to the peripheral circulation.

Crayhon: There seem to be many drawbacks to consuming grains in high amounts.

Dr. Cordain: Whole grain cereals are devoid of vitamin c and beta carotene (except for yellow maize). They have poorly absorbable vitamin B-6, and the phytate levels in grains impair the absorption of most of the divalent minerals. Additionally, they contain low levels of essential fats and have quite high omega-6/omega-3 fatty acid ratios. Excessive consumption of cereal grains is associated with a wide variety of health problems. In animal models, rickets are routinely induced by feeding them high levels of cereal grains. Hypogonadal dwarfism is found more often in populations consuming high amounts (~50 percent of total energy) from unleavened whole grain breads (i.e., in Iran where they consume an unleavened bread called tanok). . .

Crayhon: . . . and where there is widespread zinc deficiency.

Dr. Cordian: It is thought that the high levels of phytate in unleavened whole grain breads cause a zinc deficiency which in turn is responsible hypogonadal dwarfism, along with problems associated with zinc deficiencies. In Europe, where immigrants consume high levels of unleavened whole grain breads, rickets among their children remains a problem.
Crayhon: Are there particular grains that are more of a problem than others?

Dr. Cordain. Wheat, rye, barley and perhaps oats are problematical for individuals with celiac disease. Wheat seems to be associated with many autoimmune diseases. Ironically, whole grain cereals (which are thought to be more healthful than refined cereals because of their greater nutrient and fiber content) have more potential to disrupt mineral metabolism because of their higher phytate and antinutrient content. Although whole grain cereals intrinsically contain higher nutrient levels than do refined cereal grains, the biological availability of nutrients in whole grain cereals remains paradoxically low because of their high anti-nutrient content.

On the plus side, whole grain cereals, because of their high fiber content, tend to have higher glycemic indices than do their refined counterparts. Obviously, low to moderate amounts of cereal grains in the diet present little or no health problems to most people. The majority of the grain products consumed in this country are refined consequently many of the anti-nutrients are milled out.

Crayhon: Such as the bran?

Dr. Cordian: Yes, exactly. There's a trade-off. Milling takes out the but it also lowers the levels of vitamins and minerals.
Crayhon. Some assert that too much even beyond 60-70 grams per day, is bad for people, will damage the kidneys, liver and cause bone loss. Yet we find groups of people around the world who eat a pound or more of meat per day and don't seem to have any of these problems. What does your research suggest?

Dr. Cordain: Epidemiological studies have suggested that increased animal protein intake is associated with higher rates of osteoporotic fracture and many metabolic trials have demonstrated increased urinary calcium losses with increased protein intake. However, in order to establish cause and effect firmly, and hence proof that a certain variable is responsible for a certain effect, scientists conduct intervention trials. To my knowledge intervention studies have not been able to show that a change from low/moderate to high protein intake increases the rate of kidney stones or bone loss in either humans or animals.

Stone Age diets clearly were characterized by extremely high protein intakes by modern standards, yet bone robusticity and density (determined from fossil Paleolithic humans) were greater than or equal to that of most modern humans, despite the total absence of dairy products in Stone Age diets. This seeming paradox (low calcium intake, high protein intake yet strong, dense bones) may probably be explained by multiple factors. Stone Age humans were more active than modern people and consequently the everyday work they did resulted in greater bone loading, which in turn can influence bone density. Further, they lived outside most of the day so their sunshine exposure and hence vitamin D status would likely have been superior to most modern people who work indoors and get little sunshine exposure.
Last, the critical dietary factor influencing bone metabolism and hence osteoporosis is not calcium intake, nor calcium excretion, but rather calcium balance. The acid base status of the total diet, rather than calcium intake or excretion, determines calcium balance.

Foods which cause a net acid excretion include meat, fish, cheeses and grains. Fruits and vegetable have a net alkaline value and consequently reduce acid excretion. This reduces calcium loss, thereby halting bone resorption and actually allowing bone accretion to occur. Although the dietary calcium-to-protein ratio in Stone Age diets would have been quite low, the large amount of fruits and vegetables (35 percent of total energy) included in the diet would have produced a net dietary acid-base status which would have favored bone accretion even in the face of enormous protein intakes.
Crayhon: Most importantly, we thrived and were very healthy on this high protein, high meat diet.

Dr. Cordain: The fossil record and modern day studies of hunter-gatherers suggests this. Many populations around the world consume low fat, high carbohydrate diets with little or no animal protein, yet paradoxically suffer high rates of diseases of insulin resistance and high levels of cardiovascular disease. For example, epidemiological studies of largely vegetarian Hindu populations from the Indian sub-continent have shown mortality rates from cardiovascular disease that are similar or greater than those rates found in European countries, despite their vegetarian diet.
Crayhon: And that is apparently due to the imbalance in their macronutrients?

Dr. Cordain: Yes, these populations tend to have very characteristic blood lipid parameters indicative of syndrome X, a syndrome marked by elevated triglycerides, VLDL cholesterol and low HDL cholesterol. Also, the oxidative profile of their lipids tends to be worse than the oxidative profile of some western populations because cereal grains which have no vitamin C or no pro-vitamin A betacarotene may sometimes displace fruits and vegetables which are a rich source of both of these antioxidants.

Crayhon: In other words, the cholesterol "goes bad" in their body and causes more plaque to build up because they are missing these protective nutrients like vitamin C and beta carotene.

Dr. Cordain. Yes. Further, cereal grains tend to have a high omega-6/omega-3 ratio because they are high in linoleic acid and low in linolenic. The oxidizability of the LDL molecule increases when it's loaded up with omega-6 fats like those found in grains.

Crayhon: This brings us to the enormous topic of the shift in the kinds of fats we are eating: too many omega-Cs, like those found in safflower, sunflower, corn oil, and not enough omega-3 rich flaxseed oil, EPA/DHA and cold water fish. What has happened because of that shift?

Dr. Cordain: The types of fats that we eat influence the types of fats that are incorporated in the cell membrane. They can also influence hormonal profiles and eicosanoid function. We tend to see a more inflammatory profile with elevated levels of omega-6 fats.

Crayhon: How much omega-3 to omega-6 we should have in our diet?

Dr. Cordain: In our laboratory we have analyzed various tissues in wild game meat and we have found that muscle tissue contains and omega-6 to omega-3 ratio of 3.5-4 to 1. This ratio is higher in storage fat and bone marrow and slightly lower in certain organs. In the brain this ratio is 1 to 1. Pre-agricultural humans, as opposed to modern humans, enjoyed eating the organs of wild animals. Certainly, they were eating the brains of the animals that they killed. The omega-6 to omega-3 ratio couldn't have been much lower than 4 to 1 if we only ate the meat. If we ate only the brain, it would have been roughly 1 to 1. If fish were included in the diet, it would have further reduced the 4 ratio found in the muscle of terrestrial animals. Additionally, the inclusion of most plant foods (but not all) would have also reduced the 4 to 1 ratio. The conclusion I have come to is that the average omega-6/omega-3 ratio in pre-agricultural humans would have always been lower than 4 to 1, but probably not lower than 2 to 1 depending upon season, locale and macronutrient intake.

Crayhon: Looking at the food guide pyramid now with the Paleolithic perspective that you've helped create, what would you do if you were to design an eating guide for humans as a species?

Dr. Cordain: The evolutionary paradigm should be used as a starting point for design optimal nutrition guides. Clearly, it is not practical nor economically possible for all of the world's people to eat wild game, fruits and vegetables. However, the macronutrient and trace nutrient levels that typically occur in reconstructed Stone Age diets should be emulated in the design of healthful diets for modern people. Humanity is totally dependent upon cereal grains for survival. Cereal grains provide 56 percent of the food energy and 50 percent of the protein consumed by all of the world's peoples. Without them, there would be worldwide starvation of unprecedented proportions. We have wandered down a path of absolute dependence upon cereal grains, a path from which there is no return.

Crayhon: How many grain or carbohydrate servings should we eat per day, generally speaking?

Dr. Cordain: I think that there is a significant amount of genetic variability among people which may influence how well they do on various types of diets. Insulin resistant individuals do not seem to do well on high carbohydrate diets, particularly if the carbohydrate has a high glycemic index. Generally, most people do quite well health-wise on 23 servings of grain products per day. Clearly, cereal grains and agriculture allowed for the dramatic worldwide human population expansion that has occurred in the past 10,000 years since the advent of agriculture.

I think what the USDA is trying to do with its Food Pyramid is to give general dietary guidelines that are beneficial for most people and which are economically feasible. I think my work is not necessarily practical for making recommendations to all of the world's people, but rather it points out how human diets may be improved from an evolutionary perspective.

Crayhon: If you could speak to the modern health care practitioner, nutritionist or physician and tell them the key things Paleolithic research has taught us, what might those be?

Dr. Cordain: Animal-based diets can be healthful if designed with macronutrient and trace nutrients that emulate those of our pre-agricultural ancestors. Low-fat, high-carbohydrate cereal and legume-based diets are not necessarily healthful. The implications of a Paleolithic diet are that humans tend to do quite well on high protein animal-based diets in many regards including vitamin, mineral and fatty acid profiles. The whole concept that animal-based foods are deleterious needs to be rectified. The idea that if a little bit of whole grain is good for you then a lot should be better, needs to be reconsidered.

Crayhon: Dr. Cordain, thank you for spending time with us today and sharing these groundbreaking ideas with us. Your work embodies Stravinsky's phrase that "a revolution means going back all the way around to where you started from."
Dr. Cordain: My pleasure, Robert.


(n1.) Eaton S.B., Eaton S.B. 3rd, Sinclair, A.J., Cordain, L., Mann N.J. Dietary intake of long-chain polyunsaturated fatty acids during the Paleolithic Period. World Rev Nutr Diet (1998). Vol. 83 pp. 12-23.
(n2.) Willett W.C. "The dietary pyramid: does the foundation need repair?" Am J Clin Nutr (1998) Vol. 68 pp. 218-9.
By Robert Crayhon, M.S., C.N.
Adapted by M.S., C.N.

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