Hi Patrick,
Many thanks for your support of the Paleo Diet concept . Let me briefly answer your questions:
Q: presently I am reading Weston Price’s Nutrition and Physical Degeneration, and it has presented me with a conundrum regarding the hunter-gatherer diet and Dr. Price’s observations. As you may know, in the 1930s Price found several examples of very healthy isolated peoples who ate no processed foods, and consumed raw dairy and whole grain products as part of what might otherwise be considered a Paleolithic diet. Specifically, I’m talking about the numerous villages Price studied in both the Swiss Alpines and the Scottish Outer Hebredes islands.
A: Dr. Price observed the Swiss eating copious amounts of raw cheese (both goat and cow), raw butter, and raw milk as well as a significant amount of whole grain rye bread. Yet he noted that the villagers were in excellent health. In fact, he remarks that the people in certain villages were historically famous throughout Europe for their superior constitution. He also found the Scots, who ate large quantities of oats along with seafood and fish organs, to be extremely robust. Do you believe Price’s observations to be merely anecdotal and therefore not worthy of scientific consideration? Or might some factor explain why certain traditional peoples were able to thrive on diets that included minimally processed products of agriculture? (Perhaps our genes allow for a certain amount of leeway when it comes to raw dairy and fresh, unrefined grains? Or, regarding milk, perhaps the hunger-gatherer societies did consume some milk of other species when they killed and ate pregnant animals?)
I believe the closer people can approach dietary characteristics that mimic our ancestral diet, the better the collective health of the population will be. In the 1920s and 30s, when Price made his observations of less westernized populations in parts of Europe, his comparison groups were Americans and Europeans living in urban areas who had increasingly begun to include refined sugars, refined grains, refined vegetable oils, processed and salted foods into their diets. Furthermore, urban populations had increasingly become sedentary by the 1930s, and cigarette smoking became common place. All of these dietary, exercise and behavioral habits were typically not part of the environmental factors that affected the health of rural farmers and fishermen in small villages and towns. Accordingly, it is not surprising that the collective group health of most rural Europeans in the 1930s many have been superior to their counterparts living a more urbanized life.
In regard to dairy and whole wheat. The incidence of celiac disease among Europeans is about 1 in 100, indicating from this single perspective that wheat was still problematic as a population. Recent research has shown that wheat consumption in healthy normals causes a leaky gut, which tends to promote chronic low level inflammation – a universal characteristic of heart disease, cancer and autoimmune disease. Because most people living in isolated rural villages in 1930s Europe had little or no access to community based hospitals or health clinics, there is scant epidemiological data reporting their collective health - particularly mortality rates from all causes. Hence, there is really no good way to be sure that Price’s anecdotal observations of single individuals were representative of the population. Price did not have the ability nor technology to measure lactose intolerance in these populations. Recent data supports the notion that from this perspective, perhaps 20-30% or more of these people couldn’t digest milk without gastric upset. Similar to wheat, this information supports the notion that Europeans were not fully adapted to either milk or wheat.
Q: as a side note, of the many "primitive" societies Price observed across the globe, he observed the Eskimos to be "an example of physical excellence and dental perfection such as has seldom been excelled." That’s not news to you, I’m sure, but it makes me chuckle when I think of how the many vegans in Boulder would react.
A: the down side to Price’s observations here is that he did not have DEXA machines to evaluate bone mineral density in these groups, and more recent data suggests that bone mineral health may have been compromised at an earlier age among the Inuit than in populations who had access to more plant food. Hence, although from cardiovascular, cancer and autoimmune perspectives, these people had superb health, other dimensions did not fare so well. I believe that a diet which includes about 35-45% plant food, along with 55-65% animal food, would prevent the bone mineral problems the Inuit may have experienced.
Q: My next question is a follow up of one I asked during your lecture, regarding the percentage of raw foods eaten by hunters and gatherers. I believe you thought I was asking about the validity of a vegetarian diet, but my question was really this: Since the Paleo Diet is an attempt to mimic what our evolutionary ancestors ate, is not the percentage of cooked versus raw foods eaten by Stone Age people pertinent information? E.g., if our ancestors ate most of their vegetables raw, should we perhaps be doing the same? I took from your remarks on Saturday that you do not think that raw versus cooked is a major issue, but nevertheless do you know of any investigations into the percentage of raw foods eaten by Paleolithic people and/or more recent hunter-gather societies?
A: the Paleolithic period spans from the first continual appearance of stone tools in the fossil record ~2.6 million years ago until the beginning of the agricultural revolution ~10,000 years ago. Early hominids had little or no access to regular fires because they could not make it. Hence, all foods would have been consumed raw until fire was controlled. Although there is some scanty - and non-convincing - evidence that fire making may have occurred earlier, most data shows that it was rare until 250,000 to 300,000 years ago. After that time hearths begin to appear in the fossil record, suggesting that fire had been mastered.
In historically studied hunter-gatherers, the preferred method to start a fire is with the use of a fire stick or drill in which a long straight wooden dowel is rubbed between the two hands, so that the bottom of the stick rapidly rotates back and forth into a flat piece of wood with a pre-drilled indentation and a tiny notch. The friction created between the rotating dowel and the notched wood eventually creates tiny, hot charcoal embers which spill from the notches into tinder (dry grass, etc.) placed below. By blowing on the smoking charcoal in the tinder, a fire can be coaxed into being. However, this is no easy process - requiring patience, skill, perseverance and careful hand-eye coordination. Most trained anthropologists cannot start fires in this manner without considerable practice and training, and our closest living ancestor - the chimpanzee - has never produced fire via this procedure - even with human training and intervention. Hence the behavioral sophistication, creativity and motor skills required to control fire via this procedure likely came even later still after the first sporadic appearance of fire in the archaeological record 250,000 – 300,000 years ago. These very first fires - before the invention of fire drills - likely originated from fire collected after lightening strikes and kept alive for days or weeks after its initial collection.
Anatomically modern humans first appeared in the archaeological record about 200,000 years ago in Africa, so it seems likely that control of fire was a skill Homo sapiens may have mastered from the very origins of our species. Cooking makes many inedible plant foods edible by reducing the antinutrient load, gelatinizing starch granules, and breaking down plant cell walls. It also allows for consumption of frozen animal carcasses at far north latitudes. So, to answer your question, all food was consumed raw before the control of fire. As humans exploited all parts of the planet, fire was increasingly used to make non-edible plant foods edible. Hence, the long-term evolutionary norm was the consumption of only raw plant foods that could be digested and assimilated in their raw form without toxic effects. Animal foods can be digested and assimilated in both their raw and cooked forms despite recent evidence suggesting otherwise.
Do I recommend eating meat raw? No, for the reasons stated in my first book – it increases the risk for E. Coli and other bacterial and pathogen contamination. For plant foods, I suggest eating those plant foods raw which you typically enjoy raw (most fruits and some veggies). For veggies, light steaming can increase their palatability, and reduce vitamin and mineral loss. For plant foods which are either inedible or toxic in their raw state, I suggest not eating these at all. They are cereal grains, legumes, beans and potatoes.
Q: My next question is one that I am frequently asked when I tout the Paleo Diet to more conventional nutritionists. They claim that the diet is suited for humans who typically lived to only to about 30 years old, so there’s no knowing its effect in preventing degenerative diseases seen in people 40 years and older. There are a number of reasons why this argument seems weak to me, but I’m wondering how you typically handle it.
A: I have been asked this question so many times, that we actually wrote a scientific paper on the topic: Eaton SB, Cordain L. Evolutionary Health Promotion. A consideration of common counter-arguments. Prev Med 2002; 34:119-123, which you can download from my website:
http://www.thepaleodiet.com/published_research/.
Q: Also, which of your scientific papers would you recommend I start with to familiarize myself with the Paleo Diet argument more rigorously? (I have a B.S. in chemistry, and I'm comfortable with scientific reports.) And is there one study in particular that delineates the specific foods you believe Stone Age people to have eaten? I am about to start blogging for a local publisher of nutrition and health books, and I would like to be well informed about the diet since it seems to me it is only going to gain more (well-deserved) attention as we move forward.
A: Here are some of the classic papers which really get into the Paleo Diet concept, and which I would recommend to all of our readers. I list them in chronological order, from most recent. If you only have time to read three papers, I recommend that you read #2, # 11, and # 13.
1. Cordain L. Saturated fat consumption in ancestral human diets: implications for contemporary intakes. In: Phytochemicals, Nutrient-Gene Interactions, Meskin MS, Bidlack WR, Randolph RK (Eds.), CRC Press (Taylor & Francis Group), 2006, pp. 115-126.
2. Loren Cordain, S. Boyd Eaton, Anthony Sebastian, Neil Mann, Staffan Lindeberg, Bruce A. Watkins, James H. O’Keefe, Janette Brand Miller. Origins and evolution of the western diet: Health implications for the 21st century. Am J Clin Nutr 2005;81:341-54.
3. O'Keefe JH Jr, Cordain L. Cardiovascular disease resulting from a diet and lifestyle at odds with our Paleolithic genome: how to become a 21st-century hunter-gatherer. Mayo Clin Proc 2004 Jan;79(1):101-8.
4. Cordain L, Eades MR, Eades MD. Hyperinsulinemic diseases of civilization: more than just syndrome X. Comp Biochem Physiol Part A 2003;136:95-112.
5. Cordain L, Lindeberg S, Hurtado M, Hill K, Eaton SB, Brand-Miller J. Acne vulgaris: A disease of western civilization. Arch Dermatol 2002; 138:1584-90.
6. Cordain L, Eaton SB, Brand Miller J, Mann N, Hill K. The paradoxical nature of hunter-gatherer diets: Meat based, yet non-atherogenic. Eur J Clin Nutr 2002; 56 (suppl 1):S42-S52.
7. 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.
8. Cordain L, Eaton SB, Brand Miller J, Lindeberg S, Jensen C. An evolutionary analysis of the etiology and pathogenesis of juvenile-onset myopia. Acta Ophthalmologica Scandinavica, 2002; 80:125-135.
9. Cordain L. The nutritional characteristics of a contemporary diet based upon Paleolithic food groups. J Am Nutraceut Assoc 2002; 5:15-24.
10. Cordain L, Watkins BA, Mann NJ. Fatty acid composition and energy density of foods available to African hominids: evolutionary implications for human brain development. World Rev Nutr Diet 2001, 90:144-161.
11. 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.
12. Cordain L, Toohey L, Smith MJ, Hickey MS. Modulation of immune function by dietary lectins in rheumatoid arthritis. Brit J Nutr 2000, 83:207-217.
13. Cordain L. Cereal grains: humanity’s double edged sword. World Rev Nutr Diet 1999; 84:19-73.
14. Cordain, L., Gotshall, R.W. and Eaton, S.B. Physical activity, energy expenditure and fitness: an evolutionary perspective. International Journal of Sports Medicine 1998; 19:328-335.
Cordially,
Loren Cordain, Ph.D., Professor
