The Paleo Diet: An Interview with Dr. Loren Cordain
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Introduction
>> Ten thousand years ago the Agricultural Revolution was the beginning of a drastic change in the human diet that continues to this day. Today more than 70% of our dietary calories come from foods that our Paleolithic ancestors rarely, if ever, ate. The result is epidemic levels of cardiovascular disease, cancer, diabetes, osteoporosis, arthritis, gastrointestinal disease, and more.
- Dr. Loren Cordain
Conventional notions of healthy eating were shaken with the publication of Dr. Loren Cordain's 2002 book, The Paleo Diet. In the midst of the low-fat, processed food health craze, this Colorado State University researcher argued that many of our modern notions of healthy foods were way off base. His persuasive arguments helped ignite the rejection of low-fat approaches popular in the 90s.
Dr. Cordain examined eating habits of hundreds of primitive hunter-gatherer cultures constructed from archeological remains, as well as studies of primitive cultures in existence today but isolated from modern society. His studies have brought to light how far the modern diet has strayed from foods that humans evolved to eat.
Imagine a Paleolithic human confronted with a Twinkie or even a pizza. He or she wouldn't even recognize these modern-day treats as food.
- Dr. Loren Cordain, The Paleo Diet
No stranger to controversy, Dr. Cordain's critics have often cited the brief lifespan of primitive cultures as the reason for lack of more chronic diseases like heart disease, diabetes, and cancer. But, always a scientist, Dr. Cordain has supported his assertions with hard findings from his studies. Although lifespan among primitive cultures are shortened by traumatic injury and infections, the substantial proportion of survivors in their 5th and 6th decades are uniformly free of chronic diseases. And, irrespective of lifespan, Dr. Cordain argues that the practice of grain farming that marked the beginning of the Agricultural Revolution somewhere around 8000 B.C. also coincided with a substantial upsurge in chronic diseases.
There is growing awareness that the profound changes in the environment (e..g, in diet and other lifestyle conditions) that began with the introduction of agriculture and animal husbandry 10,000 years ago occurred too recently on an evolutionary time scale for the human genome to adjust. In conjunction with this discordance between our ancient, genetically determined biology and the nutritional, cultural, and activity patterns of contemporary Western populations, many of the so-called diseases of civilization have emerged. In particular, food staples and food-processing procedures introduced during the Neolithic and Industrial Periods have fundamentally altered 7 crucial nutritional characteristics of ancestral hominin diets: 1) glycemic load, 2) fatty acid composition, 3) macronutrient composition, 4) micronutrient density, 5) acid-base balance, 6) sodium-potassium ratio, and 7) fiber content. The evolutionary collision of our ancient genome with the nutritional qualities of recently introduced foods may underlie many of the chronic diseases of Western civilization.
Loren Cordain et al.
Origins and evolution of the western diet:
Health implications for the 21st century.
Am J Clin Nutr 2005
Dr. Cordain advocates a return to the eating habits of our ancestors. Fresh fruits, vegetables, lean meats, and seafood form the core of this approach. Conspicuously absent are wheat and dairy products, as Dr. Cordain argues that a surge in heart disease and diabetes developed when these two food groups were adopted into the human diet.
Does Dr. Cordain advocate hunting for your own wild game? Of course not, but he does advocate re-creating the nutrient composition of diets of primitive cultures.
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.
- Dr. Loren Cordain, The Paleo Diet
What does this have to do with coronary plaque-control? As Cordain points out, the nutrient-rich, high-fiber, low glycemic index/low sugar, and high mono-unsaturated fat content of the Paleo Diet approach fits well with the Track Your Plaque philosophy. Although we're not as strict on curtailing grains and dairy products, perhaps Dr. Cordain has something to teach us.
Interview
TYP: Primitive cultures rely a great deal on captured game for food and the Paleo Diet advocates including plentiful lean meats in your diet. Doesn't a meat-based diet like our Stone Age ancestors promote high blood cholesterol and heart disease?
Dr. Cordain: 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 U.S. A 100-gram serving of roast [free-range] buffalo contains only 2.4 grams of fat, and 0.9 g of saturated fat, whereas a 100-gram, T-bone [grain-fed] 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.
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 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 [artery wall lining tissue] 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. 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.
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
TYP: To what extent do you think the level of small-dense LDL cholesterol explains the "badness" of LDL? This is relevant to The Paleo Diet because small-dense LDL is strongly correlated with triglycerides. On The Paleo Diet, the result is often somewhat elevated LDL, but reduced triglycerides. Low triglycerides signals low levels of small-dense particles in the LDL fraction.
Dr. Cordain: 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.
TYP: Why do you recommend eating lean meats? Wouldn't hunter-gatherers have savored fatty meats?
Dr. Cordain: 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 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 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 21st 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.
TYP: The Paleo Diet approach advocates dramatically reducing or eliminating grains from the diet. Aren't whole grains good sources of fiber, minerals, and B vitamins?
Dr. Cordain: 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.
TYP: What direction is your research taking you?
Dr. Cordain: Currently, our group is studying meal patterns in hunter gatherer societies and how they impact health and well being. In the western world, we typically eat 3 meals a day and snacks. Hence, day-long grazing typifies western meal patterns. In hunter-gatherer societies, the most consistent eating pattern is a single large meal in the late afternoon or evening. A midday meal or lunch is rarely or never consumed. Breakfast is infrequently eaten and when it is taken, typically consists of the previous evening meal leftovers. During gathering, snacking sometimes takes place, but most consistently the bulk of the daily calories are taken at one single meal at the end of the day. This meal pattern can be labeled intermittent fasting, and our work and others (Mark Mattson, in particular) show it to have beneficial health effects when compared to many smaller meals throughout the day.
About Dr. Cordain
Dr. Cordain received his Ph.D. in Health from the University of Utah in 1981 and has been employed as a Professor in the Department of Health and Exercise Science at Colorado State University since 1982. He is married and has three sons.
Featured on Dateline NBC, the front page of the Wall Street journal, and the New York Times, Loren Cordain is widely acknowledged as one of the world's leading experts on the natural human diet of our Stone Age ancestors. He is the author of more than 100 peer-reviewed scientific articles and abstracts. His research into the health benefits of Stone Age Diets for contemporary people has appeared in the world's top scientific journals including the American Journal of Clinical Nutrition, the British Journal of Nutrition, and the European Journal of Clinical Nutrition among others. Dr. Cordain's popular book, The Paleo Diet, has been widely acclaimed in both the scientific and lay communities. His newest offering, The Paleo Diet for Athletes, is slated for publication in November 2005. He is the recent recipient of the Scholarly Excellence award at Colorado State University for his contributions into understanding optimal human nutrition.
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