By Loren Cordain, Ph.D.

The scientific community almost unanimously agrees that the diseases and disorders that plague Western civilization - obesity, cardiovascular disease, and Type II diabetes - are related to our diets ... and that they are avoidable. But nutritional experts are in complete disagreement over which type of diet is best for prevention and treatment.

The U.S. government recommends between 6 and 11 servings of cereal grains daily, 2 to 3 servings of dairy foods, and the limited consumption of fats and sweets.

Other nutritional authorities, such as Dr. Dean Ornish, encourage us to lower dietary fat to less than 10 percent of calories and to eat plenty of whole grains and legumes. Noted alternative health physician Dr. Andrew Weil agrees with Ornish's advice on whole grains and legumes, but takes issue with his fat recommendation, saying it is too low and deficient in omega-3 fatty acids (the kind found in fatty fish like salmon).

Still other nutrition gurus, such as Dr. Neal Barnard, president of the private non-profit Physicians Committee for Responsible Medicine, caution us to eliminate all animal products from our diets, including meat, eggs, dairy, and fish. In stark contrast, Dr. Atkins told us to reduce our carbohydrate content to less than 100 grams a day and to eat all the fatty, salty meats and cheeses we desire.

Is there any way to make sense of all this? What is the optimal diet for improving health, losing weight, and reducing the risk of chronic illness?

The answer can be found by looking at the way our hunter-gatherer ancestors ate. These same foods - or their modern-day equivalents - are the ones that should serve as a starting point for our optimal nutrition.

Stone-Agers Living in the Space Age

Although we live in a world of vast cities and complex technologies, each of us has a Stone Age genetic makeup. DNA studies from diverse ethnic groups around the world confirm that the present-day human genome is virtually identical to that of humans living 40,000 years ago.

Beginning some 10,000 years ago, people left behind the hunting and gathering way of life and began to sow and harvest the genetic forerunners of today's wheat and barley. Shortly thereafter, these early farmers domesticated farm animals. Five thousand years later, the so-called Agricultural Revolution had spread from the Middle East to Northern Europe and beyond.

But there has been very little time, evolutionarily speaking, for our bodies to adapt to this new way of eating. Although 10,000 years sounds historically remote, it is evolutionarily quite recent. Only 500 human generations have come and gone since agriculture began.

Cheeseburgers vs. Barbecued Buffalo

Cereal grains currently provide 50 percent of the protein consumed on this planet. Yet wild versions of this modern-day staple were rarely, if ever, consumed by hunter-gatherers. Dairy products weren't part of humankind's original fare, either. (It's pretty difficult to catch a wild mammal, let alone milk one.) And except for rare treats of honey, refined sugars weren't on the Stone Age menu. Nor were fatty meats, salt, yeast-containing foods, or legumes.

Obviously, the highly processed foods that now dominate the American diet weren't part of the Paleolithic (Old Stone Age) meal plan. Hunter-gatherers probably wouldn't have recognized pizza, chips, French fries, ice cream, soda, and the like as food at all.

Lean game and fish were their staple foods. Consequently, the Paleolithic diet was much higher in protein than the typical U.S. diet. Because game is so lean on a calorie-by-calorie basis, it contains about 2.5 times as much protein per serving as domestic meats. For instance, a 100-calorie serving of America's favorite meat - hamburger - contains a paltry 7.8 grams of protein. Compare that with 19.9 grams in an identical 100-calorie serving of roasted buffalo. Game is also healthier. It contains two to three times more cholesterol-lowering polyunsaturated fats and almost five times more omega-3 fatty acids than meat from grain-fed domestic livestock.

The carbohydrate content in the average hunter-gatherer diet was extremely low. More important, it was made up almost entirely of wild fruits and vegetables. Their total fat content was similar to or slightly higher than current U.S. figures, and consisted of healthful, cholesterol-lowering monounsaturated fats, which comprised about 50 percent of total fats consumed. In contrast, the typical U.S. diet has less cholesterol-lowering mono- and polyunsaturated fats, more artery-clogging saturated fats and trans-fats, and seven to 10 times less heart-healthy omega-3 fatty acids than in hunter-gatherer diets.

The key to the optimal human diet lies in the evolutionary wisdom of our hunter-gatherer past. The best high-protein options are fish (particularly fatty northern fish such as salmon, halibut, mackerel, and herring), shellfish, grass-fed beef and pork, free-range chicken and turkey, rabbit, and any kind of game, either bought or hunted. (The gastronomically adventurous can find buffalo, ostrich, emu, kangaroo, and venison at many upscale supermarkets and health food stores.)

The Missing Link Between Diet and Disease

In the 1950s, when scientists were first unraveling the link between heart disease and diet, they found that saturated fat raised blood cholesterol levels and increased the risk for coronary heart disease. Dietary sources of saturated fat, such as fatty domestic meat, were deemed unhealthful, and rightly so. Unfortunately, the message the public and many nutrition professionals got was that all meat was unhealthful and promoted heart disease and cancer.

But it turns out that high amounts of animal protein are quite healthful for the human species. It's the saturated fat that can accompany protein that causes problems. The grains fed to many domesticated animals turn healthful lean protein with a proper balance of good fats into a nutritional nightmare that promotes disease.

Consumption of lean meat actually lowers blood cholesterol levels and thereby reduces the risk of coronary heart disease. Consumption of lean animal protein elevates HDL cholesterol (the "good" cholesterol) while reducing triglycerides, LDL cholesterol (the "bad" cholesterol), and total cholesterol. In contrast, low-fat, high-carbohydrate diets tend to elevate triglycerides and lower HDL cholesterol. High-carbohydrate diets also raise small dense LDL cholesterol - one of the most potent predictors for atherosclerosis and heart disease.

Studies have also indicated that elevated dietary protein reduces the risk of stroke and hypertension and helps boost survival time for women with breast cancer. And a high-protein diet improves or normalizes insulin metabolism in Type II diabetics. In other words, lean animal protein is good for us and saturated fat is not.

Putting It All Together

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 by evolution and natural selection. It is based upon extensive scientific research examining the types and quantities of foods our hunter-gatherer ancestors ate.

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 they are low in the nutrients (refined sugars and grains, saturated and trans-fats, salt, and high-glycemic carbohydrates) that frequently cause weight gain, cardiovascular disease, diabetes, and numerous other health problems.

You might consider it heretical to believe that lean meat is healthful while whole grains and dairy products are not necessarily so. But the basis for this conclusion comes from overwhelming evolutionary evidence that is increasingly being substantiated by human, animal, and tissue studies.

We all remain hunter-gatherers, displaced in time, yet still genetically adapted to a diet dominated by lean meats and fresh fruits and veggies.
[Ed. Note: Dr. Loren Cordain is on the faculty of the Department of Health and Exercise Science at Colorado State University. During the past two decades, he has researched the effects of diet on human health and has specifically examined links between modern diets and disease. He is the author of numerous scientific articles, and has published three popular books, The Paleo Diet, The Paleo Diet for Athletes, and The Dietary Cure for Acne.]