Nature's Bounty: The Way We Were

Picture a daily diet of fish and shellfish; of meats including fatty bone marrow and tongue; of fruits and vegetables, roots, nuts, and berries. Over the course of a year, you might eat 100 different types of fruits and vegetables. But you wouldn't drink any milk or consume any dairy products. Grains or cereal products would be unknown.

Because your carbohydrates would derive primarily from fruits and vegetables, you might take in a whopping 100 grams of fiber a day. Your diet would be rich in vitamins and minerals, as well as phytonutrients, since the wild plants and game sustaining you contain many micronutrients. Your food would supply minimal sodium but ample potassium, a mineral balance that would keep your heart beating regularly despite the lion lurking nearby.

As food plans go, it is—quite literally—catch-as-catch-can. This was the food available to our pre-agricultural ancestors of the Stone Age, hunter-gatherers all, who inhabited the earth from, say, 2 ½ million to 10,000 years ago.

The free-roaming deer and bison our Paleolithic parents killed provided more protein than you likely eat, but our ancestors hardly confined themselves to the lean muscle mass we favor. They preferred the rich organs, marrow, and brain, consuming a diet that not only had more fat but also quite different types of it than ours.

Because the animals were wild and not domesticated, they carried very little in the way of fat deposits, and very little of it was saturated. Much of it was made up of unsaturated omega-3 fatty acids, notably DHA, essential to human function and especially critical for the brain. Omega-3s are necessary to support the wiring of the nervous system, and are crucial to learning, memory, and maintenance of cell membrane integrity. They contribute to optimal operation of neurotransmitters and play a role in mood and behavior.

The amount and distribution of nutrients our forebears ate is a far cry from what most of us eat today. Overall, we consume fewer calories, but vastly different ones. Most contemporary carbohydrates come from grains, whose components can rob vitamins and minerals from the gut. Fewer than 10 percent of today's population consumes even the recommended 5 daily servings of fruits and vegetables.

The advent of agriculture brought the domestication of animals, and that has dramatically changed the composition of protein and fat in our diet. Today most animals are raised industrially, restricted in movement, fed and fattened on grain. In addition to altering the proportion of saturated fats and the amount of omega-3 fats in meat, grain feed has the effect of down-shifting the balance of omega-3 fats relative to omega-6s, a factor that greatly affects their biological availability. The Paleolithic diet tilted toward a 1:1 to 1:4 ratio of omega-6s to omega-3s, versus 11:1 today.

Increasingly, scientists believe that our bodies are metabolically adapted to what our Stone Age ancestors ate. Our genetic makeup has scarcely changed. "Nearly all the genes and epigenetic regulatory mechanisms we carry today were selected for behaviorally modern humans who appeared in Africa between 100,000 and 50,000 years ago," explains S. Boyd Eaton, an anthropologist at Emory University.

In an editorial in the American Journal of Clinical Nutrition, he and colleagues contend that we should be looking to the diet and activity patterns of Paleolithic humans as guides to a healthy life. The dietary and lifestyle differences between then and now account for most of our chronic diseases and cancer. In our quest to find cures to our modern plagues, moving forward requires looking backward.

Our Paleolithic parents consumed nary a granola bar or baked bean. And while some of our genes have changed, our core biological machinery has not. The human genome has changed only about 5 percent in the last million years.

The refined carbohydrates and processed foods, vegetable oils, and added sugars of our modern munchies yield a high glycemic load that raises levels of blood sugar and burdens insulin production, which, among other effects, promotes inflammation and atherosclerosis. We're still adapted to eat like hunter-gatherers.

Early humans consumed around 3,000 calories a day during periods of abundance. But physical activity—the equivalent of a 12-mile walk—kept weight at subsistence levels. Today, with our abundant and highly processed food supply, its ready availability, and the minimal energy expenditure required to access it, most people are given to consuming excess calories and storing them as unwanted body fat.

Other dietary differences include the acid-base balance of the body, the pH level of body fluids. Too much on the alkaline or acidic side and life itself is threatened. The ancestral diet provided an acid-base balance close to 1:1, but not our Neolithic diet. Both grains and dairy foods are acid-producing, causing the body to leach calcium from bones, jeopardizing bone and muscle health and leading to osteoporosis. The high net acid load we all carry is also a risk factor for kidney stones and high blood pressure.

Maybe in another 500,000 years, when our genes have finally caught up, we'll be able to tolerate the diet we now consume or even a more Earth-friendly, grain-based, vegan-type diet. But by then, we'll probably be able to eat plastic, too. —Leyla Muedin

Paleo-Prime Your Diet

There was no one Paleo diet. Our ancestors made the most of the environment wherever they were. It's possible to turn today's food supply into yesterday's finest fare.

• Try to get a little more than half your calories from lean meats (trimmed of all visible fat), organ meats, fish, shellfish, and poultry.
• Eat animal food at almost every meal. But that's not all you should eat.
• Consume unlimited amounts of fresh fruits and vegetables at every meal.
• Eliminate all dairy and grain products; they are poor sources of fiber, minerals and even B vitamins compared to other components of a Paleolithic diet.
• Avoid starchy vegetables such as potatoes in any form, including sweet potatoes.
• Put the salt shaker away; a squeeze of lemon can provide added taste.
• Add healthful vegetable oils: Olive, walnut, avocado, flaxseed, and canola are best.

Adapted from The Paleo Diet by Loren Cordain, Ph.D.