Science / Medicine : Genes From Stone Age Make Us Crave Those Fat, Unhealthy Foods
Consider an apple, ripe and juicy.
Cut a slice, bring it close and take a bite.
As the complex sugar molecules in the apple’s juices flood over your palate, some of them lock onto special receptor cells at the back of your tongue. The receptors fire their messages along nerve pathways to your brain, generating sensations of pleasure, along with a flow of saliva into your mouth. Thus stimulated, you take another bite . . . and answer an imperative many thousands of years in the making.
Such sensations told your Stone Age ancestors, “This food and your body are made for each other.”
Evolution matched early man to the available diet, causing him to take pleasure in foods, such as ripe fruit, that served his body well; scarcity led him to adapt to a variety of plant and animal foods available on the African savannah 100,000 years ago.
And there, in the Stone Age, says Atlanta radiologist S. Boyd Eaton, lie the roots of the modern diet, good and evil.
“We see ourselves as 20th-Century people,” Eaton says, “but our genes are still from the Stone Age--displaced through 100,000 years to a hostile environment. Our minds are comfortable living in the present, but our biology and physiology are holdovers from the remote past, even before agriculture, when our ancestors lived as hunter-gatherers.”
‘Three Kinds of Foods’
Thinking about the very different lives of our culturally remote ancestors led Eaton to an obvious question: What are we genetically programmed to consume?
In answering that question, Eaton also came up with a plausible answer to another question many of us have asked ourselves: Why do we seek out the very foods that are least healthy for us?
“I think we have cravings for three kinds of foods,” Eaton explains.
- We crave sugar because our ancestors subsisted on ripe fruit.
- We crave sodium because we evolved in a climate in which salt was very difficult to find. There is very little sodium in plants, and not much in wild animal protein. This may be why the mammalian kidney has a well-developed mechanism to conserve sodium.
- We crave fat because some fat is essential for health, yet fat was very difficult to get from game animals in Africa, where humans evolved.
In sum, we hoard certain substances as though we had grown up in a dietetic Depression. Only this was an ancestral Depression, and it lasted almost 100,000 years.
There have been no big changes in our genes or physiology since anatomically modern humans arose in Africa. So studying the habits of early humans can tell us something about how we are designed to live.
Of course, no true Stone Age people exist today. So Eaton has obtained evidence from two indirect sources: fossil remains of Stone Age peoples and the study of primitive hunter-gatherer tribes that still roam parts of Africa.
Only 20% Fat
Eaton’s study of contemporary hunter-gatherers was enhanced by a chance meeting with the husband-and-wife anthropologist team of Melvin Konner and Marjorie Shostak. The anthropologists had spent several years studying at firsthand one of the few surviving hunter-gatherer tribes, the !Kung people of the Kalahari Desert.
Now the three have pooled their observations in a book titled “The Paleolithic Prescription,” to be published in June. In addition to a discussion of Stone Age diet and exercise patterns, the book shows us what we can learn from Paleolithic tribes about social behavior, such as the role of women and treatment of children. Eaton has written more on this subject in an article to be included in the April issue of the American Journal of Medicine.
The composition of the Stone Age diet was quite different from that of ours. Based on comparisons with present-day hunter-gatherers, our ancestors appear to have obtained 20% of their calories from fat, 20% from protein, and 60% as complex carbohydrates. That’s a much higher intake of carbohydrates and much less fat than that of the average Westerner.
In addition, the carbohydrates in the Stone Age diet were complex compounds, not simple sugars, Eaton emphasizes. That’s quite a contrast with some modern American adults, who may get up to 10% of their calories as alcohol.
Because the Paleolithic diet consisted largely of wild plants, they took in much more fiber, too. Eaton has analyzed samples of about 150 wild plant foods of the type that hunter-gatherer tribes depend on. He concludes that they ingested between 100 and 150 grams of fiber per day. People living in Western societies take in less than 20 grams per day.
Modern humans also diverge from our ancestors in salt consumption. “We are the only mammalian life form that consumes more sodium than potassium,” Eaton says.
‘Screwed Up Red Meat’
Our prehistoric ancestors did eat a lot of red meat, more than the American Heart Assn. diet allows. We could eat more red meat, too, Eaton says, if we could catch wild game. The problem, in his view, is that “we humans have screwed up red meat.” First, we have bred cattle to put on fat quickly; second, we raise cattle very unnaturally, using fortified feeds with a high fat content.
For example, Paleolithic people ate a lot of venison. Deer got 80% of their calories from plant protein, and one-third of venison fat is polyunsaturated, the healthier kind of fat. Choice beefsteak, on the other hand, comes from cows who get 80% of their calories from fat. Only 7% of beef fat is polyunsaturated.
Necessary Exercise
And reconstructing the daily life of a hunter-gatherer tribe provides another vital piece of information--the optimal type and intensity of exercise for keeping healthy.
Eaton thinks of Paleolithic peoples as being like decathlon athletes, with a combination of aerobic capacity and muscular strength. This leads him to conclude that the optimal exercise prescription for health is a blend of resistance and aerobic training, which means some weight-lifting and some walking, running, swimming or bicycling.
No one can accuse Eaton of ignoring his own advice. On a typical day recently, his breakfast consisted of Familia with no added sugar, bananas, skim milk, orange juice, no-salt whole wheat bread, low-sugar preserves, and a spoonful of oat bran on the cereal. On other days he varies this with shredded wheat, dates, figs or raisins.
At lunch he was pressed for time, so he had only an apple, a banana and a cup of low-fat fruit yogurt (raspberry).
Nutritional Equivalency
For dinner the family ate lobster, sliced pears, peas and a dessert of yogurt. “The lobster is highly unusual,” he says. A more typical dinner entree would be chicken or fish, not cooked in a fatty sauce.
None of this is caveman fare. Eaton follows the principle of equivalency: He aims to eat the same nutritional content as prehistoric people, though not in the same packages.
For his exercise he walks to and from work each day, a total of 2 miles. He also does a daily one-hour workout, alternating between weightlifting and bicycling.
“With modern technology we can cram a lot of exercise into a short time,” Eaton says. “We must blend the best from the past with the best from the present.” Efficient exercise is a necessity with his 10- to 12-hour days at the hospital.
Despite their dietary and exercise patterns, the health status of Paleolithic people certainly wasn’t ideal. They had an average life expectancy of only about 35 years. Most died of trauma or infection (as did the majority of people in every civilization before the 19th Century). There is good skeletal evidence that they were often injured and had degenerative diseases, such as overuse injuries. In addition, their teeth were ground down from eating coarse food.
Afflictions of Affluence
But they did not have what Eaton calls the “afflictions of affluence,” particularly coronary heart disease. This was not just because they did not live long enough to develop these conditions. Proof comes from comparing autopsies of modern-day hunter-gatherer males who died young and Western males dying young.
Among a group of young Americans who died in the Korean War, 15% already had significant coronary artery disease. But autopsies done by a British doctor in Kenya on young Kikuyu tribesmen between 1927 and 1937 showed no significant coronary artery disease.
“The Paleolithic Prescription” is a title that Eaton admits will be puzzling to some people. Still, he has high hopes for the book and the ideas it espouses. He recalls another book with an enigmatic title that changed American life styles. “Twenty years ago when Dr. Kenneth Cooper wrote a book called ‘Aerobics,’ nobody knew what that meant,” Eaton points out. “Now it’s part of our everyday vocabulary.”
Report Comments on Nutrition in Animal Products
The nutritional value of animal products in the human diet will be the subject of a long-awaited National Research Council committee report to be issued Tuesday in Washington. The report, capping 2 1/2 years of work by the committee, will present the panel’s conclusions and recommendations on questions such as how animal products measure up against established dietary guidelines.
A ‘FATTER’ DIET FOR TODAY’S HUMANS Our Paleolithic ancestors appear to have had a diet with a much higher intake of carbohydrates and much less fat. In fact, the average American eats double the amount of fat than the Stone-Age man, which increases the risk for hormonal cancers, such as breast, prostate and uterine cancer.
Stone-Age Man’s Diet 60% complex carbohydrates 20% protein 20% fat
Modern American Diet 46% complex carbohydrates 12% protein 42% fat
