Can a looming diabetes epidemic be averted by a hunter-gatherer lifestyle?
I just got back from a conference at Harvard where I gave an after-dinner talk (at the Harvard Faculty Club, no less) on a subject guaranteed to give everyone indigestion: why our ancestors ate healthier than we do.
I described in words and photos the lives of the !Kung hunter-gatherers depicted at the top of this page, as I and others saw it during two years of field work between 1969 and 1975. I briefly discussed hunter-gatherer studies generally, and I talked about the implications of hunter-gatherer life for us today.
We call it the mismatch hypothesis: Since the human genome was formed during the 99 percent of human history when we were hunting and gathering for a living, then a drastic change in the environment without major genetic change could result in a mismatch.
So far, so good, but there are questions. First, does whatever feature of life you are attributing to hunter-gatherers really apply to most or all of them, not just one or a few cultures? Ideally you also want to have some corroboration in fossil or archeological evidence, although this is often impossible.
Second, is there is indeed a mismatch—can some generalization can be made about advanced industrial states indicating a change since the hunting-gathering era? Third, you want to know if the change matters, and if so, how it matters. These things have to be gone about very carefully, since many people tend toward ethnographic romanticism—a desire to believe that things were better (more “natural”) in the distant past.
In my talk, I applied these three questions to three domains of human experience, in order to show how I think about these things; diet, exercise and health; infancy and childhood; and mental health. I will consider the first domain here and return to the others in the future.
It was clear that the !Kung, despite their high mortality from infectious disease, were otherwise very strong and fit for most of their lives. When moved to Atlanta I met Boyd Eaton, a physician who had been working on hunter-gatherer diet and lifestyle; he inspired me to begin a collaboration that changed my life.
In a series of papers like “Paleolithic Nutrition” and “Stone Agers in the Fast Lane”and in a book called The Paleolithic Prescription, we (along with Marjorie Shostak and others) showed that, compared with modern Western diets, hunter-gatherers had much lower levels of carbohydrate and salt, much higher levels of protein and fiber, a much higher ratio of polyunsaturated to saturated fat, and a broader spectrum of needed vitamins and micronutrients.
Furthermore, hunter-gatherer serum cholesterol levels were under 150, their aerobic fitness was like that of college athletes and remained very high throughout life, their diabetes prevalence was far lower than ours, and their blood pressure did not increase with age as in the West. These and many other findings suggested that our ancestral diet and activity once protected us from many chronic “diseases of civilization” that afflict us in our kind of culture.
So the answer to the first two questions was “Yes.” But this did not prove that the change mattered. Epidemiological data on contemporary populations strongly suggested that our hypothesis was right, but experiments were needed—animal experiments and randomized, controlled human trials. Many studies have shown that if you improve diet and lifestyle from a typical Western starting point you improve health measures—even a reversing coronary artery disease and diabetes.
One result has been a change in official recommendations. Twenty years ago when we first began to publish our results, official advice would already have tended to push Americans in a hunter-gatherer direction on most measures. But since then, research has moved the advice more in the hunter-gatherer direction. In other words, we can say, “We told you so.”
But the most satisfying result so far was a study published last September by Steffan Lindeberg, a physician in Lund, Sweden, and his colleagues. They randomly assigned diabetics to one of two diets: the Consensus diet, a Mediterranean-like diet consisting of whole grains, low-fat dairy products, vegetables, fruits, fish, oils and margarines, and the Paleolithic diet, based on our publications, consisting of lean meat, fish, fruits, vegetables, root vegetables, eggs and nuts.
After twelve weeks, both groups had significantly decreased their waist circumference, with the Paleolithic diet group getting slimmer than the Mediterranean group. But the biggest difference was in the classic short-term test for diabetes: glucose tolerance improved seven percent on the Mediterranean diet, but 26 percent on the Paleolithic diet, independent of the change in waist circumference.
This is an astounding result, with implications for our future as a species, given the our rapidly rising diabetes prevalence and the heart disease that follows. Many years ago Karin O’Dea had already done an elegant experiment in which diabetic Australian aborigines were taken back to the bush to return to their traditional hunter-gatherer diet; their diabetes improved markedly.
But Lindeberg’s team randomly assigned ordinary Swedish patients to mimic a hunter-gatherer diet they had never tried before, and compared them to patients on the standard recommended diet. This was the first-ever head-to-head experimental comparison, and the Paleolithic diet won.
I’ll return to all these questions in future entries, but for now the Swedish study could signal a turning point in the history of our species, if it helps avert an epidemic of chronic disease by turning back to our origins to find a healthier future.