Monday, July 22, 2013

Eat Food, Not Too Much, Mostly Plants

This is the subtitle to Michael Pollan’s book In Defense of Food. Those seven words delineate a perfectly adequate diet: for anyone; for anyone interested in saving the planet; and for borderline diabetics.

Last winter I was diagnosed with the beginning of diabetes. I am not yet at the stage that requires any medication, and the fact that since that time I have lost 20 pounds might mean that I am safe. My response is to find creative solutions that I can enjoy. I am posting occasional entries about diabetes on this site if they relate to evolution and/or to the environment in which we have evolved and in which we live. I am not turning this blog into a diabetes forum.

Diabetes is considered to be a disease of civilization. That is, many scientists believe it results from physiological adaptations that were perfectly good in the Stone Age but which are maladaptive for civilized people. I can see that this argument makes sense for obesity. The ability to store food in the form of fat, during a time of feasting, and then use it up later during famine, was utterly essential in the Stone Age, when your tribe might get to feast on a dead mammoth then have nothing for a long time. But today, when food is continuously available, obesity results from fat storage. As Pollan said in The Omnivore’s Dilemma, our bodies are preparing for a famine that never comes. Not only that, but fat storage was a sign of affluence in the Stone Age; being fat was therefore attractive to potential mates. There is a fair amount of Paleolithic pornography to this effect. Therefore both natural and sexual selection favored the potential for obesity in Paleolithic times.

But diabetes? How could the inability to control blood sugar levels be adaptive under any set of conditions? Some scientists say that having high blood sugar levels (that is, a reduced ability of cells to absorb and use the sugar) was adaptive because it kept our Stone Age ancestors from using up their blood sugar too fast. Sorry, but this sounds like one of those just-so stories that modern evolutionary science is trying to get away from. The nascent science of evolutionary medicine would be well served to leave such stories behind. Of course, I could be wrong, in which case I will post a revision of the opinion here stated. Diabetics need to eat lots of small meals; this is precisely what our Stone Age forebears did not always have the luxury of doing, especially when they spent all day chasing down big game and when wild grains, roots, nuts, and berries were unavailable.

Some people propose that we adopt the Paleolithic Diet. Without going into detail, I’ll just say that this is not too useful unless you adopt the Paleolithic Lifestyle—running through the forest or across the savanna all day.

Michael Pollan’s advice, to eat food, not too much, most plants, is good advice for all of us. People with diabetic tendencies could include a bias against starch and sugar.

I will be participating in Botany 2013, the big meeting of botanists, starting next weekend. If I have a chance, I will blog from there.

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