For a long time I understood nutrition to be “what you do to avoid getting fat.” A few years ago I realized that my body gravitates toward a low weight, so I could eat literally anything I wanted and not gain weight. In fact, I tried to gain weight and failed.
More recently, I’ve started to realize that there are other bad things that can happen to me: mostly diabetes and cardiovascular disease.
I’ve also realized that the data on long-term nutrition is much less clear than anyone would like. Does cholesterol give you heart disease? Unclear. Does salt give you high blood pressure? Unclear. An ideal study would randomly assign people to a particular diet and follow them over the course of their lifetimes, but it’s too hard to run that kind of study. So we have population studies instead, which indicate that any number of things might be good for you. The Mediterranean countries of Europe have low rates of heart disease, which has been attributed to lots of plants, olive oil, and wine. But the Inuit have a rate of heart disease similar to other people despite eating a diet made largely of fish and blubber with almost no plant material.
Part of my shifting sense of nutrition is an effect of who I spend time with. When I was hanging out with vegans, I was sure that eggs were bad for me. Now that I have friends who literally consider bacon a health food, cholesterol doesn’t seem as scary. But I shouldn’t just be averaging my friends’ eating habits to create some kind of middle way.
For a while I was going on Michael Pollan’s advice which was to basically eat like your great-grandparents did (“Eat food, not too much, mostly plants.” He advocates staying away from processed food and weird chemicals).
But what they ate doesn’t sound healthier than what I eat. Laura Ingalls Wilder describes a meal of the 1860s:
“Almanzo ate the sweet, mellow baked beans. He at the bit of salt pork that melted like cream in his mouth. He ate mealy boiled potatoes, with brown ham-gravy. He ate the ham. He bit deep into velvety bread spread with sleek butter, and he ate the crisp golden crust. He demolished a tall heap of pale mashed turnips, and a hill of stewed yellow pumpkin. Then he sighed, and tucked his napkin deeper into the neckband of his red waist. And he ate plum preserves, and strawberry jam, and grape jelly, and spiced watermelon-rind pickles. He felt very comfortable inside. Slowly he ate a large piece of pumpkin pie.”
Plenty of cholesterol, salt, sugar, and refined starches there. It did also have some vegetables, which a meal at Burger King probably wouldn’t.
Probably the only thing all traditional cultures have in common is not diet, but exercise. Almanzo Wilder could demolish a dinner that size because he had been working on a farm all day. When it comes to explaining modern disease rates, sedentary lifestyles are probably way more dangerous than red dye #40.
The other thing that people seem to agree on is that sugar is bad for you, and specifically a lot of sugar hitting your bloodstream at once is bad for you. I’m not sure the kind of sugar matters that much, though. People are willing to pay extra money for “sugar in the raw”, which as far as I can tell is just browner than regular sugar and not any better for you. They also get creeped out by high-fructose corn syrup, although they’re perfectly happy to get the same fructose in the form of an apple.
Lately I’ve been paying more attention to glycemic index, which is the rate at which foods increase your blood sugar. It’s not just “sugar” that does it, but starchy foods that quickly break down into sugars — flour, potatoes, rice. Bizarrely, the glycemic index of foods doesn’t just depend on their ingredients — wheat in the form of pasta is apparently better for you than in the form of bread. And other foods, like fats and acids, can slow down your sugar spike.