When Spaniards brought maize to the Old World, they failed to import the traditional wisdom for processing the corn to make the niacin bioavailable. Wherever corn consumption spread in Europe, a disease called pellagra became endemic. Hundreds of years later, when the cause of the condition was proven by Western science, instead of using the ancient method of nixtamalization to process corn meal, niacin was added.
The way nutrients were first discovered was through industrial food. White rice, flour, and sugar started off as luxury goods. They were “refined” in both senses of the word: undesirable matter was discarded, and the resulting product was smoother and more appealing. At first only the rich could afford them, but as demand grew for the refined foods, scale of production increased and prices dropped. When these industrial foods were produced on a large enough scale that everyone could afford them, they became so cheap that they became staples of the very poor. And that is when we started to see how poor these new foods really were, because people who lived on them developed diseases of malnutrition.
Diseases of malnutrition don't always have very obvious signs, so it took a while for scientists to piece together the clues. When people living on white rice developed a range of symptoms, including difficulty walking, sufferers called it “beriberi.” The condition was cured with thiamin, which is found in rice bran, but which is removed from white rice. White rice was adopted by industry because it stores for longer periods than brown rice, so instead of switching people back to brown rice, with its shorter shelf life and lower profit margin (corporations make money by "adding value," i.e. processing, to raw ingredients), they solved the problem more cheaply and profitably ("Now with thiamin!") by fortifying white rice with thiamin.
And so it went, learning from one mistake after another, and then finally through concentrated study, what parts make up food, their functions in the body, what in food can be dangerous, and how much and what kinds are needed for health. "Nutritionism" is the belief that our need for food can be deconstructed into a finite number of irreducible and replicable substances called “nutrients,” which may be assembled in any order convenient for manufacture. For many years now, ready-to-eat breakfast cereals have been supplemented with vitamins and minerals, justified by the tenets of nutritionism. The additives in Captain Crunch are typical: niacinamide, reduced iron, zinc oxide, thiamin mononitrate, pyridoxine hydrochloride, riboflavin and folic acid. Many are in forms chemically distinct from the forms found in food, and in some cases, we even know that the body doesn’t use the synthetic, supplementary nutrient in the same way as when these nutrients are found in our food.
Under nutritionism, any compound in a food can be isolated, separated, and either concentrated as a nutrient (i.e. soy protein isolate) or discarded as undesirable (i.e. fat-free milk). Which nutrients we value, and which we abhor, change like trends in politics and skirt lengths. Fiber wasn't valued by those who refined rice, considering it an inefficiency in getting enough energy in one's diet, but today it's added to foods as a supplement. In the 1980s, everyone feared fat and dieters ate big plates of pasta and baked potatoes. Since then, the tide has completely turned on carbohydrates, while we retain fear of both fat and calories. It creates anxiety around food to be afraid of most macronutrients, a fear that industry nurtures and is glad to assuage with their highly processed offerings.
The ultimate faith act in nutritionism is to attempt to live on nothing but industrial meal replacement. But to do so would be folly: the evidence suggests that industrial food is causing a whole new set of diseases today, from diabetes to cancer. The pace of change in our diets has grown exponentially: so quickly that we can’t even reliably look to our oldest living relatives for a model of a sustainable diet. Nutritionism sells peace of mind, with their certainty that science has just unlocked the nutrient you need to add to your shopping cart.
We won’t find the answers to our health care crisis in the industrial model, because the machines of capitalism don't back up: they can only plow forward, doing what machines do, which is make more products to sell. Just as industry's answer to beriberi is fortified, sugar-sweetened, chemically preserved grain flour, they have an answer equally appetizing and easy to manufacture for heart disease, breast cancer, or diabetes. They'll even sell you food for obesity. As Michael Pollan points out in his famous essay, “Unhappy Meals,” the fact that an industrial food product has a label and makes health claims should make it suspect. It's a product first, not a food.
What we know about nutrition may be wrong, and is certainly incomplete. However, we know a great deal about food.
So: Eat food. The rest is commentary.