Michael Pollan explains the problem with nutritionism:
The problem starts with the nutrient. Most nutritional science involves studying one nutrient at a time, a seemingly unavoidable approach that even nutritionists who do it will tell you is deeply flawed. “The problem with nutrient-by-nutrient nutrition science,” points out Marion Nestle, a New York University nutritionist, “is that it takes the nutrient out of the context of the food, the food out of the context of the diet, and the diet out of the context of the lifestyle.”
If nutrition scientists know this, why do they do it anyway? Because a nutrient bias is built into the way science is done. Scientists study variables they can isolate; if they can’t isolate a variable, they won’t be able to tell whether its presence or absence is meaningful. Yet even the simplest food is a hopelessly complicated thing to analyze, a virtual wilderness of chemical compounds, many of which exist in intricate and dynamic relation to one another, and all of which together are in the process of changing from one state to another. (62)
Of all the things I’ve taken issue with in In Defense of Food, this is probably the one that most consistently makes me cringe each time I read it. The problem is that everything Pollan says about the complexity of foods actually works against his thesis. To claim that a food is “a virtual wilderness of chemical compounds, many of which exist in intricate and dynamic relation to one another” is to say that the chemical compounds in foods are difficult to isolate. Foods, by contrast, are relatively easy to isolate because when scientists study the effects of foods as a whole they take a pass on analyzing that “hopelessly complicated thing.”
So if you’re a nutrition scientist you do the only thing you can do, given the tools at your disposal: Break the thing down into its component parts and study those one by one, even if that means ignoring subtle interactions and contexts and the fact that the whole may well be more than, or maybe just different from, the sum of its parts. (62)
In reality, nutrition scientists often do study whole foods and broader dietary patterns, which is why Pollan can claim on the very next page that “researchers have long believe that a diet containing lots of fruits and vegetables confers some protection against cancer.” It’s also wrong to say that nutrients can only be studied one by one; Pollan will later tell us about interactions betwen omega-6 and omega-3 fatty acids.
That said, researchers do expend considerable effort with the nutrient-by-nutrient approach, even if not for the reasons that Pollan cites. Frank Hu and Walter Willett of the Harvard School of Public Health justified this choice in a letter (included in Pollan’s references) responding to T. Colin Campbell’s criticism of reductionism:
Although we agree that overall dietary patters are also important in determining disease risk, we believe that identification of associations with individual nutrients should be the first step because it is the specific compounds or groups of compounds that are fundamentally related to the pathophysiology of the disease. Specific components of diet can be modified, and individuals and the food industry are actively doing so. Understanding the health effects of specific dietary changes, which Campbell refers to as “reductionism,” is therefore an important undertaking.
Not being a dietitian or a public health expert, I’m not going to try to evaluate the merits of this argument. What I think is significant here is that Pollan has invented his own dubious argument for focusing on nutrients instead of discussing an argument that researchers actually use. By doing so, not only does he fail to address the real argument, but he also opens the door to a broader dismissal of scientific inquiry on questions of nutrition.