Here’s a puzzle. Let’s say you’re trying to get your nutrition “in balance”. You’re told that there are daily reference values of macronutrients (like protein, carbs, and fats) that you should try to consume. Along with that, you’re told you should try to hit certain targets for micronutrients (like vitamins and minerals) as well.
But you’re not told that the one affects the other.
In the last century, anthropologists have had the opportunity to study cultures, such as the Inuit, whose diets consist of nearly 100% meat (along with trying out this lifestyle themselves), and nutrition scientists have tested such a diet several times. Aside from the weight-control and blood-pressure benefits observed, the subjects had no vitamin deficiencies.
Why? As Gary Taubes notes in GCBC:
…[A]nimal foods contain all of the essential amino acids (the basic structural building blocks of proteins), and they do so in the ratios that maximize their utility to humans. They also contain twelve of the thirteen essential vitamins in large quantities. Meat is a particularly concentrated source of vitamins A, E, and the entire complex of B vitamins. Vitamins D and B12 are found only in animal products (although we can usually get sufficient vitamin D from the effect of sunlight on our skin). [GCBC, Ch. 19, pp. 321-2; emphasis in original; footnote elided]
Well, what’s wrong with that? We can eat some meat to get vitamins, and also mix in some grains, veggies, and fruits for “balance”, right? Not so fast. It turns out that carbs compete with your body for vitamins.
Nutritionists would establish by the late 1930s that B vitamins are depleted from the body by the consumption of carbohydrates. “There is an increased need for these vitamins when more carbohydrate in the diet is consumed,” as Theodore Van Itallie of Columbia University testified to McGovern’s Select Committee in 1973. A similar argument can now be made for vitamin C….
[T]here is significant reason to believe that the key factor determining the level of vitamin C in our cells and tissues is not how much or little we happen to be consuming in our diet, but whether the starches and refined carbohydrates in our diet serve to flush vitamin C out of our system, while simultaneously inhibiting the use of what vitamin C we do have. [Ibid., pp. 325-6]
So what is the U.S. Food and Drug Administration trying to achieve when they give nutrition advice like this?
Beats me. But it sure seems like a funny way to execute on their mission.