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.
The conspiracy theorist in me would say that Big Pharma “made” the FDA push a diet that created a generation of obese diabetics. More likely, it was lousy epidemiologists who concluded fat was bad. And then all their buddies knew they were correct and didn’t check. Carbs, smoking, mortgage backed securities, the list is endless. It brings to mind this XKCD strip http://xkcd.com/531/
Of course, Gary Taubes is not a nutritionist, nor do his views represent the current mainstream thinking on nutrition. Which is not to say that he is wrong, just that the jury is still out. Which also means that it is hardly surprising if the FDA is promoting a regimen that is in conflict with his point of view.
Nutrition is very complex, and made tougher by virtue of genetic diversity, and the fact that it is difficult to control all the variables in any study.
On the other hand, it is interesting to reflect that for all the emphasis nutritionist’s place on vitamins, from an evolutionary perspective it is precisely because vitamins are so unimportant that the ability to synthesize them was jettisoned from our metabolisms. They are the chemicals that cost more energy to make than to just gather them from the environment.
Agreed that nutrition is complex and people differ; also, studies around diet have the added disadvantage that you can’t usually do them with placebos and double-blind.
That said, I think Taubes has done the best job of anybody of assembling the actual knowledge we do have today. The book works very hard not to present his “views”, but rather a review of the actual scientific literature and how it stacks up against different hypotheses. It doesn’t seem particularly controversial (scientifically speaking), nor was it just newly discovered, that absorption of many vitamins is impacted by carbs.
If you have seen any research that disputes the point Taubes quoted from the 1970s and which I quoted in turn, please do let me know; I’m trying to take a look at primary research where possible.
(Funny XKCD!)
Just came across this NY Times column (Public Policy That Makes Test Subjects of Us All) that shows how scientific experimentation on nutrition definitely shouldn’t be done. Yikes.
On Carbohydrates….Ahhhh how simple it is if you can just control it. Carbohydrates fuel the brain because the brain needs some sugar Right!! So there are certain times of the day where a carbohydrate meal would be great for a lot of reasons. You may get a lot of vitamins and minerals like you said but some will fight with the others for absorption, so why fight this subject. Just like protein supplements, Niacin, and pyridoxine, deplete the Glycogen stores. And when that happens; you most likely will feel like I do before a show. Energy Deficient. Also when you do low carb you will also have a bigger rebound when you go to normal eating. Another thing is that you can throw some things out of balance if you low carb incorrectly and how many people do you think research it enough to do it correct?
-insulin guy-
Hi Insulin Guy! Glad to see you back here!
Note that it’s a misconception that the brain needs us to eat carbs just because it requires glucose as fuel (I hope to post on this soon). However, I agree that there’s a rebound problem that lasts a couple of days if you eat low-carb and then fall off the wagon (or simply return to formerly high levels of carb intake). Finally, given that no one has yet shown an all-meat diet to have any ill consequences or vitamin deficiencies, I’m not sure it’s all that hard to do low-carb right. :-)