When Vitamins Backfire

Vitamin Packaging

Concept packaging by Colin Dunn, CC-BY

Bad news for athletes this week: two studies show that vitamin supplements can interfere with the benefits of exercise. While vitamins are safer and cheaper than many other supplements sold to athletes, these studies add to the growing body of evidence that more of a good thing isn’t necessarily better. And even though we think we understand what vitamins do, their real-world effects highlight how murky our understanding of human biology really is.

Take the study that came out Sunday on Vitamin C and E supplements. As antioxidants, these vitamins are often recommended as recovery aids and for general health. But the new study seemed to show the opposite effect: the supplements interfered with runners’ training (as measured by molecular markers, though not performance tests) The authors write “The exact mechanism behind this effect is not possible to decipher. However … we assume that the antioxidants attenuated the generation of reactive oxygen and/or nitrogen species.” In other words, the vitamins neutralized the free radicals that are generally thought of as bad guys. But free radicals may be a good thing in the context of exercise, and antioxidants a bad choice.

The other recent study was apparently meant to rubber-stamp a Dole product, mushroom powder containing high doses of Vitamin D2. It likewise backfired on the subjects who took it, in this case NASCAR pit crew athletes. The D2 was supposed to convert to D3 in their bodies and this, in turn, was supposed to decrease muscle damage and help them recover faster from their strenuous workouts. Instead, it lowered D3 and increased muscle damage, and ultimately made no difference in strength.

In December, an Annals of Internal Medicine editorial cried out: Enough is enough: Stop wasting money on vitamin and mineral supplements. The authors concluded that multivitamins don’t prevent dementia, heart disease, or cancer; but certain vitamins can be harmful in large doses. The jury is still out on Vitamin D, they wrote, but for all the rest, taking them on top of a reasonable diet carries no benefit and may be harmful.

Squeaky clean?

I’m not calling vitamins useless; they’re crucial for treating deficiencies, and preventing deficiencies in populations at risk. For example, the World Health Organization recognizes Vitamin A deficiency as a public health problem in more than half of all countries, and the leading cause of preventable blindness in children. To combat it, they promote breastfeeding, nutrient-rich diets, and, yes, supplementation.

But the situation is very different for well-fed health seekers. Studies that intended to test how well Vitamin A can prevent lung cancer in smokers ended up showing that Vitamin A supplementation increases the risk of cancer.

And there’s the conflict: while public health messages promote vitamins to correct deficiencies, the actual health-seeking public latches on to vitamins as squeaky clean supplements that can do no wrong. Take them as insurance against gaps in your diet, suggest many experts.

A similar logic is behind the alleged trend of getting a Vitamin B12 shot if you’re feeling “sick and tired of being sick and tired.” (Reality check: this only works if you have a real deficiency, which most people don’t.) Likewise taking Airborne if somebody around you is sick; its main ingredient Vitamin C doesn’t actually keep you from getting sick. But at least you feel like you’re doing something, right?

I can’t help thinking vitamins are a pawn in non-health-related schemes: selling products that look better because they’re fortified (my favorite example: Diet Coke Plus), or selling something that makes you feel like you have an edge over the competition (as in athletic supplements) or power against disease (like Airborne). Vitamins are approved as safe, so manufacturers can easily sell them with claims hinting at health. You can make money selling Airborne. A pamphlet on hand-washing would probably work better to prevent catching a cold, but is hardly as lucrative.

[Correction: About an hour after this post was first published, I added the clarification about molecular markers in the second paragraph]

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