Monday, December 19, 2011

Antioxidants are more complicated than we thought

sweatscience.com

I wrote last month about emerging evidence that taking antioxidant supplements may actually be counterproductive, especially for athletes. There’s an interesting paper coming up in Cell Metabolism that casts further doubt on the whole basis of our belief that (a) oxidative stress is what causes aging and other cellular damage, and (b) antioxidants can counteract these effects (press release here; abstract here).

What’s new about the study is that they didn’t use the typical indirect methods to guess about levels of reactive oxygen species (ROS – the bad guys) and antioxidants, averaged over the entire body. Using transgenic fruit flies, they were able to measure ROS activity directly and in real time, in different parts of the body. There are a whole bunch of surprising results in this study that fly in the face of the conventional antioxidant theory. A few of the key ones:

If oxidation is linked to aging, we’d expect to see more ROS as the flies get older. In fact, ROS levels stay constant throughout the aging process except in the intestine. Only the intestine shows gradually increasing levels of oxidation.
Even in the intestine, the flies who lived longest had ROS levels that increased more quickly than the flies who died earliest — exactly the opposite of what we’d expect if oxidative stress is linked to aging and eventual death.
When the flies were fed an antioxidant, their production of ROS increased in response.

This last point, of course, is most interesting from the perspective of supplementation. It suggests that there’s a homeostatic response that attempts to preserve the balance between oxidants and antioxidants at a roughly constant level. So if you take a lot of antioxidants, your body simply ramps up its level of oxidants in response — with who knows what effect!

Let me emphasize: this is a study of fruit flies. Fruit flies are not humans. Still, the results suggest that our basic understanding of the real-time dynamics of oxidant-antioxidant interactions is far from complete. Now, I’d happily ignore all this cell biology stuff if there were lots of controlled trials showing increased health or performance from antioxidants. If it works, who cares about the mechanism? But since (a) we have no consistent evidence that antioxidants work, and (b) it’s increasingly clear that we don’t even understand how or why they should work, or what supposed problem they’re supposed to fix, I still think a balanced diet with lots of brightly coloured fruits and veggies in the way to go. Not powders, and not pills.

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