Biology: March 2009 Archives


March 16, 2009

Perry Metzger (via Mangan's and Patri Friedman) points me to this paper on the impact of Vitamin C on endurance training. The basic result is that Vitamin C supplementation in rats seems to significantly decrease the effect of endurance training. The hypothesized (though they have expression studies to back it up) mechanism is that the production of free radicals during exercise stimulates mitochondrial development in the muscle and that taking antioxidants interferes with this mechanism, resulting in a reduced training effect: there isn't a significant impact on VO2max, but rats treated with training along will run significantly longer than those treated with training plus vitamin C (where the test is a forced treadmill run with shock as incentive.) The authors also did a small human study, and the vitamin C group performs worse but the results aren't statistically significant.

Some initial thoughts:

  • Obviously, it would be nice to see a bigger trial on humans.
  • The study was done on untrained rats and humans. It would be interesting to see a similar study with trained athletes to see if there is any difference.
  • One of the reasons that athletes tend to supplement with C is on the theory that it improves immune function. Getting sick even once has a huge impact on your training cycle. I don't think the data on immune function is really that convincing, but to the extent to which C does prevent you getting sick, you would need to balance that against the impact on training.
  • If C inhibits the training effect, what impact does it have in the post-training period? Is there an argument for some sort of vitamin C cycling?

All that said, I recently ran out of vitamin C and this is making me rethink, at least a little, whether I want to buy more.