I think many of us assume that if experts say that Vitamin C can boost the immune system, then grabbing a 500mg bottle at your local health nutrition store must be a good idea. I know I've been guilty of this mindset. But it turns out that if you exercise, taking antioxidant vitamins might not be in your best interest. There was a good summary by Derek Lowe at 'In The Pipeline' about a new PNAS paper that argues against popping vitamins while engaged in an exercise routine. The study found that the experimental group that took a combination of Vitamin C and Vitamin E actually lost some of the inherent benefits of exercise, such as changes in insulin sensitivity and formation of natural antioxidants. My only criticism of the study is that Vitamin C is capable of regenerating Vitamin E, so I wonder whether this phenomenon will carry through for all supplemental antioxidants, or if it's limited to the particular vitamins used in this study.
I see a recurring theme in the articles that pique my interest these days, and I can't help but wonder, yet again, if this is another example of the differences of nutrients that exist in nature, and those made in a lab? Should we be getting our vitamins from foods instead of supplemental pills?