Toxic Antioxidants?

Intense exercise, particularly if it involves an eccentric component, results in severe muscle inflammation. That leads to the migration of white blood cells into the muscle, some of which promote reactions that result in by-products of oxygen metabolism called free radicals. The free radicals, in turn, worsen muscle inflammation.

The body deals with excessive free-radical production through several built-in antioxidants, such as superoxide dismutase and glutathione. Research shows that taking dietary antioxidants, such as vitamins C and E, the mineral selenium and others, helps to neutralize the rampant free-radical reactions in muscle following exercise. That, in turn, decreases muscle inflammation and promotes recovery.

Studies show that free iron stored in the muscle may also be released. Under normal conditions iron is tightly bound to several proteins, such as ferritin, transferrin and albumin. In the muscle iron is attached to another protein called myoglobin. When the muscle is damaged, however, the iron normally bound to myoglobin and other proteins is released, which is dangerous because the iron can react with oxygen to produce free radicals that attack numerous cells and tissues in the body.

Many bodybuilders take supplements right after exercise. A new study warns, however, that two particular antioxidants, vitamin C and N-acetyl-cysteine (NAC), may react with free iron produced in muscle and become pro-oxidants’meaning that they produce free radicals.1 Normally, both vitamin C and NAC are potent antioxidants. NAC, in fact, is a nutritional precursor of glutathione.

But according to the study, which measured oxidation reactions and inflammation in human subjects who took both vitamin C and NAC following eccentric arm curls, those nutrients appeared to accentuate the damage caused by the intense exercise, promoting free-radical production with free iron.

The study overlooks a major aspect of antioxidant use, however: No antioxidant works in a vacuum. They all work together, and taking individual antioxidants without the backup of other nutrients may produce paradoxical effects, as this study illustrated. A similar scenario occurred a few years ago, when long-term smokers were given beta-carotene, which produced higher death rates among the smokers because it acted as a pro-oxidant instead of an antioxidant.

The lesson is that when you use antioxidants, use them as a group, since they offer overlapping protection, keeping each other stable and thus preventing the kinds of reactions that occurred in these studies.

1 Childs, A., et al. (2001). Supplementation with vitamin C and N-acetyl-cysteine increases oxidative stress in humans after an acute muscle injury induced by eccentric exercise. Free Rad Biol Med. 31:745-53.