Vitamin C is marketed as a dietary supplement, partly because of its ‘antioxidant’ properties. However, we report here that vitamin C administered as a dietary sup-plement to healthy humans exhibits a pro-oxidant, as well as an antioxidant, effect in vivo.
We conducted a study involving 30 healthy volunteers (16 females and 14 males aged between 17 and 49) whose diets were supplemented with 500 milligrams per day of vitamin C (ascorbic acid) for 6 weeks. We assessed the levels of oxidative damage to peripheral blood lymphocytes in terms of modified DNA bases. The level of 8-oxoguanine was found to decrease on sup-plementation relative to both placebo (calcium carbonate; 500 mg per day for 6 weeks) and baseline measurements, where-as the level of 8-oxoadenine increased.