Increased vitamin C intakes may improve physical activity

A new US study reports that a supplementation with vitamin C in men with low vitamin C blood levels may improve physical conditions and decrease the incidence and duration of colds.

The randomized controlled trial measured the physical activity and documented cases of colds among
28 healthy non-smoking men aged between 18 and 35 with adequate to low plasma vitamin C concentrations (below 45 micromoles per liter) who took a vitamin C dose of 1,000 mg per day or a placebo for eight weeks (1). The study results showed an up to 40% increase in the physical activity parameters for participants of the vitamin C group with low vitamin C levels at the start of the study, compared with the placebo group. Furthermore, fewer people in the vitamin C group reported cold episodes, and duration of the colds was reduced by an average of 59% in the vitamin C group compared with the placebo group.

The researchers commented that the role of vitamin C in promoting physical activity may relate to its antioxidant properties since oxidative stress is related to fatigue. Vitamin C is also thought to possess neuroprotective properties and influences the brain’s oxidative fuel supply, processes that may influence a sense of wellbeing. Based on the evidence to date, it may be that only populations with low vitamin C status, or those experiencing extreme physical exertion or cold stress, may experience anti-cold benefits of vitamin C. Earlier research has generated controversial results: a review of 29 trials concluded that vitamin C may reduce the risk of developing common cold for marathon runners by 50% (2).

1. Johnston C. S. et al. Vitamin C Supplementation Slightly Improves Physical Activity Levels and Reduces Cold Incidence in Men with Marginal Vitamin C Status: A Randomized Controlled Trial. Nutrients. 2014;
   6(7):2572–2583.
2. Hemilä H. and Chalker E. Vitamin C for preventing and treating the common cold. Cochrane Database Syst Rev. 2013; CD000980.pub4.