Early signs of vitamin C deficiency often go unrecognized and may manifest as a reduced desire to be physically active. Moreover, it is often associated with increased cold duration and severity. A study conducted by several American institutes investigated the effects of vitamin C supplementation on physical activity and respiratory tract infections during the cold season. Non-smoking adult men, aged 18-35 years, with plasma vitamin C concentrations less than 45 µmol/L received either 1000 mg of vitamin C daily or a placebo. After eight weeks, vitamin C concentrations were increased significantly in the test group. Physical activity also increased during the trial. In addition, the incidence of colds decreased, and the cold duration was reduced by 59% in the test group compared to the placebo group. The results suggest significant health advantages associated with vitamin C supplementation in people with adequate-to-low vitamin C status. More details can be found in the study.
Johnston et al.