Vitamin C functions in enzyme activation, oxidative stress reduction, and immune function. There is considerable evidence that vitamin C protects against respiratory tract infections and reduces risk for cardiovascular disease and some cancers. Current trials are examining the efficacy of intravenous vitamin C as cancer therapy. Many experts believe that the recommended intakes for vitamin C (45 to 90 mg daily) are several orders of magnitude too low to support optimal vitamin C functionality. Also, there is a misperception that vitamin C deficiency disease (scurvy) is largely historical and rarely observed in developed nations. Physical symptoms of scurvy include swelling of the lower extremities, bleeding gums, fatigue, and hemorrhaging, as well as psychological problems, including depression, hysteria, and social introversion. The long-term safety of vitamin C supplementation seems evident as large investigations have noted reduced risk of mortality in vitamin C supplementing populations and in those with elevated plasma vitamin C concentrations.

Fruit and vegetable consumption has been shown to predict physical activity (PA) in college students. This study examined the specific association between plasma vitamin C, found predominately in fruits and vegetables, and indices of PA in college students. Fifty healthy, non‐smoking men who did not take vitamin supplements or engage in regular vigorous activity were recruited. Participants (23.2±0.6 y; 24.7±0.5 kg/m2) provided a fasting blood sample and a 24‐h recall, and completed PA assessments including a step test. Participants were fitted with a pedometer and recorded steps for three complete days. Vitamin C concentrations ranged from 12 to 50 μmol/L. Diet quality was not correlated with plasma or dietary vitamin C. Participants with inadequate vitamin C status (<28 μmol/L, n=21) had significantly lower fitness levels and daily step counts, and were less likely to engage in moderate‐to‐vigorous exercise compared to vitamin C‐adequate peers. These relationships between vitamin C status and PA were independent of diet quality and fruit and vegetable consumption. These data indicate that college men are at risk for marginal vitamin C status, a condition linked to reduced fitness and PA.