Effects of exercise on riboflavin requirements of young women

The riboflavin requirement of young women during periods of sedentary living and exercise was determined during a 12-wk metabolic study. The study was divided into a 6-wk no exercise period followed by a 6-wk exercise period in which subjects jogged around a track for 20 to 50 min/day. Twelve subjects, aged 19 to 27 yr, were fed a basic diet containing 0.6 mg riboflavin/1000 kcal of intake. Riboflavin intake was increased by 0.2 mg/1000 kcal increments by provision of riboflavin in a glucose polymer mixture. Linear regression analysis was used to estimate the riboflavin intake required for an erythrocyte glutathione reductase activity coefficient of 1.25 during both the no exercise and exercise periods. Individual riboflavin requirements ranged from 0.62 to 1.21 mg/1000 kcal before exercise and 0.63 to 1.4 mg/1000 kcal during the exercise periods. Riboflavin requirement could not be related to the kilocalorie intake or lean body mass of the subjects. It is concluded that healthy young women require more riboflavin to achieve biochemical normality than the 1980 Recommended Dietary Allowances and that exercise increases riboflavin requirements.