Riboflavin status of adolescent southern Chinese: riboflavin saturation studies.

Riboflavin saturation studies were done on 36 high-school boys in Canton whose mean daily intake of riboflavin was 0.45 mg and who showed clinical evidence of deficiency. The boys were given a 2 mg load of riboflavin orally followed by supplements of 0.5, 1.0 and 1.5 mg riboflavin to three groups; a control group received no supplement. After 14 days' supplementation, excretion of riboflavin had increased significantly in all supplemented groups, but not in the control group. The 4-h excretion of riboflavin after the 2 mg load averaged 8.6 per cent of the load for all groups before supplementation. After 14 days' supplementation it was significantly increased only in the groups receiving 1.0 and 1.5 mg daily. This suggests that tissue saturation may not be achieved until the background intake of 0.45 mg/d is increased by between a further 0.5-1.0 mg daily. After 17 days' supplementation with 1.0 and 1.5 mg riboflavin, scrotal dermatitis disappeared. However, even in the 0.5 mg supplemented group, eight out of ten boys with scrotal dermatitis had responded and a total intake of 0.95 mg/d may be enough to prevent clinical deficiency.