Abstract
The number of people taking large amounts of vitamin supplements is increasing in Japan. Taking large amounts of water-soluble vitamins is not considered risky because excess water-soluble vitamins are quickly excreted in the urine. In the present study, we investigated the clearance of water-soluble vitamins in Japanese. In the first week, six young female subjects ate the diet. In the second week, they ate the same diet with 6 times the recommended water-soluble vitamin dose based on the Dietary Reference Intake (DRI) for Japanese. In the third week, they ate the same diet without the vitamin mixture. The 24-h urine samples were collected every week. All water-soluble vitamins except vitamin B_<12> in 24-h urine samples were measured. The urinary excretion of nicotinamide metabolites, biotin, and ascorbic acid in the third week was same as that in the first week. Urinary thiamin in the third week was 4.4 times higher than in the first week, riboflavin was 3.4 times, vitamin B_6 metabolite 4-pyridoxic acid 2.0 times, pantothenic acid 2.4 times, and folic acid 3.1 times.
