VITAMINS

Vitamins are defined as essential organic micronutrients that are not synthesized by mammals. Coenzymes are organic compounds with low molecular weight that are required to show enzyme activities by reversibly binding with their apoenzymes, and are derived mainly from compounds of vitamin B group. Most of coenzymes show various biofunctions besides their functions as coenzymes. Accordingly, it is more appropriate to regard them as effective biofactors. Pyridoxal phosphate serves as an inhibitor of catepsins, and regulates the gene expression. Several novel built-in coenzymes such as topaquinone and lysine tyrosylquinone have been demonstrated in mammalian and microbial enzymes.

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Intakes and plasma concentrations of antioxidant vitamins in 12 male speed skaters of high school in the off-and in-seasons together with 12 untrained age-matched students were evaluated by comparing with the Recommended Dietary Allowance (RDA) for young individuals (15〜17 yr old). Mean intakes of vitamin C (C) by speed skaters (115 mg/day in off-season, 144 mg/day in inseason) and untrained (105 mg/day) were higher than that of RDA level (90 mg/day). Speed skaters had significantly lower C levels in off-season (860 μg/dl) than that of untrained (1110 μg/dl). However, they had higher levels of plasma C (1220 μg/dl) in in-season than in off-season. Although mean intakes of vitamin E (E) by speed skaters in off-season (7 mg/day) and untrained (9 mg/day) were lower than that of RDA (10 mg/day), these subjects had normal levels of plasma E (10.1 μg/ml in speed skaters, 9.4 μg/ml in untraiend; α-tocopherol). In in-season, E intake by speed skaters (12 mg/day) increased above RDA level, whereas plasma E concentration (10.1 μg/ml) maintained at the level in off-season. Mean intakes of vitamin A (A) by both speed skaters and untrained were higher than that of RDA level. All subjects had adequate levels of plasma retinol concentration (0.52〜0.55 μg/ml), whereas speed skaters had remarkably lower levels of plasma β-carotene (0.15 ± 0.07 μg/ml in off-season, 0.10 ± 0.04 μg/ml in in-season) than untrained students (0.52 ± 0.19 μg/ml). These results suggest the possibility that vigorously trained young athletes should take higher levels of antioxidant vitamins C, E and A than respective RDAs for maintaining adequate blood levels of the vitamins.

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