We provided a low-vitamin C (C) diet to 17 healthy females ( age, 21.0±1.1 y ) for three days before the experimental day and the orally administered 1 mmol ascorbic acid crystal ( 1 mmol 176 mg ) or dehydroascorbic acid ( 1 mmol 174 mg ). Then we measured the total amount of C in urine and blood samples. This metabolism test was conducted by the crossover method. The wash out period was put to be a month.At 24h after administration of 1 mmol of VC, total VC excretion ( 46.7±18.1 mg ) by AA homozygotes of GTSP 1 was greater ( p ＜0.0069 ) than that ( 28.2 ± 14.0 mg ) by GA heterozygotes. One hour after administration of VC, blood total VC levels were also significantly different ( p ＜0.0036 ) between the homozygotes and heterozygotes. The effects of other polymorphisms in xenobiotic enzymes on VC metabolism were small.