Haptoglobin, which is encoded by Hp gene, is a hemoglobin-binding protein that has antioxidative properties. This protein has a common polymorphism that consists of two different alleles: Hp1 and Hp2. As haptoglobin phenotypes, Hp1-1, Hp2-1 and Hp2-2 exist. The frequencies of these three haptoglobin phenotypes show marked geographical differences in the world. It has been reported that the haptoglobin phenotypes (genotypes) has a significant effect on vitamin C metabolism in Caucasians and Mongoloids. Serum vitamin C concentration was the lowest in Hp2-2 subjects compared with Hp1-1 and Hp2-1. A lower stability of L-ascorbic acid in blood from Hp2-2 subjects was shown by in vitro experiments. From these studies, it is suggested that individuals with Hp2-2 phenotype has an increased risk of vitamin C deficiency.