Human Genetic Variation Influences Vitamin C Homeostasis by Altering Vitamin C Transport and Antioxidant Enzyme Function

New evidence for the regulation of vitamin C homeostasis has emerged from several studies of human genetic variation. Polymorphisms in the genes encoding sodium-dependent vitamin C transport proteins are strongly associated with plasma ascorbate levels and likely impact tissue cellular vitamin C status. Furthermore, genetic variants of proteins that suppress oxidative stress or detoxify oxidatively damaged biomolecules, i.e., haptoglobin, glutathione-S-transferases, and possibly manganese superoxide dismutase, affect ascorbate levels in the human body. There also is limited evidence for a role of glucose transport proteins. In this review, we examine the extent of the variation in these genes, their impact on vitamin C status, and their potential role in altering chronic disease risk. We conclude that future epidemiological studies should take into account genetic variation in order to successfully determine the role of vitamin C nutriture or supplementation in human vitamin C status and chronic disease risk.