Haptoglobin genotype modifies the association between dietary vitamin C and serum ascorbic acid deficiency

Background Haptoglobin (which is encoded by the Hp gene) is a hemoglobin binding protein that has antioxidant properties and a common polymorphism that consists of 2 structurally different alleles Hp1 and Hp2 The capacity of Hp2 to inhibit oxidation and vitamin C depletion is less than that of Hp1 but the influence on vitamin C requirements remains unknown Objective This study aimed to determine whether the Hp poly morphism modifies the association between dietary vitamin C and serum ascorbic acid deficiency (<11 mu mol/L) Design Nonsmoking men and women (n = 1046) between 20 and 29 y of age participated in the Toronto Nutrigenomics and Health Study Blood samples were collected after the subjects had fasted overnight to determine serum ascorbic acid concentrations by HPLC and for genotyping A 196 item food frequency question nave was used to estimate vitamin C intake Results A gene diet interaction on serum ascorbic acid was ob served (P = 0 02) The overall odds ratio (95% CI) for serum as ascorbic acid deficiency was 2 84 (1 73 4 65) for subjects who did not meet the Recommended Dietary Allowance for vitamin C compared with those who did The corresponding odds ratios were 4 77 (2 36 9 65) for the Hp2-2 genotype and 1 69 (0 80 3 63) for earners of the Hp 1 allele Conclusions Individuals with the Hp2-2 genotype had an in creased risk of deficiency if they did not meet the Recommended Dietary Allowance for vitamin C whereas carriers of the Hp I allele did not The findings suggest that the greater antioxidant capacity of Hp1 might spare serum ascorbic acid Am J Clin Nutr 2010 92 1494-500