Lactase Gene C/T−13910 Polymorphism, Calcium Intake, and pQCT Bone Traits in Finnish Adults

Genetic lactase nonpersistence may influence calcium intake and thereby bone health. We investigated in the Cardiovascular Risk in Young Finn Study whether young adults aged 31–46 years with the C/C −13910 genotype are more susceptible to reduced bone phenotypes, low-energy fractures, and low calcium intake than subjects with other lactase genotypes. We also analyzed the gene–environment interactions on bone with calcium intake and physical activity. Peripheral quantitative computed tomography bone traits were measured from the distal and shaft sites of the radius and tibia. The total number of those subjects whose nondominant forearm was measured and the lactase genotype was defined was 1551. Information on diet, lifestyle factors, and fractures was collected with questionnaires. The mean intake of calcium was the lowest in men with the C/C −13910 genotype ( P = 0.001). Men with the T/T −13910 genotype had ~3% higher trabecular density at the distal radius and distal tibia compared to other lactase genotypes ( P = 0.03 and 0.02, respectively). In women, we found no evidence of the gene effect at the radius and tibia. No major interactions of the C/T −13910 polymorphism with calcium intake or physical activity on bone phenotypes were found in either sex. In conclusion, the C/T −13910 polymorphism was associated with trabecular density at the distal radius and tibia in men. These differences may be due to the differences in calcium intake between the lactase genotypes.