Lactase persistence may explain the paradoxical findings of high vitamin D concentrations in Europeans living in areas of low UV-B irradiation.

Abstract

Vitamin D has a critical role in skeletal health and maintaining serum calcium levels. Calcium is needed for a variety of cellular and metabolic processes in the body. Large amounts of vitamin D can be produced in the skin when exposed to UV-B radiation. It is therefore a paradox that in Europe, Caucasians living in higher latitude countries, such as Scandinavia and Iceland, have higher serum vitamin D compared with those living in lower latitude. In a recent study of adult-type lactase persistence (LP), it was shown that Caucasian of European descent, who carried the C-13910T LP allele, had higher levels of total serum 25-hydroxyvitamin D compared with those who were lactase non-persistent. This was attributed to higher consumption of dairy. We postulated that the distribution of the LP C-13910T allele in Caucasian populations may explain the vitamin D concentration pattern seen in Europe. Baseline mean total serum 25 hydroxyvitamin D concentration from a clinical trial of post-menopausal women with osteoporosis was correlated to published LP frequencies in European populations. In multiple regression analysis, mean total serum 25 hydroxyvitamin D concentrations in both winter and summer were in turn correlated to LP phenotype frequency (winter: r2 = 0.51, p < 0.05; summer: r2 = 0.4, p < 0.05). High frequency of LP in northern Europe may explain high mean total serum 25 hydroxyvitamin D concentrations despite low UV-B radiation exposure.