Lactase deficiency: prevalence in osteoporosis.

We determined the prevalence of lactase deficiency by analysis of respiratory hydrogen (H2) in 30 women with idiopathic postmenopausal osteoporosis and in 31 female control subjects without evidence of metabolic bone disease. Eight subjects with osteoporosis had breath H2 excretion greater than 0.20 ml/minute at 2 h after receiving 50 g of lactose and were considered lactase deficient; only one control subject was lactase deficient (P less than 0.05). Symptoms developed in seven of the nine lactase-deficient persons after receiving 50 g of lactose; in contrast, only three of the 52 lactase-normal subjects had symptoms. Although none of the lactase-deficient subjects was aware of milk intolerance, their intake of both lactose and calcium was significantly lower than that in the lactase-normal group. Lactase deficiency appears to be one of several factors that predispose to the development of osteoporosis, probably through diminished calcium intake and possibly through an effect on calcium absorption.