Calcium and vitamin D status in the adolescent: key roles for bone, body weight, glucose tolerance, and estrogen biosynthesis.

This review paper highlights a number of important public health issues related to calcium and vitamin D status in adolescents. Dietary calcium intake has declined dramatically over the past several decades among adolescents, and inadequate serum vitamin D levels have been documented in up to 54% of teens. A recent trend of decreasing consumption of dairy foods, especially milk, has contributed to this problem. Calcium and vitamin D are critically important for bone mineral accrual during adolescence, and altered calcium homeostasis can impact optimal bone acquisition. Serum and cellular calcium concentrations are controlled, in part, by the actions of vitamin D. Newer research seeks to clarify the potential functions of calcium and vitamin D in the regulation of body weight, glucose tolerance, and ovarian function. Numerous observational studies have noted an inverse association between body weight, percent body fat, and dietary calcium intake; however, clinical trials evaluating the affect of increased calcium on weight loss have been mixed. There is a reduced incidence of insulin resistance syndrome with increasing dairy intake in overweight individuals, and serum 25 hydroxyvitamin D levels are positively correlated with insulin sensitivity. Vitamin D receptor is expressed in all calcium-regulated tissues, including the ovary; thus, calcium and vitamin D appear to be necessary for full ovarian function. This review paper will examine the important role of vitamin D and calcium in the regulation of bone, weight, glucose tolerance, and estrogen biosynthesis.