Calcium, Vitamin D Lower Insulin Secretion

BOSTON—A recent study at the Harvard School of Public Health, Boston, found calcium intake or systemic vitamin D status, after adjustment for intake of dairy products, was associated with decreased insulin secretion (J Nutr. 2009;139(3):547-54). Researchers examined intakes of total calcium and vitamin D, and plasma concentrations of 25 hydroxyvitamin D [25(OH)D] in relation to fasting plasma concentrations of C-peptide in two cross-sectional studies among healthy men from the Health Professionals Follow-up Study and among healthy women from the Nurses' Health Study I. Intake of total calcium was modestly inversely associated with C-peptide concentration in women; however, the inverse association was not significant in men. Concentrations of C-peptide were 20 percent lower among men who had plasma concentrations of 25(OH)D in the highest quartile compared with those in the lowest quartile; there was no association in women. The inverse association between calcium intake and the plasma C-peptide concentration was stronger in hypertensive individuals of both sexes. The difference in the C-peptide concentrations between extreme quartiles of calcium intake was 17 percent in men and 20 percent in women. Plasma concentrations of C-peptide for the combination of the highest tertiles of calcium intake and plasma 25(OH)D compared with the opposite extreme were 35 percent lower in men and 12 percent lower in women.