Objective: To assess the prevalence of vitamin D deficiency in healthy postmenopausal women with normal sun exposure but without vitamin D fortification in their diets.
Design: We studied 90 healthy ambulatory women who were residents of Santiago, Chile (latitude 33 degrees S); 30 were premenopausal (32.6 +/- 7.4 y), and 60 were postmenopausal (63.7 +/- 9.7 y). Half of the women were studied during the winter and the other half during the following summer. Each provided a fasting blood sample to measure biochemical parameters, parathyroid hormone, and 25-hydroxyvitamin D and completed a questionnaire to estimate sunlight exposure. A first morning urine sample was collected in postmenopausal women to measure deoxypyridinoline. Various cutoff points of 25-hydroxyvitamin D were used to assess the prevalence of vitamin D deficiency (<9, <15, and <20 ng/mL).
Results: All of the women had normal renal and liver parameters. Sunlight exposure was adequate in almost all of the volunteers (93% in both groups, P > 0.05). In postmenopausal women, serum 25-hydroxyvitamin D was less than 9 ng/mL in 12%, less than 15 ng/mL in 40%, and less than 20 ng/mL in 60%, compared with 0%, 13%, and 27%, respectively, in premenopausal women. Deoxypyridinoline was 75% higher during winter than summer (9.8 +/- 2.5 vs 5.6 +/- 1.4 nmol/mmol creatinine, P < 0.0001).
Conclusions: Vitamin D deficiency is very common in Chilean healthy postmenopausal women with normal sun exposure but without vitamin D fortification in their diets. This finding is associated with higher bone resorption during winter time and emphasizes the need to increase vitamin D intake in healthy postmenopausal women.