| 10966885 |
Wortsman J, Matsuoka LY, Chen TC, Lu Z, Holick MF: Decreased bioavailability of vitamin D in obesity. Am J Clin Nutr. 2000 Sep;72(3):690-3.
BACKGROUND: Obesity is associated with vitamin D insufficiency and secondary hyperparathyroidism. OBJECTIVE: This study assessed whether obesity alters the cutaneous production of vitamin D (3) (cholecalciferol) or the intestinal absorption of vitamin D (2) (ergocalciferol). DESIGN: Healthy, white, obese [body mass index (BMI; in kg/m (2)) > or = 30] and matched lean control subjects (BMI vitamin D (2) orally. RESULTS: Obese subjects had significantly lower basal 25-hydroxyvitamin D concentrations and higher parathyroid hormone concentrations than did age-matched control subjects. Evaluation of blood vitamin D (3) concentrations 24 h after whole-body irradiation showed that the incremental increase in vitamin D (3) was 57% lower in obese than in nonobese subjects. The content of the vitamin D (3) precursor 7-dehydrocholesterol in the skin of obese and nonobese subjects did not differ significantly between groups nor did its conversion to previtamin D (3) after irradiation in vitro. The obese and nonobese subjects received an oral dose of 50000 IU (1.25 mg) vitamin D (2). BMI was inversely correlated with serum vitamin D (3) concentrations after irradiation (r = -0.55, P: = 0.003) and with peak serum vitamin D (2) concentrations after vitamin D (2) intake (r = -0.56, P: = 0.007). CONCLUSIONS: Obesity-associated vitamin D insufficiency is likely due to the decreased bioavailability of vitamin D (3) from cutaneous and dietary sources because of its deposition in body fat compartments. |
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