doreen T
Sat, Nov-18-00, 17:29
Obesity Reduces Availability of Vitamin D From Sunlight
Wortsman et al. assessed whether the cutaneous production of vitamin D3, and/or the intestinal absorption of vitamin D2 is affected by obesity. Thirty-eight healthy white subjects, half of them lean and half obese, were exposed to whole-body irradiation in a phototherapy unit. After irradiation both groups had the same initial rise in levels of the precursor vitamin D3, but in the obese subjects subsequent serum vitamin D concentrations were less than half those of the lean individuals. The subjects were challenged with an oral dose of 50 000 IU of vitamin D2 one month later, and subsequent blood sampling showed serum concentrations of vitamin D were not significantly different between the two groups. In vitro studies on skin cells procured during surgery from obese and nonobese subjects showed that skin samples from obese and nonobese subjects were equally proficient in the production of vitamin D3 when exposed to sunlight. The authors hypothesize that the oral form, vitamin D2, was more bioavailable to the obese because it was deposited directly in the bloodstream. By contrast, increasing subcutaneous body fat may sequester vitamin D3 synthesized in the skin by irradiation.
Wortsman, Jacobo et al. Decreased bioavailability of vitamin D in obesity. Am J Clin Nut 2000;72:690-3.
Wortsman et al. assessed whether the cutaneous production of vitamin D3, and/or the intestinal absorption of vitamin D2 is affected by obesity. Thirty-eight healthy white subjects, half of them lean and half obese, were exposed to whole-body irradiation in a phototherapy unit. After irradiation both groups had the same initial rise in levels of the precursor vitamin D3, but in the obese subjects subsequent serum vitamin D concentrations were less than half those of the lean individuals. The subjects were challenged with an oral dose of 50 000 IU of vitamin D2 one month later, and subsequent blood sampling showed serum concentrations of vitamin D were not significantly different between the two groups. In vitro studies on skin cells procured during surgery from obese and nonobese subjects showed that skin samples from obese and nonobese subjects were equally proficient in the production of vitamin D3 when exposed to sunlight. The authors hypothesize that the oral form, vitamin D2, was more bioavailable to the obese because it was deposited directly in the bloodstream. By contrast, increasing subcutaneous body fat may sequester vitamin D3 synthesized in the skin by irradiation.
Wortsman, Jacobo et al. Decreased bioavailability of vitamin D in obesity. Am J Clin Nut 2000;72:690-3.