People who are overweight or obese are more likely to have lower circulating levels of vitamin D and may have trouble with conversion to its hormonally active form, a Norwegian study suggests.
These findings, published in the Journal of Nutrition, may partially explain why carrying extra pounds raises risk of several poor health outcomes linked to low vitamin D. The hormonally active form is critical for maintaining cell health, strong bones, a strong immune system, and a healthy heart and brain.
University of Oslo researchers observed almost 1,800 people for six years—about 62 percent obese and 11 percent morbidly obese as indicated by Body Mass Index (BMI)—and found an inverse relationship between higher BMI and serum concentrations of circulating 25(OH)2D and the hormonally active 1,25(OH)2D.
A seasonal variation of both vitamin D metabolites in the obese subjects provided clues that excess weight disturbed the complicated conversion (hydroxylation) of the circulating 25(OH)2D to hormonaly active 1,25(OH)2D in the kidneys.
The authors suggest that measurement of both serum concentrations, 25(OH)2D to 1,25(OH)2D, in overweight and obese persons may be valuable because of “the reduced bioavailability” of the fat-soluble vitamin that “accumulates in excess body fat and muscular tissue.”
The research confirms prior studies’ findings that people who are overweight or obese may need to obtain higher amounts of vitamin D from sun exposure, diet or supplementation. In addition, achieving a healthier BMI is predicted as a way to improve vitamin D status.
Several other factors affect vitamin D status, and include lack of sunlight exposure, skin with higher melanin content (darker skin), older age, low dietary intake, and impaired ability to absorb vitamin D from the diet.
Source: Lagunova Z, Porojnicu AC, Vieth R, Lindberg FA, Hexeberg S and Moan J. Serum 25-Hydroxyvitamin D is a Predictor of Serum 1,25-Dihydroxyvitamin D in Overweight and Obese Patients. J Nutr 2011; 141: 112-117. doi: 10.3945/jn.109.119495.
I found this to be an interesting paper. The point is that one of the big reasons for why obesity leads to poor health is because it wrecks your ability to use a powerful hormone, vitamin D. People overweight need more vitamin D to cope, plus will improve vitamin D status when they lose weight. A big deal.