Effects of Weight Loss on Vitamin D Levels in Postmenopausal Women

Scientific evidence shows that low levels of vitamin D in blood are associated with obesity. This may explain why obese individuals are at a higher risk of acquiring heart diseases and cancers. This study attempted to investigate whether weight loss in elderly women, who had attained menopause, could lead to higher levels of vitamin D in the blood. The results obtained in this study show that higher concentrations of vitamin D in blood could be achieved though weight loss accomplished by exercise and/or decreased calorie consumption.

It is well known that being overweight and obese places an individual at a higher risk of heart disease and cancer. The reason for such an association is not yet known. Some authors speculate that lower levels of vitamin D in the blood, as found in most obese individuals, may account for the heightened risk of other cardiovascular diseases and cancers. Other studies have also suggested that administering vitamin D supplements to those who are obese and overweight may help them in losing weight. However, these studies are limited and not concrete. No studies have been conducted yet to investigate whether the level of vitamin D in the blood could be raised by weight loss. Because of the rising incidence of obesity and its associated risk factors, this study sought to explore the association between weight loss and vitamin D.

* For this study, 439 women, who were obese and had attained menopause, were selected.
* The women were divided into four groups. Group 1 (118 women) was asked to follow certain changes in the diet. Group 2 (117 women) was given exercise regimens and group 3 (117 women) was subjected to both diet control and exercise. Group 4 (87 women) was the control group, without any dietary changes or exercise regimens.
* Diet change targeted a 10 percent weight loss. The exercise regimen for Groups 2 and 3 involved aerobic exercises for 45-minutes for five days every week.
* For all women, the level of vitamin D in the blood was measured at the beginning and the end of one year, during which they underwent their dietary and exercise regimens.

Results/Key findings
* The results showed that the higher the percentage of weight loss, the greater the increase in vitamin D in the blood. For example, women who lost 10 to 14.9 percent of their weight had an average increase of 3.3 ng/ml of vitamin D in the blood.
* The results also showed that initial vitamin D levels in the blood did not influence the final effect of the weight loss regimen on vitamin D at the end of the study period.
* The increase in vitamin D concentrations depended on the magnitude of fat loss.

Next steps/Shortcomings
The authors of this study agree that their sample did not have a significant representation from Hispanic and non-white women. They speculate that the results of this study may have been different in non-white women. They suggest further studies that include larger populations of other races, to understand the underlying mechanisms of differences in Vitamin D metabolism and their link with heart disease and cancer. They also add that since vitamin D is formed in the body with the help of sun exposure, it should have been considered in this study.  All these factors will have to be taken into account for future research.

Vitamin D has complex metabolic pathways and functions as a hormone in the body. Deficiency of this vitamin is linked with obesity and deposition of fat in the body. This study shows that higher levels of weight loss in obese post menopausal women is linked to rising levels of vitamin D, over a study period of 12 months. This study also reveals that initial levels of vitamin D in the blood had sparse effect on the women being able to lose weight by the end of the study. The authors suggest further studies on larger samples of a more general population, to find out the optimum level of vitamin D in the blood and how it can be achieved in order to maintain good health.

For More Information:
Effects of Weight Loss on Serum Vitamin D in Postmenopausal Women
Journal Publication: American Journal of Clinical Nutrition, May 2011
By Caitlin Mason; Liren Xiao
From the Fred Hutchinson Cancer Research Center, Seattle, Washington

*FYI Living Lab Reports Are Summaries of the Original Research.

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