Vitamin D and its effect on weight loss examined in new study

A new study published online April 18 in the American Journal of Clinical Nutrition suggests that healthy or “replete” levels of vitamin D may be associated with weight loss in a certain segment of postmenopausal overweight women.

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Scientists at Fred Hutchinson Cancer Research Center looked at the results of Vitamin D supplementation on a group of overweight women ages 50 to 75 who tested low in D. The research was conducted as part of the Vitamin D, Diet and Activity study at the Hutch.

Vitamin D has multiple physiologic functions beyond its classically recognized role in calcium homeostasis and bone metabolism. Vitamin D receptors are found in more than 30 cell types and the focus has recently switched from bone health to vitamin D’s effect on cancer, cardiovascular health, and other areas, such as weight loss.

“Vitamin D is certainly having its day in the spotlight,” said Dr. Caitlin Mason, researcher at the Hutch’s Public Health Sciences who worked on the vitamin D and weight loss study. “But we still have a lot to understand.”

 The study compared 12 months of oral vitamin D supplementation (2000 IU/d) compared with placebo on changes in weight, body composition, and metabolic markers [insulin and C-reactive protein (CRP)] during a structured behavioral weight-loss program in overweight and obese postmenopausal women.

Women who took vitamin D in addition to participating in a diet and exercise weight loss program lost similar amounts of weight to those who just completed the weight loss program. There were also no significant differences in the reduction in weight corrected for height, waist circumference, percentage body fat, trunk fat, insulin or C-reactive protein.

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However, women randomly assigned to vitamin D supplementation who became replete [i.e., whose blood levels of 25(OH)D rose to 32 ng/mL or greater] lost more weight and had greater improvements in body composition compared with women who did not become replete. These finding suggest a potential threshold effect and highlights the importance of considering changes in nutrient status rather than only the average magnitude of change.

The women whose D levels became replete lost an average of 19 pounds over the course of 12 months as compared to the women in the placebo group, who lost an average of 12 pounds during the same time period. Both groups participated in a reduced calorie diet and an exercise program that included approximately 45 minutes of moderate-to-vigorous aerobic activity a day, five days per week.

“This suggests women trying to lose weight might want to have their D levels checked by their provider and replenish their vitamin D levels either through supplements or sun and then have their D levels rechecked after a few months to make sure they’ve risen to a healthy level,” said Anne McTiernan, M.D., Ph.D., principal investigator of the study and a Member of the Fred Hutch Cancer Research Center’s Public Health Sciences Division.

While the NIH lists anything over 50 ng/mL as too high, others in the scientific community consider anything between 30 ng/mL and 80 ng/mL as normal.  In the weight loss study, women were considered replete at around 32 ng/mL.

The report also demonstrated that women who took their vitamin D pills regularly showed a drop in C-reactive protein, a marker of inflammation. If vitamin D can modify the metabolic alterations associated with obesity, then changes in circulating concentrations of vitamin D could modify obesity-disease relations.

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“An overweight person’s body is in a state of chronic inflammation and all of these inflammation proteins that the body produces can cause things like elevated risk for cancer and diabetes,” said Catherine Duggan, Ph.D., principal staff scientist with the Fred Hutch Cancer Research Center’s Public Health Sciences Division. “Vitamin D helped with that. It could make the condition of being overweight less stressful on the body.”

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