Mixed Results From Vitamin D and Weight Loss Study

Vitamin D3 supplements increased weight loss in dieters who were deficient in the vitamin

/ Author:  / Reviewed by: Joseph V. Madia, MD Beth Bolt, RPh

(RxWiki News) Many women gain weight after menopause. What if a simple vitamin supplement could assist in their weight loss efforts?

Low blood levels of vitamin D have been associated with insulin resistance and chronic inflammation, both conditions that can increase the risk of obesity. Researchers recently conducted a study to see if raising vitamin D levels by taking vitamin D3 pills would help dieters lose weight.

The research team found that adding vitamin D3 to a diet program did not increase weight loss in a group of post-menopausal women. In women who started the program with low blood levels of vitamin D, however, increasing vitamin D to normal levels helped them lose weight.

"Check with your doctor before taking vitamins or other supplements."

Anne McTiernan, MD, PhD, from the Division of Public Health Sciences at the Fred Hutchinson Cancer Research Center in Seattle, Washington, led this research team.

This study included 218 post-menopausal overweight and obese women. Their ages ranged from 50 to 75 years old.

The women were split into two groups: one group took 2,000 IU of vitamin D3 daily and the other group took a fake (placebo) pill. They took the pills for 12 months and were put on a diet and exercise program.

Diets were personalized to contain 1,200 to 2,000 calories, based on a woman’s starting weight. The goal was for the women to lose 10 percent of their weight in six months and to maintain that weight loss for up to a year.

Blood tests were done at the start of the study and 12 months later to measure vitamin D, insulin and C-reactive protein (CRP) in the blood. CRP is a measure of chronic inflammation in the body. Both increased insulin and CRP levels in the blood have been associated with obesity.

After 12 months, the researchers found no difference in the amount of weight loss in the group of women who took vitamin D3 supplements compared to the women who took placebos.

Some women started the study with low blood levels of vitamin D. These levels were lower than 32 ng/mL. The women in this group who took vitamin D3 and brought their blood levels up to at least 32 ng/mL lost almost 10 percent of their weight on the diet program.

Women who remained at low blood levels of vitamin D despite taking supplements only lost 6.6 percent of their body weight. These women also had larger waistline measurements than the women whose blood levels of vitamin D were raised to 32 ng/mL.

The researchers noted that some women did not take all their pills. In the women who did take all their pills, CRP decreased by 46 percent in the women who took vitamin D3, compared with 25 percent in the placebo group.

Limitations of the study included the fact that women with vitamin D blood levels lower than 10 ng/mL were not included in the study, so effects of giving vitamin D3 to this set of women was not evaluated by the study. Additionally, only one dose of vitamin D3 was tested in this study.

None of the study participants reported any adverse reactions.

The study's authors wrote that it wasn’t clear whether low blood levels of vitamin D in the women caused their obesity or if obesity caused low vitamin D levels.

“Whether higher doses of vitamin D would yield significant effects, or whether significant effects would be evident among women with more severe vitamin D deficiency (eg, < 10 ng/mL) will need to be examined in future studies,” the authors stated.

This research was published in the May issue of the American Journal of Clinical Nutrition.

Funding for the research was provided by the Susan G. Komen for the Cure Scientific Advisory Council, the National Cancer Institute and the Breast Cancer Research Foundation.

The authors declared no conflicts of interest.

Review Date: 
April 30, 2014
Last Updated:
May 1, 2014