Vitamin D could matter in older women’s weight gain

We mostly get our vitamin D by exposure to the sun, and these days, who just goes out in the sun? So there’s been a lot of attention given to — and confusion over — vitamin D supplements, something many doctors recommend.

Now there’s a new study a possible vitamin D benefit: In a group of women older than 65 who had gained weight over 4½ years, those whose levels of the vitamin were low had gained a little more weight, researchers found in a study published Monday.

The study adds to the conversation about vitamin D, but the researchers say more study is needed about any possible connection between weight and vitamin D.

“This is one of the first studies to show that women with low levels of vitamin D gain more weight, and although it was only 2 pounds, over time that can add up,” said Erin LeBlanc, the author of the study and an endocrinologist and researcher at the Kaiser Permanente Center for Health Research in Portland, Ore.

LeBlanc’s study was published online in the Journal of Women’s Health.

A second study about vitamin D was published Monday and perhaps adds to the confusion over what people ought to do. A Loyola University Chicago School of Medicine study of two new tests for vitamin D found they are often inaccurate.

Last year, the U.S. Centers for Disease Control and Prevention concluded that vitamin D levels in most Americans are adequate.

The Oregon study looked at 4,659 women over 4½ years. Of the women who lost weight or maintained a stable weight, the researchers said there was no association with vitamin D levels.

But among the 571 women who gained more than 5% of their body weight, low vitamin D levels seemed to make a difference.

“We would need to do more studies before recommending the supplements to keep people from gaining weight,” LeBlanc said in a statement. “Since there are so many conflicting recommendations about taking vitamin D for any reason, it’s best if patients get advice from their own healthcare provider.”

Evolution and history may be somewhat to blame.

The researchers noted that it’s possible that decreased sun exposure in fall and winter could trigger the body to increase fat storage for the winter. “As modern societies move indoors, we propose that decreased sunlight exposure leads to chronic [vitamin D] insufficiency and subsequent weight gain year round (not just seasonally),” they wrote.

In the vitamin D tests study, the researchers looked at two tests approved by the federal Food and Drug Administration and how they did with 163 random blood samples. In 40% of one and 48% of the other test, the results were at least 25% too high or too low, they said in their study presented at an annual meeting in Houston called ENDO.

Vitamin D tests are among the most frequently ordered tests.