TUESDAY, June 26, 2012 (HealthDay News) -- Older women with low levels of vitamin D, also known as the "sunshine vitamin," may be more likely to gain weight, a new study indicates.
Researchers from the Kaiser Permanente Center for Health Research in Portland, Ore., said their findings are significant since most women aged 65 and older do not have enough vitamin D in their blood.
The researchers followed more than 4,600 women aged 65 and older over the course of nearly five years. The study found the women with low levels of vitamin D gained about two more pounds during that time than those with normal levels of the vitamin.
Although most of the women in the study were not trying to lose weight, over the course of the study 27 percent of the women lost more than 5 percent of their body weight and 12 percent gained more than 5 percent of their body weight, the researchers noted.
Low levels of vitamin D were found in 78 percent of the women. These women generally weighed several pounds more to begin with, the researchers noted. In the group of women that did gain weight, those with insufficient vitamin D levels gained 18.5 pounds over five years. In comparison, the women with normal vitamin D levels gained 16.4 pounds during that time frame.
"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 two pounds, over time that can add up," study author Dr. Erin LeBlanc, an endocrinologist and researcher at the Kaiser Permanente Center for Health Research in Oregon, said in a Kaiser Permanente news release.
"Nearly 80 percent of women in our study had insufficient levels of vitamin D," LeBlanc said. "A primary source of this important vitamin is sunlight, and as modern societies move indoors, continuous vitamin D insufficiency may be contributing to chronic weight gain."
The study authors pointed out that previous research found that older women may need higher doses of vitamin D to keep their bones strong and prevent fractures, although there is not enough evidence to support vitamin D supplements among younger people. They noted, however, that other experts say many adults require these supplements to improve their bone health.
"Our study only shows an association between insufficient levels of vitamin D and weight gain," LeBlanc said. "We would need to do more studies before recommending the supplements to keep people from gaining weight. Since there are so many conflicting recommendations about taking vitamin D for any reason, it's best if patients get advice from their own health care provider."
The study, funded by the U.S. National Institutes of Health, was published online June 25 in the Journal of Women's Health.
The U.S. National Institutes of Health Office of Dietary Supplements provides more information on vitamin D.