(CNN) -- Older women who don't get enough vitamin D may be slightly heavier than those who do.
A Kaiser Permanente study, published online in the recent issue of the Journal of Women's Health, looked at more than 4,600 women aged 65 and older for a four and one-half year period. Researchers found women with low levels of vitamin D in their blood gained about two pounds more than those with adequate levels of the vitamin.
So what's the big deal, you ask?
"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," said study author Dr. Erin LeBlanc, an endocrinologist and researcher at the Kaiser Permanente Center for Health Research in Portland, Oregon.
Called the "sunshine vitamin" because most of us get it from the sun, vitamin D helps maintain our bones and muscles, and keeps our central nervous system in check. But if you take too much it could be toxic, causing nausea, vomiting and loss of appetite.
Although the sun's rays are the primary source, vitamin D can also be found in milk products, fatty fish and fortified items such as cereals and juices. But even with all these sources, prior research has found that women, especially older women, aren't getting enough.
In the Kaiser study, researchers found almost 80% of participants had insufficient levels of vitamin D. Because the vitamin's main source is sunlight, the investigators say those women lacking vitamin D may not spend enough time outdoors. They may also have a poor diet.
LeBlanc points out that this study was conducted among older women who, for the most part, were not trying to lose weight - though some of them did so as a natural result of aging. About 60% of the women in the study remained at a stable weight during the study period, 27% lost more than 5% of their body weight, and 12% gained more than 5% of their body weight.
"Our study only shows an association between insufficient levels of vitamin D and weight gain, we would need to do more studies before recommending the supplements to keep people from gaining weight," LeBlanc said. "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."