Boost your vitamin D levels one pushup at a time
Overweight and obese women who lost significant weight experienced major boost in vitamin D levels
By Ignacio Lobos, Hutchinson Center External Communications Editor
If you are overweight and looking for yet another powerful reason to lose all those extra pounds, data from a new study led by the Hutchinson Center may just tip the scales in favor of exercise and diet: People who lost 15 percent of their body weight gained a significant boost in vitamin D.
The major vitamin D gains among those who lost the most weight came as a surprise to Dr. Anne McTiernan, director of the Prevention Center at the Hutchinson Center and principal investigator of the yearlong study.
Vitamin D has recently become an important topic of research because it’s a key nutrient, and many of us don’t seem to be getting enough of it. Overweight and obese people in particular appear to lack sufficient levels of this vitamin, which promotes calcium absorption, bone growth and bone healing—and protects adults from osteoporosis.
But vitamin D does a lot more. We have learned that cell growth, neuromuscular and immune function, and the reduction of inflammation are influenced by vitamin D. And it plays a role in many gene-encoding proteins that regulate cell proliferation, differentiation and programmed cell death.
We get vitamin D from exposure to the sun—10 minutes a day is enough to trigger adequate amounts—and from some foods, such as fatty fish.
Optimal levels of vitamin D out of reach for the overweight
The optimal circulating range of vitamin D is thought to be between 20 and 50 nanograms per milliliter, or ng/mL, according to a recent data review conducted by the Institute of Medicine, which found that blood levels under 20 ng/mL are inadequate for bone health and levels over 50 ng/mL are associated with potential adverse effects, such as an increased risk of developing kidney stones.
In their study, McTiernan and her colleagues were trying to determine the effect of weight loss on vitamin D. The study recruited 439 overweight-to-obese, sedentary, postmenopausal Seattle-area women, ages 50 to 75, who were randomly assigned to one of four groups:
- Exercise only
- Diet only
- Exercise plus diet
- No intervention
Before the study got under way, about 70 percent of the participants had less-than-optimal levels of vitamin D; 12 percent of the women were at risk of vitamin D deficiency.
Those who lost 5 percent to 10 percent of their body weight—equivalent to approximately 10 to 20 pounds for most of the women in the study—through diet and/or exercise saw a relatively small increase in blood levels of vitamin D (about 2.7 ng/mL).
Women who lost more than 15 percent of their weight experienced a nearly threefold increase in vitamin D (about 7.7 ng/mL), independent of dietary intake of the nutrient.
“It appears that the relationship between weight loss and blood vitamin D is not linear but goes up dramatically with more weight loss. While weight loss of 5 percent to 10 percent is generally recommended to improve risk factors such as blood pressure, cholesterol and blood sugars, our findings suggest that more weight loss might be necessary to meaningfully raise blood vitamin D levels,” McTiernan said.
Researchers don’t know exactly why obese and overweight people have lower levels of vitamin D. But they suspect the nutrient is stored in fat deposits. During weight loss, according to one hypothesis, the vitamin D that is trapped in the fat tissue is released into the blood and available for use throughout the body.
“Vitamin D is found in several different forms in the body and its pathways of action are very complex, so the degree to which vitamin D becomes available to the body as a result of weight loss is not well understood,” said Dr. Caitlin Mason, lead author for the study.
But because “vitamin D is generally lower in persons with obesity, it is possible that low vitamin D could account, in part, for the link between obesity and diseases such as cancer, heart disease and diabetes,” Mason said.
More research needed
This is why continuing to study vitamin D deficiency is important, researchers said.
“More targeted research ongoing at the Hutchinson Center and elsewhere aims to better understand whether vitamin D plays a specific role in the prevention of these chronic diseases,” said McTiernan, who is recruiting Seattle-area obese and overweight postmenopausal women for a separate new study to assess the impact of vitamin D on weight loss and breast cancer risk factors.
The National Institutes of Health, the National Cancer Institute and the Canadian Institutes of Health funded the research. Center authors included Liren Xiao, Carolyn Bain, and Drs. Ikuyo Imayama, Catherine Duggan, Ching-Yun Wang and Marian Neuhouser, all of PHS. The study also included investigators at the University of Washington, the University of Illinois at Chicago, the University of British Columbia, Case Western Reserve University, the University of Minnesota, the National Cancer Institute and Harvard Medical School.