Vitamin D, the so-called “sunshine vitamin” was once only considered important for bone health, but recent research suggested the nutrient is important to achieve optimum overall health. Low levels of vitamin D have been increasingly blamed for everything from cancer and heart disease to diabetes.
Since overweight and obese women are at risk for chronic diseases and tend to have less-than-optimal levels of vitamin D, Dr. Caitlin Mason, Ph.D., research fellow at Fred Hutchinson Cancer Research Center wanted to know if heavy menopausal women could increase their vitamin D blood levels with weight loss. It turns out those who lost more than 15 percent of their body weight experienced significant increases in the fat-soluble vitamin.
“Since 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," said Mason, the paper’s lead author, published online in the American Journal of Clinical Nutrition. “Determining whether weight loss helps change vitamin D status is important for understanding potential avenues for disease prevention.”
The year-long study – one of the largest ever conducted to assess the effect of weight loss on vitamin D – involved 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 and no intervention.
According to the National Institutes of Health, vitamin D plays many important roles in the body. It promotes calcium absorption and is needed for bone growth and bone healing. Along with calcium, vitamin D helps protect older adults from osteoporosis and youngsters from rickets (soft bones).
The nutrient also influences cell growth, neuromuscular and immune function, and reduces inflammation. Many gene-encoding proteins that regulate cell proliferation, differentiation, and programmed cell death necessary to prevent cancer are modulated in part by the vitamin.
In the Seattle study, participants who lost 5 to 10 percent of their body weight – equivalent to 10 to 20 pounds for most of the women in the study – through diet and/or exercise saw a relatively small increase in vitamin D blood levels (about 2.7 nanograms per milliliter, or ng/mL), whereas women who lost more than 15 percent of their weight experienced a nearly threefold increase in vitamin D (about 7.7 ng/mL), without adding the vitamin to their diet.
While a weight loss of 5 to 10 percent is generally recommended to improve risk factors such as blood pressure, cholesterol and blood sugars, the study suggested that more weight loss might be necessary to meaningfully raise blood vitamin D levels.
“We were surprised at the effect of weight loss greater than 15 percent on blood vitamin D levels," said senior author Anne McTiernan, M.D., Ph.D., Hutchinson’s Prevention Center director, and the study’s lead investigator. “It appears that the relationship between weight loss and blood vitamin D goes up dramatically with more weight loss.”
It is thought that obese and overweight people have lower levels of vitamin D because the nutrient is stored in fat deposits. During weight loss, it is suspected that vitamin D trapped in the fat tissue is released into the blood and available for use throughout the body.
Vitamin D is naturally found in very few foods and is mainly produced within the body when skin is exposed to sunlight. Recent research published in Archives of Internal Medicine suggested that three-quarters of U.S. teens and adults have a vitamin D deficiency for a variety of reasons. It said that just 10 minutes of sun a day is enough to trigger adequate vitamin D production. The average requirement via diet or supplementation is 400 international units per day for most adults.
Mason cautioned that when it comes to vitamin D supplements, more is not necessarily better. Emerging evidence indicates too much vitamin D can also have serious health consequences so it is important to follow dosing information carefully.
"It is always best to discuss supplementation with your doctor, because circulating levels can vary a lot depending on factors such as age, weight, where you live, and how much time you spend outdoors," Mason said. Vitamin D levels tend to decrease as people age and are generally lower among those with dark skin.
A possible link between vitamin D deficiency and chronic diseases, including cancer and heart disease, has not been well established, according to the Institutes of Medicine. “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,” McTiernan said.
She 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. For more information on this study: http://www.fhcrc.org/science/phs/vida/
Lynette Summerill is an award-winning writer who lives in Scottsdale, Arizona. In addition to writing about cancer-related issues for EmpowHER, her work has been seen in newspapers and magazines around the world.
Sources: “Effects of weight loss on serum vitamin D in postmenopausal women,” Am J Clin Nutr July 2011 ajcn.015552; First published online May 25, 2011. doi:10.3945/ajcn.111.015552
http://www.ajcn.org/content/early/2011/05/19/ajcn.111.015552.abstract?ci
“Dietary Supplement Fact Sheet.” Office of Dietary Supplements, National Institutes of Health. Online: http://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional
“Demographic Differences and Trends of Vitamin D Insufficiency in the US Population,” 1988-2004. Adit A. Ginde; Mark C. Liu; Carlos A. Camargo Jr; Archives of Internal Medicine, Mar 2009; 169: 626-632. http://archinte.ama-assn.org/
Dietary Reference Intakes for Calcium and Vitamin D, Institute of Medicine Report Brief, 11/30/2010, published online: http://www.iom.edu/Reports/2010/Dietary-Reference-Intakes-for-Calcium-and-Vitamin-D/Report-Brief.aspx
Reviewed May 26,2011
Edited by Alison Stanton