OAKLAND, Calif., May 14, 2007 /PRNewswire via COMTEX/ -- Postmenopausal women who take calcium and vitamin D supplements may gain less weight than those who do not, although the overall effect is small, according to a report authored by a Kaiser Permanente research scientist and featured in the May 14, 2007 edition of Archives of Internal Medicine.
The study included 36,282 postmenopausal women ages 50 to 79 years who were enrolled in the Women's Health Initiative clinical trial. It found that those who took daily calcium and vitamin D supplements over a seven-year period weighed an average 0.28 pounds less, and were less likely to gain weight than women who received placebos.
The greatest benefits were seen in women who began the study with inadequate calcium intakes -- those consuming less than the current recommendation of 1,200 mg of calcium per day. These women were found to be 11 percent less likely to experience small weight gains (2.2 to 6.6 pounds) after three years, and 11 percent less likely to gain more moderate amounts of weight (more than 6.6 pounds).
"While this study shows that calcium and vitamin D supplements appear to have some small benefits when it comes to controlling weight, women clearly should continue practicing the basic tenets of weight management -- that is monitoring calories in their diets and getting at least 30 minutes of physical activity a day," said lead author Bette Caan, DrPH, a senior epidemiologist at Kaiser Permanente's Division of Research in Oakland, Calif. "Further research may be warranted to address the effect of calcium and vitamin D supplementation combined with caloric restriction and physical activity on weight gain prevention."
According to the Centers for Disease Control and Prevention, the percentage of women ages 50 to 79 who are obese increased by nearly 50 percent in the 1990s.
Dr. Caan noted that age-related changes in body composition, metabolic factors and hormone levels, combined with declines in physical activity, are all factors that can contribute to weight gain and obesity as women age.
"We know that preventing weight gain is likely to have significant health benefits for middle-aged women, so early to middle menopause may be a critical period for women to effectively manage their weight," she said.
Previous studies have shown some evidence that calcium and vitamin D supplements, as well as foods rich in these nutrients, may play a role in effective weight management. One explanation is that calcium and vitamin D work together to regulate metabolism. In addition, calcium may help decrease fatty acid absorption in the intestine.
Dr. Caan said the latest study findings do not justify altering current dietary recommendations, and that postmenopausal women should continue to be advised to consume 1,200 mg a day of calcium as recommended by the Food and Nutrition Board of the National Academy of Sciences.
Study participants were already enrolled in the dietary modification and/or hormone therapy arms of the Women's Health Initiative (WHI), a long- term clinical trial launched in 1991 by the National Institutes of Health to address the most common causes of death, disability and impaired quality of life in postmenopausal women.
Women were randomized at their first or second year annual visit to receive a dose of 1,000 mg of calcium plus 400 international units (IU) of vitamin D supplements or placebo in a study initially designed to test whether these supplements would reduce the incidence of hip fractures and colorectal cancer. That study found that the supplements slowed loss of bone density over a seven-year period, but were associated with non-significant lower rates of hip fractures, and were not found to be effective in preventing colorectal cancer in healthy postmenopausal women.
The latest study is believed to be the largest double-blind, placebo- controlled clinical trial to report the effects of calcium and vitamin D supplementation on weight change. It was funded by the National Heart, Lung, and Blood Institute (NHLBI) of the National Institutes of Health.
The Kaiser Permanente Division of Research conducts, publishes, and disseminates epidemiologic and health services research to improve the health and medical care of Kaiser Permanente members and the society at large. It seeks to understand the determinants of illness and well being and to improve the quality and cost-effectiveness of health care. Currently, the center's 400-plus staff is working on more than 250 epidemiological and health services research projects.