Calcium and Vitamin D Supplements May Lower Cancer Risk, but Increase Heart Disease Risk
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An analysis from the landmark Women’s Health Initiative trial found that taking calcium and vitamin D supplements lowered a woman’s long-term risk of dying from cancer by 7 percent, but increased the risk of death due to heart disease by 6 percent.
The Women’s Health Initiative — the largest-ever randomized trial on the effects of taking calcium and vitamin D supplements, involving over 36,000 postmenopausal women — originally examined outcomes like fracture risk, cancer, and heart disease. The results were “largely null,” according to the authors.
To explore if those findings changed after more than 20 years, authors used available data on health events and death rates to update the original findings.
“The findings demonstrate the importance of longer-term research,” says lead author Cynthia Thomson, PhD, RD, a professor and the director of the Zuckerman Family Center for Prevention and Health Promotion at the College of Public Health at the University of Arizona in Tucson.
Generally studies are funded for five-year cycles, but cancer can sometimes take decades to develop, she points out.
How Much Calcium and Vitamin D Do Experts Recommend?
The current recommendation for calcium intake for the general population (males and premenopausal females) is 1000 milligrams (mg) daily including diet and supplements, says Marilyn Tan, MD, an associate professor of medicine, internal medicine doctor, and endocrinologist at Stanford Health Care in California, who was not involved in the study. “For postmenopausal females, the goal is 1,200 mg calcium daily in diet and supplements. Excessive calcium has risks, including kidney stones, gastrointestinal symptoms, and high blood calcium,” says Dr. Tan.
Getting enough vitamin D is important for many bodily functions including immunity and glucose metabolism. It also supports bone health by helping the body absorb calcium. Vitamin D is normally made in the skin after exposure to sunlight.
Experts recommend 600 international units (IU) for people 1 to 70 years old, and males over 70 years of age and postmenopausal women should consume at least 800 (IUs) of vitamin D per day.
Study Findings Come With Caveats
The findings should be interpreted with caution because of the multiple conditions that were looked at in the study, and so some of the findings could be due to chance, the authors noted. The lack of diversity in participants (subjects were mostly white and highly educated) is another limitation of the study, they wrote.
Because there has been significant interest in vitamin D, other studies have previously suggested reduced cancer incidence with vitamin D supplementation, but the findings on calcium are more unique, says Tan. “This study suggests a possible delayed effect of calcium plus vitamin D supplementation,” she says.
What’s the Bottom Line on Taking Calcium Plus Vitamin D Supplements?
Based on this study, it’s difficult to tease out the individual effects of calcium versus vitamin D, says Tan.
For bone health, the recommendations for the calcium intake goals are unchanged, she says. “That said, for patients where heart disease risk is a concern, I generally recommend dietary sources of calcium over calcium supplements,” she says.
This research, coupled with earlier studies on vitamin D, suggests that the bottom line message to postmenopausal women is to aim to get the recommended daily allowance of calcium through diet and potentially take a vitamin D supplement if they’re deficient, says Stephanie Faubion, MD, director of the Mayo Clinic Center for Women’s Health in Jacksonville, Florida, and medical director of the Menopause Society, who was not involved in this study.
If you’re currently taking a vitamin D plus calcium supplement and you’re not sure about your risk of heart disease, consult your healthcare provider, says Tan.
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