Use of calcium and vitamin D supplements in women who are postmenopausal may reduce the risk of death from cancer, but they may also increase risk of death from cardiovascular disease.

That’s according to research published today in the journal Annals of Internal Medicine, which reports that women who took calcium and vitamin D supplements had a 7% lower risk of death from cancer but a 6% higher risk of death from cardiovascular disease.

“Our study also found an 11% lower risk for total cancer, including 31% and 19% lower incidences of colorectal cancer and invasive breast cancer,” the study authors wrote.

To reach their findings, the researchers from the University of Arizona conducted a follow-up analysis to the largest ever randomized trial of calcium and vitamin D supplementation, which examined the health outcomes of those supplements on more than 36,000 postmenopausal women.

However, the study authors note that due to the way the study was undertaken, the results should be interpreted carefully.

“Given the study design, we could not disentangle the added benefit or harms of supplementation with calcium and vitamin D in combination versus vitamin D alone, a topic worthy of future study,” they wrote.

Previous observational studies have indicated that those who take calcium supplements have a greater risk of cardiovascular disease-related events than those who don’t take calcium supplements. Low levels of estrogen seen in menopause can also raise the risk of heart disease and stroke.

The risk of cardiovascular disease events is particularly significant for those who consume more than 1,400mg of calcium a day. For women aged over 50, the recommended daily intake of calcium is 1,200mg a day.

During menopause, a decrease in the production of estrogen reduces the absorption of calcium and increases urinary calcium loss. After menopause, women lose roughly 1%  of their bone mineral density each year. As a result, 30% of postmenopausal women in the United States have osteoporosis and of these at least 40% will experience at least one fracture that occurs due to a minor trauma such as a fall.

The Arizona research builds on previous research that indicates a potential connection between vitamin D levels and reduced risk of cancer.

Past researchbhas found a 17% lower cancer mortality among men and women with prostate, lung, colorectal, and ovarian cancers and higher concentrations of vitamin D.

“Our findings that effects on cancer end points seem more prominent among those without prior calcium and vitamin D supplementation suggest that calcium and vitamin D supplementation may affect cancer biology primarily in the setting of augmenting an insufficiency in nutrient status,” the authors of the new study wrote.

Experts say the best thing women can do to stay healthy during and after menopause is to be active, quit smoking, have a healthy diet, and discuss whether supplements are appropriate with a healthcare provider.

Sources:

 Cynthia A. Thomson, PhD, RD, Aaron K. Aragaki, MS, Ross L. Prentice, PhD, Marcia L. Stefanick, PhD, JoAnn E. Manson, MD, MPH, DrPH, Jean Wactawski-Wende, PhD, Nelson B. Watts, MD. Long-Term Effect of Randomization to Calcium and Vitamin D Supplementation on Health in Older Women: Postintervention Follow-up of a Randomized Clinical Trial. Annals of Internal Medicin, 2024. DOI: https://doi.org/10.7326/M23-2598

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