Study: Taking Calcium and Vitamin D Together May Reduce the Risk of Dying From Cancer, but Raise Mortality Risk for Heart Disease

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• Calcium and vitamin D supplements are often recommended to postmenopausal women to reduce the risk of osteoporosis.

• But new research shows the combination of supplements may raise the risk of dying from heart disease and lower the risk of dying from cancer.

• Experts say it’s important to speak with a healthcare provider before taking the supplements, particularly if you have a higher risk for heart disease or other conditions.

New research suggests that taking calcium and vitamin D supplements together may be both beneficial and risky for postmenopausal women.

The study, published in the Annals of Internal Medicine, found that while women who took both supplements at the same time decreased their risk of dying from cancer, they also increased their chances of death due to cardiovascular disease.

According to Holly Thacker, MD, an internist at Cleveland Clinic who specializes in menopause and women’s health conditions, postmenopausal women have a high risk of developing osteoporosis because bones lose density when estrogen drops during this time. Osteoporosis has been linked with low calcium levels, and vitamin D helps with calcium absorption, so many postmenopausal women take both supplements.

However, experts said the study highlights the need to discuss specific circumstances with a healthcare provider before taking supplements.

“I think what we are starting to appreciate is that more is not always better,” Anuradha Lala-Trindade, MD, a cardiologist at Mount Sinai, told Health. “Supplementation should be warranted and individualized based on baseline risk and potential for benefit.”

Here, experts explain how calcium and vitamin D supplements could affect postmenopausal women and what to consider before taking them.

Linking Calcium and Vitamin D to Disease Risk

For the study, researchers analyzed records from more than 36,000 postmenopausal women enrolled in the Women’s Health Initiative, a program funded by the U.S. Department of Health and Human Services that's been running since 1992.

For about seven years, roughly half of the participants took 1,000 milligrams (mg) of calcium carbonate (which included 400 mg of elemental calcium) and 400 international units (IU) of vitamin D3, a form of vitamin D that humans produce naturally. The rest took a placebo.

The study ended in 2005, and researchers then tracked the participants until December 2020.

The team found that the participants in the supplement group had a 7% lower risk of dying from cancer than the placebo group. However, they had a 6% higher chance of dying from cardiovascular disease than people who didn’t take calcium and vitamin D.

Researchers noted that the study has a few limitations. For one, it didn’t show that supplements caused the increased and reduced mortality risk but simply revealed an association between the two. It also didn't uncover which formula had the most vital link to mortality: calcium, vitamin D, or a combination of the two.

Thacker told Health that the amount of calcium and vitamin D participants took could have influenced the study’s results.

“This study used too much calcium if one was also ingesting it in the diet, and likely not optimal vitamin D intake for most adult women,” she said. “Calcium supplements do not need to be taken if one ingests enough from the diet and has adequate vitamin D levels.”

According to the National Institutes of Health, the recommended dietary allowance (RDA) of calcium for women aged 51 to 70 is 1,200 mg, and the RDA of vitamin D for women in this age group is 600 international units.

The study builds on previous research examining how the supplements affect heart health individually.

Some studies have linked vitamin D supplementation with reduced cancer risk, Lala-Trindade said.

While observational studies have linked low vitamin D levels with an increased chance of developing cardiovascular disease, she added, "supplementation has never been shown to decrease cardiovascular risk in randomized controlled trials, [which are] the gold standard of testing efficacy of a given intervention."

Calcium, on the other hand, has been associated with increased cardiovascular risk in both randomized trials and observational studies, according to Lala-Trindade.

Related: 15 Foods High in Calcium

What to Consider Before Taking New Supplements

The new research underscores the need to speak with a healthcare provider before adding new supplements to your routine. Even if you’ve started taking supplements without advice, experts say it’s still worth checking in with a medical professional.

Though calcium and vitamin D are sometimes recommended for postmenopausal women, your healthcare provider may decide they’re not necessary for you.

Lala-Trindade said that healthcare providers consider a patient’s risk of developing conditions and complications before making recommendations.

“I think the cardiovascular community has appreciated that vitamin D and calcium supplementation on a broad scale may, in fact, increase cardiovascular events, especially for those at a heightened risk,” she added.

Still, Lala-Trindade said the findings of this study may not be significant enough to shift current recommendations.

“While the study is important,” she explained, “I do not know if this study will be practice-changing.”

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