Breaking Myths and Misconceptions

Do Vitamin D Supplements Really Improve Your Health?

Originally published January 13, 2020

Last updated April 29, 2024

Reading Time: 3 minutes

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Can vitamin D supplements prevent cancer, protect your heart and step up physical performance? Read on to see what science has to say.

Vitamin D has a good reputation. It purportedly is a multitasker with the ability to boost your immune system, improve physical performance, maintain a healthy heart, support strong bones and lower your cancer risk. But is it true or is it hype?

The fact is we all need vitamin D — it helps our bodies absorb calcium, which helps us build strong bones. It also plays a role in keeping our muscles, nerves and immune system functioning properly. We can get vitamin D from the foods we eat, from exposure to the sun or from supplements. Here’s a look at what vitamin D supplementation can and can’t do for your health.

Claim: Vitamin D supplements boost your immune system.

Because of vitamin D’s role in regulating your immune system, it’s natural that scientists are exploring whether vitamin D supplementation can prevent viral infections. One small study of schoolchildren found that those who took vitamin D supplements were less likely to get the flu than those who didn’t take the supplements, while another study of adults found no difference in the rate of upper respiratory infections.

Verdict: The jury is still out.

Claim: Vitamin D supplements improve heart health.

This idea was an outgrowth of an interesting scientific observation: “Since the early part of the 21st century, there has been compelling epidemiological evidence that suggests that vitamin D deficiency is a risk factor for heart attack, stroke, congestive heart failure and other medical conditions that increase an individual’s risk factors for heart disease,” says Helga Van Herle, MD, a cardiologist at Keck Medicine of USC and associate professor of clinical medicine at the Keck School of Medicine of USC.

But just because vitamin D deficiency is associated with heart disease, it doesn’t necessarily mean that vitamin D supplementation will lower that risk.

“In fact, a recent large analysis of randomized controlled trials failed to show that vitamin D supplementation protects against cardiovascular events, stroke or heart attack,” Dr. Van Herle says.

While vitamin D supplements may not decrease your risk of heart disease, lifestyle habits, like physical activity, quitting smoking and a heart-healthy diet, can.

Verdict: False.

Claim: Vitamin D supplements support bone health.

According to the National Institutes of Health (NIH), vitamin D enhances the absorption of calcium in the gut (which explains why it’s often used to fortify milk). On top of that, it ensures that the body has what it needs for bone mineralization, which keeps them strong.

But, when it comes to vitamin D supplementation, it’s difficult to know whether it improves bone health, because most research to date looks at vitamin D plus calcium. Among those studies, there is evidence that vitamin D plus calcium can slightly increase bone mineral density throughout the skeleton, according to the NIH; however, a large study found that vitamin D alone doesn’t decrease the risk of bone fractures.

Verdict: The jury is still out.

Claim: Vitamin D supplements improve physical performance.

Unfortunately, a daily vitamin D supplement will not make you a better athlete. An analysis of randomized controlled trials found that vitamin D supplementation does not improve physical performance in athletes.

Verdict: False.

Claim: Vitamin D supplements lower your cancer risk.

So far, the evidence on vitamin D supplements and cancer is conflicting. Some studies have found an association between lower vitamin D levels and an increased risk of colorectal cancer, but association doesn’t mean causation. A large randomized controlled trial found that vitamin D and calcium supplementation did not lower the risk of colorectal cancer in women, and yet another study found no effect of vitamin D supplementation on cancer risk overall. Perhaps this is why the American Academy of Family Physicians and the U.S. Preventive Services Task Force do not recommend vitamin D supplementation for this purpose.

Verdict: The jury is still out.

So, what’s the bottom line when it comes to vitamin D supplements and your health? While research seems to have ruled out any benefit for heart health and physical performance, more studies are needed to make any definitive conclusions about its impact on your immune system, bone health and cancer risk.


Deanna Pai
Deanna Pai is a freelance writer and editor.

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