Skip to main content

Fact check: Facebook post about vitamin D and respiratory illness is missing context

Valerie Pavilonis   | Paste BN

The claim: Taking vitamin D decreases your chances of getting a respiratory infection by 42%.

As the United States logs hundreds of thousands of new cases of COVID-19 a day and research shows that vaccines only partially prevent infection from the omicron variant, misinformation about COVID-19 treatments is spreading.

A Jan. 26 Facebook post claims taking vitamin D can reduce your chances of getting a respiratory infection by 42%. The post garnered almost 1,000 shares in a day. 

Follow us on Facebook! Like our page to get updates throughout the day on our latest debunks

Vitamin D is both a hormone produced by humans and a nutrient found in some foods, according to the Harvard T.H. Chan School of Public Health. Known for helping the body absorb phosphorus and calcium – both needed for healthy bones – vitamin D can also help reduce inflammation and control infection. 

Still, the claim that taking vitamin D reduces risk of respiratory infection by 42% is misleading. While that figure can be traced back to a specific study, nuances in that study mean the 42% number can't be applied to the general population. Vitamin D supplements can significantly lower the risk of respiratory infections in those with vitamin D deficiencies, but the benefit to those with sufficient vitamin D levels is much more modest, experts say.

42% figure tied to one group, not general population

The Facebook post was, according to the poster, based upon a 2017 study published in the BMJ that looked at how vitamin D supplements affected the frequency of acute respiratory tract infections.  

“Our study reports a major new indication for vitamin D supplementation: the prevention of acute respiratory tract infection,” the authors wrote. “We also show that people who are very deficient in vitamin D and those receiving daily or weekly supplementation without additional bolus doses experienced particular benefit.”

Fact check: Claim that cilantro removes heavy metals from the brain is unproven

According to the study, vitamin D supplements had a “strong protective effect” for those with vitamin D levels of less than 25 nanomoles per liter, which is the upper bound for vitamin D deficiency according to the U.K. Department of Health.

In short, the numbers in the study line up with the 42% figure in the Facebook post, but that finding applied only to those with vitamin D deficiency, not the general population.

Since 2017, other researchers have looked more closely at the relationship between vitamin D and respiratory infections. In one 2021 study – authored by Adrian Martineau, a professor of respiratory infection and immunity at Queen Mary University who also led the 2017 study – scientists found a smaller reduction of 8% associated with taking a vitamin D supplement.  

Taking vitamin D can help your health

A significant portion of people across the world are vitamin D deficient, according to Dr. Michael Holick, a professor of medicine at Boston University. 

During most of a day, he said, lack of sunlight prevents people from producing it on their own. According to a 2010 article from the International Journal of Health Sciences, over 1 billion people worldwide are vitamin D deficient.

Some experts advocate for patients to take vitamin D. Holick said he recommends at least 2,000 units of vitamin D a day, but vitamin D occurs naturally in only a few foods – wild salmon, for example, or mushrooms that have been exposed to sunlight. Camargo also recommends a daily supplement for those with low vitamin D levels, a number that can be determined with a blood test. 

“A reasonable target – for improved general health – is the 32-40 ng/ml range,” Camargo wrote in an email. “Some people aim for higher – 40-50 ng/ml – and I think that’s fine but, for general health, I would not push it higher.”

Fact check: Root canals do not impair immune system, experts say

Holick noted recent research has identified other benefits of sufficient vitamin D levels as well. In one study published in the BMJ on Jan. 26, authors concluded over five years, 2,000 units of vitamin D supplementation a day reduced the incidence of autoimmune disease by 22%.

A 2020 study also found COVID-19 positivity rates were higher among those with vitamin D deficiencies than those with sufficient levels.

Our rating: Missing context

Based on our research, we rate MISSING CONTEXT the claim that taking vitamin D reduces your chances of getting a respiratory infection by 42%. According to the study the claim was based on, taking a certain amount of vitamin D did result in a 42% reduction, but only in people who were vitamin D-deficient in the first place. Other studies have found lesser impacts.

Our fact-check sources: 

Thank you for supporting our journalism. You can subscribe to our print edition, ad-free app or electronic newspaper replica here.

Our fact-check work is supported in part by a grant from Facebook.

Facebook Twitter Email