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Dietary Supplements May Reduce COVID-19 Risk in Women

person holding handful of supplements

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Key Takeaways:

  • Researchers conducted an observational study to see whether people taking certain dietary supplements were less likely to test positive for COVID-19.
  • Women taking multivitamins, omega-3 fatty acids, probiotics or vitamin D were less likely to contract COVID-19, but the same result was not seen in men.
  • More research is needed—including randomized controlled trials—before specific recommendations can be made about supplements and COVID-19.

In new research published in the journal BMJ Nutrition, Prevention & Health, researchers investigated whether people taking different dietary supplements, including vitamin D and omega-3 fats, were less likely to test positive for SARS-CoV-2, the virus that causes COVID-19.

Past studies have shown that a healthy, balanced diet can support immunity. And when a diet is incomplete, dietary supplements can fill in some gaps.

Vitamins, minerals, and other dietary supplements have been shown to play key roles in supporting immune function. Past studies have shown that supplements such as vitamin D, zinc, elderberry, and probiotics may help reduce colds and/or flu.

Given the history of studying dietary supplements and their effect on viruses, researchers have been curious if any dietary supplements can reduce the risk of COVID-19 infection.

And researchers aren’t the only ones who are curious about supplements. Sales of dietary supplements in the United States were more than 50% higher in March 2020 than they had been a year earlier. In the single-week period ending March 8, 2020, sales of elderberry supplements increased by 255% and sales of zinc supplements increased by 415%.

Using an app-based community survey with 372,720 subscribers in the UK, the researchers collected self-reported information on the regular use of dietary supplements. Users had to be taking supplements at least three times a week for at least three months during the pandemic.

The app recorded supplement use with a simple ‘yes’ or ‘no’ answer, but did not collect details on the dosage of the supplement. 

The app was used to track the outcomes of people taking these supplements:

  • Probiotics
  • Omega-3 fats
  • Multivitamins
  • Vitamin D
  • Vitamin C
  • Zinc
  • Garlic

The researchers looked at how these supplements affect COVID-19 risk stratified by age, gender, and body mass index (BMI).

What Did the Study Find?

Of the 372,720 app users, 23,521 tested positive for COVID-19. Multivariate logistic regression adjusting for age, sex, BMI and health status at sign-up was applied so researchers could ably investigate the association between supplement use and COVID-19 in this UK cohort.

Among the app users, about half were taking supplements. The researchers found that after adjusting for age, sex, BMI, and health status:

  • Those taking probiotics were 14% less likely to test positive for COVID-19 infection.
  • Those taking omega-3 fats were 12% less likely to test positive.
  • Those taking multivitamins were 13% less likely to test positive.
  • Those taking vitamin D were 9% less likely to test positive.

Cristina Menni, PhD

Our research is an observational study and not a clinical trial, so it is quite speculative, and we can’t make strong recommendations based on the data we have.

— Cristina Menni, PhD

The researchers described these effects as modest but significant. And they observed no differences with COVID-19 in those taking zinc, vitamin C or garlic.

So does this mean you need to run out and buy some supplements? Not quite yet.

“Our research is an observational study and not a clinical trial, so it is quite speculative, and we can’t make strong recommendations based on the data we have,” explains Cristina Menni, PhD, a lecturer at King's College London, and one of the researchers on this study. “Our results support the need of randomized controlled trials of the identified supplements.”

“I think this study is interesting as it is one of the first large studies observing a relationship between certain supplements and COVID-19 risk,” says Lisa Young, PhD, RDN, CDN, a dietitian nutritionist in private practice, an adjunct professor of nutrition at NYU. “It can be helpful for future studies.” 

Young still recommends a food first approach. “Following a nutritious diet is STILL the first line of defense for maintaining good health,” says Young. “I advise clients to get their intake of nutrients from food.” 

Differences in Females and Males

Interestingly, the protective effects from probiotics, omega-3 fats, multivitamins, and vitamin D were observed in those that self-identified as female, but the same effects were not observed in those that self-identified as male.

The researchers found that females taking probiotics, omega-3 fatty acids, multivitamins, and vitamin D were less likely to be infected across all age groups and BMI categories, but no protective association was observed in males overall.

In a smaller sub-group analysis, men under age 40 taking multivitamins and men aged 40–60 years taking omega-3 fats were less likely to be infected with COVID-19.

So why did the supplements appear to be more effective in women?

Verywell asked Menni, who explained, “this difference may be due to the differences in immune systems between males and females. Alternatively, it could be due to reporting bias, with one sex reporting their supplementation more accurately.”

The study lists other possible reasons, including:

  • Females may have a more resilient immune system and more circulating B cells.
  • Differences in body weight/composition between males and females, which could affect supplement dosing.
  • Residual confounding due to differences in health-related behaviors for females and males (females may be more precautionary and health-conscious).

What Makes These Supplements Effective?

In the research study, the investigators list reasons why the dietary supplements may help reduce the risk of COVID-19.

Vitamin D and COVID-19 have been well-studied, and Menni says there is more to come.

“There are ongoing randomized controlled trials looking at the effects of vitamin D on COVID-19 protection and severity,” says Menni.

The research paper explains that “vitamin D influences the function of antigen-presenting cells, T cells and B cells,” which are important for immunity.

Likewise, multivitamins may be beneficial because they offer an array of nutrients which have antioxidant properties and roles in supporting the immune system.

A multivitamin is like an insurance policy in case you have any nutrients needs that are not being met through diet alone. The research paper says “specific micronutrient deficiencies, including zinc, selenium, vitamin A, vitamin D and vitamin E, have been shown to be detrimental during viral infections.”

Lisa Young, RD

Following a nutritious diet is STILL the first line of defense for maintaining good health. I advise clients to get their intake of nutrients from food.

— Lisa Young, RD

Omega-3 fats are known to be anti-inflammatory, but the researchers say “whether this is a mechanism by which they reduce risk of testing positive for SARS-CoV-2 is not clear.” More research is needed to illustrate the connecting between omega-3 fats and COVID-19 risk.

Probiotics play a role in the immune system and can alter gut microbiota. Studies show that they may play a role in generating antiviral metabolites.

Interpret with caution

While you can certainly take any of these supplements (in safe doses as advised by your health care provider), this study is not enough to conclusively say that the supplements helped prevent COVID-19.

The study used self-reported data, which can introduce errors, and it didn’t account for how much of each supplement was taken by app users. Plus, the app users may have been taking supplements in addition to the seven that the researchers asked about, and those were not accounted for.

Finally, the app didn’t capture robust information on other ways to reduce the risk of COVID-19, including hand washing, social distancing and using masks. These may be the reasons why certain people didn’t get COVID-19, rather than supplement use. More research is definitely needed. 

What This Means For You:

What this means for you: You can certainly take vitamin D, multivitamins, omega-3 fats and probiotics in safe doses, but it’s too soon to say whether they can truly lower your risk for developing COVID-19. Large clinical trials of supplements are needed before any evidence-based recommendations can be made. 

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