The recent data found a lower rate of infection with COVID-19 among women who used multivitamins, probiotics, omega-3 fatty acids, and vitamin D supplements. On the other hand, use of vitamin C, zinc, and garlic supplements showed no effect in lessening COVID-19 risk. None of the supplements were linked to a protective effect against COVID-19 in men. The data set included thousands of people who answered questions about supplement use and COVID-19 infection on the COVID Symptom Study app, which was available in the United Kingdom, United States, and Sweden. While the findings are intriguing and constitute some of the first data on supplement use and risk of COVID-19, the researchers at King’s College London in the United Kingdom are quick to warn that their work is preliminary, given that it’s based on self-reported data, and certain factors may not have been adequately controlled for. RELATED: Can a Supplement Protect Me Against the New Coronavirus? “The bottom line is our research is an observational study and not a clinical trial,” says the study’s senior author, Cristina Menni, PhD, a research fellow at Kings College London. “We can’t make strong recommendations based on the data we have.” The research, which was published April 19 in the journal BMJ Nutrition, Prevention and Health, is exciting because it’s some of the first large-scale data available on supplement use and COVID-19 risk and provides a good jumping-off point for further research, Dr. Menni says. “This is probably the biggest study to date looking at COVID-19 and supplement use in a real-life setting.”
Probiotics, Omega-3s, Multivitamins, and Vitamin D Linked to Lower COVID-19 Risk
Menni said that since the beginning of the pandemic, there’s been plenty of speculation about the benefits of taking vitamins to bolster the immune system against COVID-19, but very little data to support any claims. The UK supplement market skyrocketed by 19.5 percent at the start of the first lockdown in March 2020, for example, with a 110 percent rise in vitamin C sales and a 93 percent increase in multivitamin sales. In the United States, zinc sales increased by 415 percent over a seven-day period in March 2020, according to the new study. Menni and her team analyzed data from a subset of 445,000 COVID Symptom Study app users. The app, which launched in late March 2020, also collected user information about symptoms of COVID-19, COVID-19 test results, stress and mental health, changes in weight, diet and exercise habits, and vitamin and supplement use. The app also asked users for information such as age, location, body mass index, ethnic background, socioeconomic status, and whether they’re a healthcare worker or not. When it came to vitamin intake, the researchers asked users if they had taken any of the following supplements at least three times a week for more than three months: omega-3s, probiotics, garlic, multivitamins, vitamin D, vitamin C, and zinc. The data set included self-reports from 45,757 Americans who used the app between May to June 2020. Seventy-one percent of American users reported taking supplements while 29 percent didn’t. Over the three-month period, 3,213 people reported having tested positive for COVID-19. Americans who reported taking probiotics, omega-3 fatty acids, multivitamins, and vitamin D respectively had an 18 percent, 21 percent, 12 percent, and 24 percent reduced risk of reporting testing positive for COVID-19 during the three-month period. When the researchers controlled for sex, age, BMI, smoking habits, and underlying health conditions, the data revealed that for the men in the study, there was no protective effect against COVID-19 linked to use of any of the vitamins and supplements. The UK and Swedish data showed similar patterns. Menni says it’s unclear why the data showed a link between supplement use and COVID-19 for women but not for men. It’s worth pointing out that according to the app data, women also tended to report staying at home and canceling plans more than men; and there were more women in the study (including from the United States, the United Kingdom, and Sweden).
Researchers Say More Data Is Needed Before People Change Their Supplement Behaviors
The researchers point out several significant limitations of the data in the paper. For starters, the study relied on users’ self-reporting their vitamin intake with a list of seven options. The researchers don’t know how much users were taking of each nutrient and whether they were taking any other supplements. A “health bias” may also be at work, according to Menni. Users voluntarily downloaded the app and tracked their COVID-19 symptoms routinely; the majority of users were taking supplements, meaning the group may have been more health conscious to begin with — and thereby more careful with other health behaviors, like hand-washing, wearing a mask, and social distancing, which we know help protect against COVID-19. David Smith, MD, the head of the infectious diseases division at the University of California in San Diego, who was not involved in the new study, suggests that people wait before stocking up on vitamins and supplements in an attempt to stave off COVID-19. “I could imagine people who took probiotics for COVID-19 prevention would also be better at wearing a mask,” he says. If that is the case, the link between probiotics and lower COVID-19 risk may be a correlation of behavior or other factors: probiotics users were stricter about wearing masks and other health measures, and mask-wearing may have actually been the reason they were less likely to get COVID-19. “I would not recommend my patients take [supplements]. I would want randomized controlled trials to really know if they work. There is very little data to show that vitamins and supplements improve health, as most people get these regularly in their diet,” Smith says.
What Does Help Boost the Immune System’s Ability to Fight COVID-19? Sleep, Managing Stress, Eating Well, and Moving
There are four pillars to strengthening your immune system, according to Yufang Lin, MD, an integrative medicine doctor at Cleveland Clinic in Ohio. They include nutrition, adequate sleep, managing stress, and regular exercise. If you’re skimping on sleep or not managing stress, supplements probably aren’t going to make up the difference, Dr. Lin says. Overall, she said the new study adds to the growing library of research on supplements’ effectiveness in strengthening the immune system. RELATED: How to Keep Your Immune System Healthy “There are a lot of nutrients that are important in supporting your immune response, so if you do get exposed you don’t get sick as much. Whether you get these vitamins through supplements or food is up to the individual, but I would certainly start with food,” she said. Consumers should rely on vitamins only if they’ve been tested and know they’re vitamin deficient, if their diet is lacking in fresh produce, or if they have a medical condition that requires supplementation, Lin said. Meanwhile researchers continue to investigate potential links between supplement use and risk of COVID-19 infections. Earlier this year, researchers at the Chinese University of Hong Kong found that the microbiome, or the variety of bacteria in the gut, may influence patients’ immune system response to COVID-19 and, in turn, the severity of disease. The study, published in April 2021 in the journal Gut, is just one in a series of large-scale research efforts to better understand if supplements — in that case, probiotics — can help in reducing COVID-19 infection or duration of illness. Menni said there are also two clinical trials underway (one led by UK scientists and another run by a French team), looking at vitamin D and its potentially protective effect. RELATED: 11 Vitamin D Myths and Facts
