When it comes to the new coronavirus, the data is still too sparse to answer definitely how or whether one supplement or another might help the immune system fight off the virus. What microbiologists who study the immune system do know about our body’s defenses is that ramping up our immune system to be on “high alert” or globally boosting it to fight off every and any germ out there is actually a flawed concept, says Michael N. Starnbach, PhD, a professor of microbiology at Harvard Medical School in Boston. The immune system is designed to recognize things that are foreign in our body and clear those foreign things out, but those cells and responses are finely tuned, says Dr. Starnbach. “If the immune system were too active, it would attack our own tissues, which can happen in some autoimmune diseases, such as rheumatoid arthritis and Crohn’s disease,” he says. There’s really only evidence that supplements improve immune function in populations that are truly malnourished, which is rarely the case in the United States, according to Starnbach. “People can be more susceptible to diseases when they are severely malnourished, but it doesn’t mean that replenishing higher-than-necessary amounts of vitamins and nutrients in someone is going to make their immune system work that much better," he says. The researchers that led that study noted in the paper that those links between supplement use and COVID-19 risk should be considered preliminary. Even though the data included a large number of people, the data was self-reported, participants didn’t report the dose of supplements they were taking, and there were several potentially confounding factors the researchers weren’t able to control for; for instance, perhaps people who voluntarily downloaded and logged symptoms in the app were better at other health behaviors that could have ultimately been effective at lowering their COVID-19 risk, too. Additional, more tightly controlled clinical trial data (instead of this observational data) is needed before researchers would be able to conclude with certainty if any of these supplements might help protect people against COVID-19. 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. Other, older evidence suggests some vitamins and supplements may reduce the likelihood of getting sick from a respiratory virus or reduce the amount of time a person is sick with a virus, especially if a person is deficient in some way, according to Tod Cooperman, MD, the president and founder of ConsumerLab.com, a provider of independent test results and information designed to help consumers and healthcare professionals identify the best-quality health and nutrition products. Again, we don’t know whether the vitamins and supplements we have evidence for would yield the same effects against the novel coronavirus. “Right now, if you’re concerned about catching the coronavirus or any other virus, taking a basic multivitamin every day is a safe way to potentially ensure you’re not deficient in any area [of basic vitamins/minerals],” says Dr. Cooperman. “Eating well, getting good sleep, and exercising will also help keep you as healthy as possible and keep your immune system strong,” he says. RELATED: Coronavirus Shopping List: What to Buy and Skip Here’s more about what is known about specific vitamins and supplements that may affect viral infections. As always, let your doctor know about all supplements you are taking or plan to take, as they can pose unintended health risks for certain groups or interact with other medications you’re taking. RELATED: Coronavirus and Prescription Medications: Should You Stock Up? RELATED: What You Need to Know About Living With a Compromised Immune System During the COVID-19 Outbreak And remember, the novel coronavirus is an entirely new threat. There’s no strong data yet on how particular vitamins or supplements may or may not thwart it, says Dr. Lin. (Most of the studies referenced here investigate how supplements work against other types of viruses.) “We really don’t know if they would provide support in fighting off COVID-19 [the disease spread by the novel coronavirus],” she says. Here’s what we do know. Elderberry Some data suggests that elderberry (taken in teas, lozenges, gummies, or pills) can reduce flu virus production and help people recover from flu faster, Lin says. A study published in March 2019 in the Journal of Functional Foods found that compounds from elderberries can inhibit the virus’s entry and replication in human cells and help strengthen a person’s immune response to the virus. There is no really good data for the common cold and elderberry, Lin says. RELATED: Cold and Flu: Everything You Need to Know Zinc does have some data suggesting it can support your immune system, and it may help you fight off infection in common colds faster, Lin says. A meta-analysis published in the journal JRSM Open in May 2017 found evidence that zinc lozenges can shorten the common cold’s duration by over 30 percent. The findings recommended that the lozenges not contain citric acid or salt citrate. “[It’s an approach] that you can think about taking within the first few days of infection,” she adds. Remember, zinc has not been tested on the new coronavirus, but it has been tested with other viruses like the common cold, Cooperman says. When it comes to other viruses, zinc lozenges work by inhibiting virus activity in the throat, when the infection is just starting to spread, lessening those symptoms. So taking those lozenges soon after you begin experiencing symptoms may help, Cooperman explains. “It’s fairly safe for a week or two. You want to suck on the lozenges, but not chew, so your throat is continually coated with zinc,” he says. Make sure you follow the instructions on the package and that you’re not taking more than the recommended dose, Cooperman adds. It’s also worth noting that the National Institutes of Health currently recommends against using zinc supplements above the recommended allowance (for adults, 8 milligrams [mg] daily for women and 11 mg for men) to prevent COVID-19. RELATED: The Best Food Sources of Zinc Vitamin C is associated with some benefits for colds, Lin notes. (The common cold can be caused by a type of coronavirus.) A meta-analysis of 29 trials, including 11,306 people, looked at how taking at least 200 milligrams (mg) per day of vitamin C affected risk and management of colds. The study, published in Cochrane Database of Systematic Reviews, found that vitamin C didn’t reduce the incidence of colds in adults, but it did shorten the duration of colds by 8 percent. A subgroup of studies in the Cochrane analysis looked at marathon runners, skiers, and army troops doing heavy exercise in very cold conditions and found that supplements of at least 200 mg of vitamin C every day appeared to cut the risk of contracting a cold by 50 percent. Lin recommends aiming to get the vitamin C you do need daily and focus on getting it from food sources, rather than supplements. “I would encourage eating vitamin C–rich vegetables to boost your levels of vitamin C,” she says. The recommended daily amount of vitamin C for adults is 75 to 90 mg a day, according to the National Institutes of Health. One orange contains about 75 mg, a green pepper contains about 60 mg, and a half cup of Brussels sprouts has almost 50 mg. Taking very large doses of vitamin C isn’t recommended; once doses go above 400 mg, vitamin C is just excreted in the urine, according to the Harvard Health Letter. RELATED: Immune-Boosting Smoothie Recipes Vitamin D is important for maintaining a strong immune system, according to Cooperman. And low levels of vitamin D are associated with frequent colds and influenza, according to the National Institutes of Health. Because we get a lot of the vitamin D we need from sunshine, many people see their levels drop off during the winter months, says Cooperman. He recommends 600 to 800 IU or 15 to 20 micrograms if you decide to take supplements. But remember, it’s always a good idea to check with your doctor before starting a supplement to make sure it’s okay for you, and check that it won’t interfere with other medications you may be taking or your other health needs. A meta-analysis of prospective trials published in the journal BMJ in 2017 found that vitamin D reduced the odds of respiratory infection by 42 percent in people who were vitamin D deficient at the start of the study. Note: Dosage matters. Taking a daily D3 dose of between 300 IU and 4,000 IU was more effective than taking a large monthly dose, according to the BMJ report. In a randomized, double-blind placebo trial of 5,110 older adults who were vitamin D deficient (published in August 2019 in the journal Clinical Infectious Diseases), the data again showed that large doses may not be beneficial in preventing respiratory infection. Participants were given 200,000 IU at the start of the study followed by 100,000 IU monthly, with a mean follow-up of 1.6 years. Investigators found no reduction in the number of acute respiratory infections compared with placebo. Given the link between vitamin D and respiratory infections, researchers are currently studying whether there’s a link to COVID-19 outcomes. A group at Northwestern University in Chicago has collected population-level data that suggests people from countries with higher known levels of vitamin D deficiency had higher levels of mortality linked to the novel virus, according to a May 2020 press release. A group of researchers in Ireland conducted a similar analysis and reached the same conclusion, according to another press release in May. It’s worth noting that neither group’s data has yet been published in a peer-reviewed medical journal. And the findings only identify a potential relationship between vitamin D levels and COVID-19 outcomes in groups of people (neither group looked at an individual’s vitamin D levels and connected it to his or her COVID-19 outcome). Additional research in randomized controlled trials that track individuals’ vitamin D levels and how they specifically fare with COVID-19 will need to be done to more conclusively prove the role vitamin D, and specifically vitamin D supplement intake, plays in response to the virus. What the collective evidence points to is that being deficient in vitamin D may hamper immune function and your body’s ability to protect itself against COVID-19. If you’re not deficient, vitamin D supplementation won’t really provide a lot of additional benefit, but if you are deficient, taking the supplement (or increasing dietary intake and healthy sun exposure) can strengthen immunity, says Cooperman. Apple cider vinegar Though apple cider vinegar (ACV) does boast some other health benefits, there isn’t evidence to show that ACV affects immune function or that taking it regularly improves your chances of fighting off viruses, Lin says. Turmeric While there is some evidence turmeric may yield some health benefits, including help with high cholesterol management, glucose control, and digestive issues, there isn’t specific evidence that it can help fight off a virus, says Lin. There is, however, evidence suggesting one of the active compounds in turmeric (curcumin) does act on immune function in some way, though how those effects may or may not benefit health is still unclear, according to a review published in the Journal of Clinical Immunology.
