En español | There is a long-established link between nutrition and immune health. But when it comes to the coronavirus (SARS-CoV-2), scientists still don't have a definitive answer on whether certain vitamins and minerals can help stave off an infection or make one less severe.
"And that's because it's such a new phenomenon,” one that researchers are learning more about every day, says Walter Willett, M.D., professor of epidemiology and nutrition at the Harvard T.H. Chan School of Public Health. Nothing is known to prevent or cure COVID-19, the illness caused by the new coronavirus. However, “it's not impossible” that essential vitamins and minerals could provide some benefits, he adds.
The reason: Previous research has shown that lower-than-recommended levels of certain vitamins and minerals can impair immunity to respiratory viruses and other pathogens. Nutrient deficiencies have also been linked to higher levels of inflammation and longer periods of recovery from illness.
A few recent studies suggest an even more direct connection between certain vitamins and minerals and SARS-CoV-2. One observational report published in the Journal of Endocrinological Investigation found an association between vitamin D deficiencies and higher mortality risks from COVID-19 among patients in Italy. Another, published Sept. 3 in JAMA Open Network, found vitamin D deficiency was associated with increased COVID-19 risk. Others, yet to be peer reviewed, have drawn similar conclusions.
"The bottom line here is that I don't think anybody should be walking around with low levels or low intakes of important and essential micronutrients and minerals and vitamins at any time, but especially if they're potentially going to be infected with coronavirus,” Willett says. “It's just basically practicing good preventive nutrition to begin with.”
The nutrient gaining the most traction among scientists studying SARS-CoV-2 is vitamin D. The vitamin is found in some foods; it's also a hormone our bodies make when ultraviolet rays from sunlight strike the skin. Many know about vitamin D for its part in bone health. Equally important is its critical role in immune function, which is why it's in the spotlight with the coronavirus.
Data from countries where vitamin D deficiency is common show higher cases of COVID-19 infection and more serious health consequences from the illness, including death, says June McKoy, M.D., associate professor of medicine at Northwestern University Feinberg School of Medicine. This correlation has prompted scientists to further explore whether vitamin D has any protective qualities against SARS-CoV-2, even while other published reports dispute the link.
Another association of interest: One population most at risk for vitamin D deficiency — people who have darker skin color — is the same group that is being hit disproportionately hard by COVID-19 in the U.S. Hospitalization rates and deaths among Black Americans for COVID-19 are significantly higher than for their white peers. The same trend is reflected in the data for children with COVID-19.
"What we've seen is that the virus might actually be making use of that deficit,” McKoy says.
What's more, obesity, cardiovascular disease and type 2 diabetes — all risk factors for severe illness from COVID-19 — have been tied to low vitamin D levels.
So far, the research looking at vitamin D and SARS-CoV-2 is limited, but Willett says a number of studies are underway, so expect to see more data in the near future. In the meantime, if you are able to get outside for a few minutes a day, do it. The National Institutes of Health (NIH) says most people meet at least some of their vitamin D needs through exposure to sunlight. The recommended daily amount of vitamin D is at least 600 international units (IUs) a day for people ages 19 to 70, and at least 800 IUs for those older than 70; the tolerable upper intake for adults is 4,000 IUs per day, according to the NIH.
Stay-at-home orders and lockdowns brought on by the coronavirus outbreak have made access to frequent sunlight harder for some people in recent months, leading many to “almost certainly have lower vitamin D levels than they would have normally this time of year,” Willett says. For this population, Willett recommends a supplement to keep levels in the recommended range. Just remember to talk to your doctor before taking any supplement, since there's a potential it could interact with other medications.
Zinc is another nutrient that plays an important role in immune function, especially with regard to the production of white blood cells, which help to fight off infections. “The worse your infection, the higher your white blood cell numbers go up. And so if your zinc levels are low or insufficient, you won't have sufficient white cells to fight your infection,” McKoy says.
The mineral's role in inflammation suppression also has the attention of researchers studying SARS-CoV-2. Inflammation has been a common complication among patients with more severe COVID-19 cases, especially when the body's immune system overresponds to the infection and attacks itself — a potentially harmful condition known as a cytokine storm. But prior research has found that zinc can prevent the virus that causes the common cold from replicating; it can also decrease inflammation in the upper respiratory tract.
The question under the microscope now, McKoy says, is whether it can do the same in the lungs and lower respiratory tract, where the coronavirus and the inflammation it inflicts can cause serious damage. “Zinc might be the police officer that puts the handcuffs on the virus, and that's why we're excited about things,” she says.
Zinc is found in a variety of foods, including oysters, beef, lobster and crab. The NIH recommends 11 milligrams of zinc per day for men and 8 mg for women.
Coronavirus highlights need to focus on nutrition
All of this is not to say you should start megadosing on supplements as a preventive measure. Too much of certain vitamins and minerals can cause serious damage to the heart, kidneys and other organs. Instead, it's important to get the right amount.
Talking with your doctor is a great place to start, especially if you're worried you have a deficiency, McKoy says. A simple blood test can tell you if you are low in certain nutrients, and your doctor can prescribe a plan to bring your levels up.
For those who don't have a deficiency, a standard, inexpensive multivitamin-multimineral can act as “a nutritional safety net,” Willett says. “A lot of people who make a good attempt to have a healthy diet can have some gaps,” he adds. Plus, with millions of people out of work, the pandemic has put more Americans at risk for food insecurity, making healthy foods even further out of reach for some. “This almost for sure has magnified the problem,” he says.
The pandemic isn't just a good time to make sure your vitamin and mineral levels are healthy, Willett says. It's also an important time to examine your overall nutritional and metabolic health. Chronic health conditions associated with poor diet and lack of physical activity increase a person's risk for more severe outcomes from a coronavirus infection.
"And we know that America was not in very good shape, nutritionally, going into the epidemic, and that is one additional factor that's contributing to excess mortality,” says Willett, who speculates the country would have tens of thousands of fewer deaths if Americans were healthier. “Going back to normal when this is under control is not where we want to be. We want to go back to being better than before the epidemic,” he adds.
McKoy, who also advocates for vitamin C as an immune-system booster, says be sure to fill your diet with foods that are “colorful” and nutrient-dense — from broccoli and citrus fruits to fatty fish and legumes. And don't forget about the other measures that can help prevent COVID-19 — most importantly, limiting your exposure to the virus.
"Wear your mask, social distance, because you can take all of these vitamins and supplements we have mentioned and still get the coronavirus. It's not dependent on that,” McKoy says.