The Truth About Supplements for the New Coronavirus (COVID-19)

Covid-19 and supplements

The new coronavirus disease has a lot of people worried, and this has created an ideal breeding ground for misinformation. You’re probably aware of the chain emails, online health articles, and even news stories that have been touting new ways to prevent or treat the disease. Supplements companies are getting in on it, too, with claims that supplements like vitamin C, vitamin D, and zinc can help.

At Labdoor, where we test and sell supplements, our highest priority is to keep consumers safe and well-informed, especially when there are risks of false claims and overdosing, as we’re seeing during this coronavirus outbreak. Research shows that vitamin C, vitamin D, and zinc are critical for our immune systems to function, but beyond that, the evidence gets a little hazy.

Top takeaways:

  • Adequate levels of nutrients, including vitamin C, vitamin D, and zinc, are important for a healthy, functioning immune system.
  • There is no evidence to date that any supplements prevent, cure, or treat the new coronavirus disease (COVID-19).
  • Zinc lozenges may work by preventing certain coronaviruses from replicating, but this has not been studied with the new coronavirus.
  • The types of viruses that can cause the cold and flu are very different from the virus that causes COVID-19; they cannot be treated the same way.

Vitamin C

Vitamin C is probably the most widely marketed vitamin to boost the immune system, especially to fight off upper respiratory tract infections like the cold and flu. And with the new coronavirus, some people are saying that vitamin C cures colds, which can be caused by coronaviruses, so it must at least help a little for COVID-19. There are a few reasons why this is false.

First, colds and COVID-19 are caused by very different viruses. Coronaviruses are, in fact, a large family of hundreds of viruses. Most usually cause the common cold. But of course, we know of the current coronavirus disease, SARS (severe acute respiratory syndrome), and MERS (Middle East respiratory syndrome), which are all caused by coronaviruses, too. What applies to cold viruses can’t necessarily be applied to the new coronavirus.

Second, vitamin C does not cure colds, and any benefits it has for preventing colds are limited. Vitamin C became famous in the 1970s when researcher Linus Pauling published research that said it prevented and cured the cold. Since then, however, researchers have not been able to confirm his claims. Perhaps some of the misinformation with vitamin C and COVID-19 comes from the fact that researchers in China are testing it in COVID-19 patients who get pneumonia. They just started the study in February, and we won’t have any results until later this year. Keep in mind that the study uses intravenous vitamin C at very high doses, and this is not the same as typical vitamin C supplements that you take orally.

Some researchers suggest that people who may benefit from vitamin C supplements are those who may not be getting enough. It’s true that our immune systems depend on vitamin C (among other nutrients) to ward off germs. Vitamin is directly involved in the activity of your immune cells, and we need it to absorb plant-based iron from our diets. (Iron is also important for a healthy immune system.) But there’s little evidence that taking more vitamin C than is recommended helps the immune system much, and no evidence to date that it can prevent, cure, or treat the new coronavirus disease.

Vitamin D

We all know that vitamin D plays a role in keeping our bones intact and strong, but it’s also important for our immune systems. With respiratory infections, inadequate vitamin D levels have been linked to an increased risk of getting the cold and flu.

Unlike with vitamin C, where the vast majority of people get enough, regardless of age, vitamin D deficiency is common, especially in older people. National surveys estimate that about 25% of all adults don’t get enough vitamin D, and many of those people are 60 years old or older. Unfortunately, the research on whether vitamin D supplementation can help with respiratory infections is inconclusive. There is no evidence that vitamin D supplementation will prevent or treat COVID-19.


You may have seen the email from a doctor that went viral, promoting zinc lozenges as a way to fight off the new coronavirus. But don’t be fooled. Zinc is not the magic cure that this email makes it out to be.

It’s important to recognize that zinc supplements come in different forms, including lozenges and pills. The lozenges work in the throat and are thought to fight off colds by preventing the viruses from multiplying. In a a review of three studies on zinc acetate lozenges, researchers found that the lozenges sped up recovery from colds by up to three times. In two of the studies, patients started taking lozenges within 24 hours of getting cold symptoms, and each lozenge contained at least 75mg of elemental zinc.

Whether zinc lozenges work against the new coronavirus is still a mystery. Also, if you look at safety limits for zinc on the National Institute of Health’s website, you’ll see that adults should not get more than 40mg per day. The studies above used much higher zinc amounts than this, and as we’ll discuss below, too much zinc can be dangerous.

Now, zinc pills work by addressing low zinc levels, and we know that zinc is important for the immune system. Most of us in the U.S. probably get enough zinc, but national surveys suggest that almost half of adults 60 years or older may be lacking. For these people, we don’t know if zinc supplementation really gets the immune system back to normal. However, some researchers suggest that foods rich in zinc like meats, legumes, and nuts may be useful in preventing zinc deficiencies in older people.

There are no research studies to date on zinc supplements and the virus that causes COVID-19.

Other things to be aware of

In addition to the research above, it’s important to realize that supplements, like medications, can affect the body in profound ways, and they come with risks.

  1. Taking too much of any supplement comes with risks. Too much vitamin C or zinc for example, can cause diarrhea, nausea, and abdominal cramps. High intakes of zinc can even reduce your immune function. Too much vitamin D and you risk extreme weight loss, heart arrhythmias, and calcium buildup, which can damage your heart, blood vessels, and kidneys. Consult your doctor before taking supplements, and follow their recommendations for how much is safe.
  2. Supplements can interact dangerously with other supplements and medications. Certain antibiotics and diuretics, for example, can interfere with zinc. The NIH notes that vitamin D can interact with steroids and certain weight loss medications, and vitamin C may interact with cholesterol-lowering medications. If you are considering taking vitamins, talk to your doctor about whether your supplements and medications will be safe together.
  3. Supplements are being falsely marketed. This past week, the FDA cited seven companies for falsely marketing their products to cure, treat, and prevent the new coronavirus disease. Remember, no supplements have been tested for the treatment of COVID-19. In fact, while researchers are investigating new vaccines and medications to prevent and treat the disease, no pharmaceutical products have been approved for the disease either.
  4. Supplements labels can often be inaccurate. Even if your doctor recommends that you take supplements, make sure to verify product claims. Labdoor’s research shows that vitamin C supplements, for example, can have less than half of the vitamin C they claim. Vitamin D supplements, on the other hand, may have more than 40% more vitamin D than they claim. Sometimes, products just have too much. Almost half of the zinc supplements that Labdoor tested, for example, had more than 40mg of zinc per serving, exceeding the tolerable upper limit of how much zinc you should eat in a day.

In conclusion

How the new coronavirus disease is progressing can be unsettling, but that doesn’t mean you don’t have options. While there is no evidence yet to suggest that “immune-boosting” supplements work to fight the virus, it’s always a good idea to consider whether you are doing what you can to set your body up for success, including getting enough sleep, checking with your doctor or nutritionist if you are getting the nutrients you need, and practicing basic hygiene habits like washing your hands frequently and avoiding crowds. The CDC and WHO have both also published guidance on how best to protect yourself against the disease.