Vitamin C Rich Foods

Are There Supplements That Could Prevent COVID-19?

The arrival of COV-19 was unexpected, although the potential for a pandemic has always existed. Who can forget the 1918 Spanish influenza pandemic that killed between 50 and 100 million people? No wonder we’re social distancing now, washing hands, and doing what we can to help our immune system fight viruses, including the COVID-19 virus, a new virus that our immune system has never confronted.

We like to feel like we have some control over our fate, so it’s not surprising that people are looking for supplements that could offer protection against COVID-19 infection. Word is that companies that sell immune supplements are having trouble meeting the demand. But just because immune supplements are selling doesn’t mean they’re effective for the prevention of COVID-19 infection. You should always take supplement claims with a grain of salt!

Remember, we know little about this virus. So, don’t assume that “it can’t hurt” to take such-and-such a supplement. Plus, supplements can interact with other supplements and medications. Beware of advertisements online that say what their selling “boosts your immune system” or “protects against viruses.” Research the ingredients.  


Zinc as a treatment for COVID-19

Could zinc offer some protection against COVID-19 infection? Zinc is a mineral and micronutrient your body needs for a variety of functions, including reproduction, growth, and wound healing. Low levels of zinc are also linked with decreased insulin sensitivity and depression. Plus, zinc plays a key role in immune health.

What makes zinc of interest for COVID-19 infections? In vitro cell studies show that zinc reigns in the activity of an enzyme, RNA polymerase, that some viruses, including the SARS-COV virus, harnesses to replicate itself. If you block this key enzyme, that viruses use to replicate, the COVID-19 virus can’t make its proteins and is paralyzed. If you can get zinc into cells infected by the virus, it might cripple the ability of the virus to propagate itself. 

The problem with zinc is enough has to get into virally-infected cells enough to block RNA polymerase. Zinc doesn’t enter cells at a high enough level to be effective. However, scientists are experimenting with a combination of zinc and chloroquine, a drug used for malaria to treat cases of COVID-19. Chloroquine acts as an ionophore, a substance that opens the proper channels and helps zinc get into cells. So, zinc alone may not be enough to stop the novel coronavirus, but chloroquine could give zinc a boost so it can get into cells and potentially disable the RNA polymerase that COVID-19 hijacks for replication and survival.

As mentioned, researchers are already looking at zinc in combination with chloroquine as a potential weapon against COVID-19. So far, studies show that chloroquine boosts the entry of zinc into cells, but it’s too early to say whether the combination is effective against COVID-19 infection. Some studies are also finding early success with chloroquine or hydroxychloroquine, a different chemical form of chloroquine, even without giving zinc.

The benefit of hydroxychloroquine over chloroquine is it has fewer side effects, is more widely available, and is less expensive. The thought is that hydroxychloroquine will have the same ability to reign in the virus as chloroquine. These medications reduce the activity of COVID-19 by reducing viral replication and by making it harder for the virus to get into cells. So, the chloroquines have anti-viral activity independent of its interaction with zinc. 

There is some evidence that zinc is of benefit for other viruses.  For example, some studies show that taking 75 milligrams of elemental zinc within the first day of cold symptoms can shorten the duration of the common cold in adults. Still, it would be a leap of faith to think it does the same for COVID-19, and too much zinc can reduce immune activity. The upper limit for safety seems to be around 150 milligrams per day.

People who get large amounts of zinc also risk a copper deficiency since zinc and copper bind to the same receptors in the digestive tract. Therefore, too much zinc can reduce copper absorption and lead to a copper deficiency. Also, avoid using zinc preparations that you use intranasally as they have been linked with permanent loss of smell.

At the very least, you don’t want to be deficient in zinc, considering the key role it plays in immune health. Make sure you’re eating enough zinc-rich foods, but I would stop short of recommending a zinc supplement at this point. However, it’s something to watch closely. Chloroquine and hydroxychloroquine definitely bear watching too. 

Vitamin D

sunlight as a source of vitamin D

Vitamin D is another hormone-like vitamin that helps balance the immune system, among other roles. Ramping up the immune response is of interest when you’re dealing with viruses. So, it’s not surprising that scientists wonder whether vitamin D might protect against coronavirus. Vitamin D comes in two forms: cholecalciferol (vitamin D3) and ergocalciferol (vitamin D2) Most supplements contain cholecalciferol, the D3 form.

Why the interest in vitamin D? Some studies show that vitamin D boosts the activity of immune cells called macrophages that fight viruses. What’s more, macrophages have receptors on their surface for vitamin D. That shows the key role vitamin D plays in fighting viruses.

As Michael F. Holick, MD, PhD, from the Boston University School of Medicine points out, vitamin D deficiency weakens the immune system and increases the risk of a viral illness. He also points out that having an adequate vitamin D level may reduce the risk of developing some respiratory infections, including influenza type A. But, as you know, COVID-19 is not influenza and you can’t extrapolate from influenza to a novel virus we don’t yet understand.

With these points in mind, I still think it’s important to maintain a healthy vitamin D level and to supplement with vitamin D if you’re even somewhat low. If you don’t know your level, you can find out with a simple blood test your doctor can order. If you don’t want to check your level, it is safe for most people to consume 2000 I.U. each day, but check with your health care professional before taking a vitamin D supplement.

Vitamin C

Vitamin C Rich Foods

I just read that vitamin C sales are skyrocketing due to the COVID-19 pandemic, but are people wasting their money? Vitamin C is an antioxidant vitamin that, like vitamin D, you need for a healthy immune system, but is it the miracle supplement that some people claim?

You might be familiar with the claims made by Dr. Linus Pauling that vitamin C cures the common cold. Although studies don’t support the idea that vitamin C is curative, some research shows that taking vitamin C when you first catch a cold can shorten its duration by a day or so. In one study, vitamin C supplements reduced the time to recovery by 14% in children and 8% in adults. Plus, vitamin C may also make the symptoms a little more tolerable. Plus, one study found that vitamin C slashed the risk of catching a cold by 50%, but only in athletes.

The downside is we don’t know how vitamin C affects COVID-19. Researchers in China carried out a study where they gave very high doses of vitamin C intravenously to COVID-19 patients. Other patients received a placebo. The doses they used were over 12 times the recommended daily intake. Unfortunately, the study hasn’t ended yet, so we don’t know the outcome. But if it helps, the benefit is likely modest.

One problem with taking vitamin C as an oral supplement is how it’s absorbed. The recommended daily intake of vitamin C for men and women is 90 milligrams and 75 milligrams respectively. Sources recommend taking up to 1,000 milligrams to protect against viruses. However, vitamin C absorption decreases as the quantity you take goes up. If you take 1,000 milligrams, you may only absorb about half that amount.

Plus, oral vitamin C at high doses can have side effects such as nausea, diarrhea, and bloating. In susceptible people, it can also boost the risk of kidney stones. Some naturopathic physicians superload vitamin C into the body by giving repeated injections through the veins. Doing this carries a high risk of oxalate accumulation in the kidneys which is harmful and can even be lethal.

Still, I would recommend getting more vitamin C from dietary sources and if you take a vitamin C supplement, check with your physician first.

Elderberry Syrup

Elderberry syrup for immune health

Elderberry syrup is popular during the influenza season, as some studies suggest it might reduce the severity of influenza and shorten its course. There was even a study showing elderberry extract was comparable to the anti-viral medication Tamiflu for easing the symptoms of influenza. However, COVID-19 isn’t an influenza virus, so we can’t draw conclusions about its effectiveness against coronaviruses. Taking elderberry syrup could give people a false sense of security and that’s dangerous. That’s true of any supplement. We don’t know that they work, so we have to depend on other measures like social distancing and handwashing to lower our risk.

If you take elderberry syrup, buy an approved syrup from a reputable manufacturer. Raw elderberries are toxic. Taking elderberry syrup probably won’t harm you and it may protect against influenza viruses, but don’t assume it will protect against COVID-19. We don’t have enough knowledge to say at this point.

Black Licorice

Black licorice

The black licorice you buy in the United States is mostly sugar and licorice flavoring, but European licorice contains an herb called glycyrrhizin, the sweet-tasting component of licorice root. Glycyrrhizin has anti-viral and anti-inflammatory properties. In fact, in Asian countries, health care professionals combine glycyrrhizin with anti-viral medications to treat conditions such as HIV and hepatitis as the combination is more effective than anti-virals medications alone.

Even more exciting is the fact that glycyrrhizin seems to reduce the replication of coronaviruses, including SARS-COV. Glycyrrhizin seems to have some immune-modulating benefits too. As with elderberry extract though, scientists haven’t looked at the impact glycyrrhizin has on COVID-19 and there would be concerns about using supplements with anti-inflammatory activity indiscriminately. Recent reports show that taking non-steroidal anti-inflammatory medications (NSAID) may worsen the symptoms of COVID-19 infection.

There’s another reason to be wary of glycyrrhizin. For one, higher doses can decrease testosterone and increase levels of cortisol, a stress hormone. Plus, glycyrrhizin acts at the kidney to increase sodium absorption and reduce potassium absorption. So, higher doses can cause a rise in blood pressure and an excess loss of potassium.

handwashing to prevent COVID-19

The Bottom Line

At this time, there are no supplements that are proven to prevent or treat COVID-19 infection. Remember, this is a new virus that our body doesn’t recognize and has had no experience with. A healthy immune system may help you fight it and zinc, vitamin C, and vitamin D support immune health. That’s why you should get enough of these vitamins and minerals in your diet.

Just as important, get enough sleep and manage stress. Both stress and lack of sleep increase the stress hormone cortisol and that decreases your body’s ability to fight viruses. However, I would recommend checking a vitamin D level and taking a vitamin D supplement if it’s not in the optimal range. Of course, there are also common-sense measures like washing your hands thoroughly (sing Happy Birthday while you scrub), social distancing, and eating a nutrient-dense diet. These are all common-sense measures that help lower our risk of catching other viruses. 

Also, stay positive! We’re in this together and will get through it. Remind yourself of everything you have to be thankful for every day. 


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Kristie Leong M.D.

Dr. Kristie Leong and Dr. Apollo Leong are physicians helping you to lead a healthy lifestyle by sharing nutrition and fitness tips and keeping you abreast of the latest health news.