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Can You Boost Your Resistance to COVID-19?

Adequate sleep and taking several specific supplements could help you boost your resistance to infection. Don't overlook the probiotics.

COVID-19 has infected more than 100 million people around the world and killed more than 2.2 million. In the US, those figures are currently 26 million infected with more than 442,000 deaths. You know that trying to avoid infection calls for maintaining physical distance between yourself and people outside your household. In addition, you have read about washing your hands and wearing a mask in public. There is not yet a vaccine and there are no medications that have been shown to work against this disease. But are there any other ways you could boost your resistance to COVID-19?

Improve Your Immunity to Boost Your Resistance:

We like the idea of taking a general approach to improving immunity. Not only could this help you resist COVID-19 infection or potentially make it less serious, it could also lower your likelihood of catching a cold or the flu.

A large number of people who have been tested for COVID-19 got negative results, but they presumably had something that was making them feel ill. Avoiding symptoms that require medical care would also cut down on your chance of encountering another patient with COVID-19.

That’s why we like the suggestions from pulmonologist Roger Seheult, MD. Since late January, he has been providing clear, accessible updates on the medical information about COVID-19 at www.MedCram.com

In Update 59, Dr. Seheult offers practical information on what he is doing to bolster his resistance. He is seeing patients who test positive for the coronavirus. He cautions that he is describing his personal regimen, not recommending supplements or activities for others. Nonetheless, we think his suggestions are on target. They correspond well to research we have seen on how to improve immunity.

Vitamin C:

Vitamin C is extremely important for the proper function of the immune system. It has beneficial effects on the lungs, in particular. No one knows whether vitamin C supplements could help boost your resistance to COVID-19. However, research indicates that vitamin C can improve immune function and help prevent respiratory and systemic infections (Nutrients, Nov. 3, 2017). It takes 100 to 200 mg daily to achieve this goal.

We recently got this question from a reader who can’t get vitamin C from orange or grapefruit juice.

Q. I can’t tolerate citrus. Even a sip of orange juice upsets my digestive tract. I fear I may not be getting enough vitamin C from my diet.

I frequently get long bouts of bronchitis during the winter. COVID-19 has me worried. Should I be taking vitamin C and if so, how much? Are there any other vitamins that might be helpful for my immune system?

A. Since you avoid citrus fruit, you may well wish to consider an ascorbic acid (vitamin C) supplement. One study compared vitamin C to azithromycin for treating acute bronchitis (Lancet, May 11, 2002).  They worked equally well. However, bacteria will not develop resistance to vitamin C, so far as we know.

There is some suggestion that vitamin C, vitamin D and zinc may all be helpful in enhancing the immune response to COVID-19. Although high-quality studies have not yet been published, clinicians at the Cleveland Clinic have described the potential benefits of such supplements (Cleveland Clinic Journal of Medicine, June 8, 2020). 

They write:

“Because of their potential to influence immune response, ascorbic acid (vitamin C), zinc, vitamin D, and N-acetylcysteine [NAC] have been hypothesized to be useful for prevention or treatment of COVID-19.”

You can learn much more about these vitamins and zinc, including sources, doses and anticipated benefits in a book by Dr. Tieraona Low Dog, Fortify Your Life: Your Guide to Vitamins, Minerals, and More

Vitamin D:

Another really important vitamin for maintaining good immune function is vitamin D. Dr. Seheult cites a meta-analysis published in 2017 showing that vitamin D supplementation can help prevent acute respiratory tract infections (BMJ, Feb. 15, 2017). Daily vitamin D supplements worked better than big doses of vitamin D given once a month or once a quarter. Not surprisingly, people who were deficient in vitamin D got the greatest benefit.

Dr. Seheult takes 2500 IU/day. The RDA is 600 IU/day for people under 70 and 800 IU/day for those 71 and older. Other physicians are also looking at the possibility that vitamin D could help people fight off COVID-19 infection (American Journal of Physiology. Endocrinology and Metabolism, May 1, 2020). You can read more about vitamin D to help boost your resistance to COVID-19 here.


You were probably already familiar with vitamin C and vitamin D. You may well be taking them yourself as part of your own vitamin regimen. But the next supplement Dr. Seheult is taking might surprise you. Quercetin is a plant compound called a flavonoid. This compound is a “zinc ionophore”–it opens a special “door” or “gate” in the cell membrane so that zinc can get into the cells. This may help boost your resistance to the SARS-CoV-2 virus at the cellular level, although that is still unproven. The usual dose is 500 mg twice a day.


Another supplement that may not yet be on your radar is N-acetylcysteine (NAC). Italian researchers gave people NAC at a dose of 600 mg twice daily for six months (European Respiratory Journal, July 1997). During the influenza season, those taking NAC had much less severe symptoms than those on placebo. Moreover, elderly, high-risk individuals got the greatest benefit. These are precisely the individuals most at risk from COVID-19 as well.

Other researchers have suggested that nutraceuticals including NAC may boost the immune system’s interferon response to RNA viruses like SARS-CoV-2 (Progress in Cardiovascular Diseases, Feb. 12, 2020).  During the swine flu epidemic, NAC reduced pulmonary inflammation and pulmonary edema in laboratory animals (International Immunopharmacology, Sep. 2014). We don’t know if it will provide humans similar protection from COVID-19.


Zinc can help boost your resistance to infection because it is a gatekeeper of immune function (Nutrients, Nov. 25, 2017). Dr. Seheult takes 50 mg/day when he expects he may be exposed to COVID-19 in his work. That dose is too high to take on a regular basis, however. Chronically high doses of zinc can interfere with proper copper absorption and metabolism. Consequently, people should not usually take more than 40 mg daily. That’s the tolerable upper limit for adults.


Now, it isn’t a supplement. In fact, sleep is more like a foundation for good health. In addition to being a pulmonologist, Dr. Seheult is a critical care physician and a sleep specialist. That may be why he stresses the importance of getting seven to eight hours of sleep a night. Research has shown that getting adequate sleep during an infection helps boost your resistance to it (Physiological Reviews, July 1, 2019). In addition, a strong immune system also helps you sleep better.


Dr. Seheult doesn’t mention probiotics. However, there is evidence that probiotic consumption can enhance the immune system response (Annals of Nutrition & Metabolism, Jan. 23, 2019). The appropriate probiotic can activate regulatory T cells and help the innate immune response.

In addition, although we generally think of COVID-19 as affecting the lungs, many people have digestive tract symptoms associated with the infection. Frequently, scientists can detect SARS-CoV-2 in the stool of infected patients (Gut, April 9, 2020). 

Investigators have found that probiotics (beneficial bacteria) and paraprobiotics (sterilized probiotics) can boost your resistance to viral infection, especially RNA viruses (Current Pharmaceutical Design, 2018). SARS-CoV-2 is an RNA virus, so while we don’t have the evidence that probiotics can help protect you from COVID-19, there is reason to expect that strains such as Lactobacillus rhamnosus (LGG) and Lactobacillus plantarum L-137 might be beneficial.

Where would you find a probiotic that you could trust? We have confidence in the MultiBac product from our underwriter, KayaBiotics.com. This company has paid close attention to the complex science of probiotic supplementation.

KayaBiotic products are made in Germany, where oversight of good manufacturing practice is far more stringent than in the US. In addition, all of the ingredients that go into this probiotic product are organic. Consequently, that is the probiotic that we choose. Here is a link to KayaBiotics.com. You can save $10 when you put PEOPLE in the promo code. 

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About the Author
Terry Graedon, PhD, is a medical anthropologist and co-host of The People’s Pharmacy radio show, co-author of The People’s Pharmacy syndicated newspaper columns and numerous books, and co-founder of The People’s Pharmacy website. Terry taught in the Duke University School of Nursing and was an adjunct assistant professor in the Department of Anthropology. She is a Fellow of the Society of Applied Anthropology. Terry is one of the country's leading authorities on the science behind folk remedies..
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