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What foods may prevent COVID breakthrough infections and hospitalizations?

October 17, 2021 at 4:00 a.m.
Dr. Jamie Koonce shares a few foods that may help prevent COVID-19 breakthrough infections and hospitalizations. Submitted photo

Wearing an N95 or KN95 mask and getting a COVID-19 vaccine are safe and effective ways of preventing COVID-19, but because the transmission rate of the delta variant is still very high, some vaccinated individuals may still get a mild to moderate COVID-19 infection. However, some studies suggest that the foods you choose to eat or avoid may be able to prevent COVID breakthrough infections and hospitalizations.

Although public health messaging in the U.S. has omitted any nutritional recommendations for the prevention of breakthrough COVID-19 infections and severe symptoms, there is quite a bit of evidence that specific foods can either modulate immune system function or damage it.

Plant-based vs low-carb diets and COVID-19

One study on health care workers from six countries (France, Germany, Italy, Spain, USA, UK) with substantial exposure to COVID-19 patients during the summer of 2020 found that the overall dietary pattern of each health care worker played a huge role in whether they tested positive for COVID-19 during the study period as well as the severity of symptoms in those who did test positive.

Those following plant-based diets had 73% lower odds of experiencing respiratory symptoms, fever, or pneumonia, respiratory distress, oxygen levels below 93% saturation. Health care workers who ate a pescetarian diet had 59% lower odds of experiencing those same formerly mentioned moderate-to-severe symptoms. The plant-based dietary pattern and the pescetarian dietary pattern were both characterized as being higher in fruits, vegetables, beans and nuts, and lower in red meats, poultry, sugar-sweetened beverages, and alcohol.

One finding that might be shocking to some is that the health care workers who ate a low carbohydrate or high protein diet were more likely to be hospitalized with COVID-19 than health care workers who were not following a low carb or high protein diet. Healthcare workers who followed a low carbohydrate or high protein diet ate more eggs, poultry, and red meats, and avoided grains, fruits, and desserts.

Overall, this study suggests that increasing your intake of plant-based foods such as fruits, vegetables, beans, and nuts, and reducing your intake of red meat, poultry, sugar sweetened beverages, and alcohol, may be a good dietary strategy to help prevent severe COVID-19. But might particular plant-based foods confer more immune support than others?

Some research does suggest that this is the case.

Edible and medicinal mushrooms

Mushrooms, which technically are a type of fungus rather than a plant, are known to have a variety of antiviral and immunomodulatory properties.

Shiitake mushrooms can directly inactivate viruses as well as inhibit their replication, and this is an extremely important property to have considering that the reason the delta variant is so contagious is that it replicates so quickly in the upper respiratory tract.

In addition to inhibiting the ability of a virus to make copies of itself inside a host, shiitake mushrooms also downregulate the expression of proinflammatory cytokines such as TNF-α, IL-2 and IL-11 while upregulating anti-proliferative, antiviral, and immunomodulatory cytokines. In other words, shiitake mushrooms regulate your innate immune response, which is a critical factor for preventing severe COVID-19.

Hen-of-the-woods, also known as maitake, is another species of mushroom with strong antiviral effects. This nutrient-dense mushroom is high in beta-glucan, a beneficial polysaccharide that has been used therapeutically for cancer patients due to its anticancer potential. Hen-of-the-woods also contains an antiviral protein called GFAHP that has been found to inactivate herpes simplex virus and hepatitis B, as well as increase CD4+ cell count and sense of well-being in people living with HIV.

Another important mushroom is Ganoderma lucidum, or reishi. One study found that reishi mushroom combined with chlorella, a type of microalgae, downregulates inflammatory mediators such as TNF-α, cyclooxygenase-2, nuclear factor kappa-beta (κβ), and has a stronger antioxidant effect than the anti-inflammatory drug dexamethasone. This is interesting because dexamethasone has been shown to reduce mortality in patients hospitalized with COVID-19.

Chaga mushroom is known to reduce inflammation in the nose and throat, and has been used in traditional herbal medicine for centuries to facilitate breathing. Chaga's antiviral effects are comparable to Tamiflu when used to suppress influenza infections. One study found that Chaga mushroom acts on viral glycoproteins to prevent herpes simplex virus 1 from entering cells. In addition, beneficial polysaccharides in chaga have been found to inhibit JAK-STAT signaling pathways that can lead to the cytokine storm seen in COVID-19 patients with severe symptoms.

Shiitake mushrooms have a firm, meaty texture and are delicious marinated and stir-fried or grilled. Hen-of-the-woods is more delicate and can be eaten raw in a salad or cooked in soups and stews. Reishi and chaga are slightly bitter and woody and are typically consumed in the form of a tea, tincture, or powdered extract. You can purchase high quality reishi, chaga, and other medicinal mushrooms from the online store at

Pumpkin Everything

Besides mushrooms, other foods with antiviral effects include pumpkin, squash, zucchini, peas, beans, peanuts, eggplant, tomatoes, potatoes, and peppers. While these foods tend to be good sources of vitamin C, they're also high in proteins called plant cyclotides that have strong antiviral activity.

Fermented Foods

You may also consider adding at least one fermented food such as yogurt, kefir, filmjölk, kombucha, kvass, sauerkraut, natto, or kimchi to each meal. These foods contain a variety of beneficial bacteria that will improve your gut microbiome over time. This is especially important if you have ever used antibiotic medications. Improving your gut microbiome subsequently improves your lung microbiome, which helps to protect your lungs from viral infections.


A diet high in plants, mushrooms, and fermented foods has antiviral and anti-inflammatory properties that can make your body an unfriendly host for viral infections. For the most protection against COVID-19, influenza, RSV, and whatever else might be going around, you should incorporate antiviral and anti-inflammatory foods into your daily diet, but also make sure to get vaccinated. If you're eligible for a booster shot, go get that. And wear a mask if you're going to be sharing air with a bunch of other people. You wouldn't want to enter a sword fight with just a helmet, but no vest or sword. In this case, a mask is your helmet, the vaccine is your vest, and your nutrition is your sword.

Questions or comments? Email [email protected], or visit


Kim, HyunJu et al. "Plant-based diets, pescatarian diets and COVID-19 severity: a population-based case-control study in six countries." BMJ nutrition, prevention & health vol. 4,1 257-266. 7 Jun. 2021, doi:10.1136/bmjnph-2021-000272

Shahzad, Fanila et al. "The Antiviral, Anti-Inflammatory Effects of Natural Medicinal Herbs and Mushrooms and SARS-CoV-2 Infection." Nutrients vol. 12,9 2573. 25 Aug. 2020, doi:10.3390/nu12092573

Alkhatib, Ahmad. "Antiviral Functional Foods and Exercise Lifestyle Prevention of Coronavirus." Nutrients vol. 12,9 2633. 28 Aug. 2020, doi:10.3390/nu12092633

Self WH, Tenforde MW, Rhoads JP, et al. Comparative Effectiveness of Moderna, Pfizer-BioNTech, and Janssen (Johnson & Johnson) Vaccines in Preventing COVID-19 Hospitalizations Among Adults Without Immunocompromising Conditions -- United States, March -- August 2021. MMWR Morb Mortal Wkly Rep 2021;70:1337--1343. DOI: icon

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