Does Diet Affect Risk of Infection?

Does Diet Affect Risk of Infection?

By Nasira Burkholder-Cooley, DrPH, RDN


In order to stay healthy, it is necessary to avoid exposure to disease and practice preventive hygiene like handwashing. Additionally, maintaining a strong immune system is crucial for defending against infection, and nutrition undoubtedly supports immune function. Amidst the current coronavirus pandemic, it’s relevant to consider what specific nutrients may play a role in fighting a disease like COVID-19. Research is limited on natural remedies specifically for coronavirus, but there is information indicating positive effects of various vitamins and minerals for the prevention of infectious illnesses.

Vitamin C is necessary for white blood cell function and enhances iron absorption. Iron deficiency is fairly common, particularly among women and plant-based eaters, and inadequate levels can increase susceptibility to infection. While adequate vitamin C intake is important for immune function, mega-doses can lead to adverse side effects, such as upset stomach, diarrhea, and interference with medications. Rather than taking a vitamin C supplement, consider consuming whole food sources such as kiwi, citrus, bell peppers, berries, strawberries and Brussel’s sprouts.

Zinc has anti-viral properties and certain zinc supplements have been shown to reduce the severity and duration of colds (3). Laboratory studies suggest increasing intracellular zinc concentration can impair the replication of a variety of viruses, including influenza and SARS- CoV. Zinc may not prevent infection entirely, but adequate intake supports immune function. Keep in mind that excessive supplementation with zinc may interfere with absorption of the essential mineral copper, so limit use of zinc lozenges to once a week. Natural sources of zinc include legumes, nuts, whole grains, seeds, meat and shellfish.

Vitamin D is found in dairy products, egg yolks, and fatty fish, like salmon. Another source of vitamin D is exposure to sunlight – just 10 to 15 minutes of sunshine on the arms and legs each week can generate enough vitamin D to meet most adults’ needs. For individuals living in Northern parts of the world, sun exposure may not be adequate to synthesize enough vitamin D, so a vitamin D supplement may be appropriate to maintain optimal health. Research demonstrates that in people who are vitamin D deficient, adding a moderate vitamin D supplement may reduce the risk of respiratory infection (1).

N-Acetyl Cysteine (NAC) is the supplemental form of cysteine, an amino acid found in protein- rich foods like pork. NAC is needed to regenerate glutathione, an important antioxidant that serves to prevent cellular damage. A clinical study demonstrated that twice daily
supplementation with NAC reduced symptoms in people with the flu (2).

Polyphenol compounds are found in a variety of plant foods and are especially rich in deeply pigmented fruits, such as elderberries. Black elder has been used for centuries as a treatment for viruses and is one of the most popular medicinal plants worldwide. Some preliminary research suggests that elderberry extract may reduce the duration of the flu.

Look to reputable resources for reliable information on COVID-19.

For more information about COVID-19, check out the Centers for Disease Control and  the
World Health Organization’s Myth Busters

1. Carlos A. Camargo, Davaasambuu Ganmaa, A. Lindsay Frazier, Franca F. Kirchberg,
Jennifer J. Stuart, Ken Kleinman, Nyamjav Sumberzul and Janet W. Rich-Edwards.
Randomized Trial of Vitamin D Supplementation and Risk of Acute Respiratory
Infection in Mongolia. Pediatrics September 2012,  130 (3) e561-e567; DOI:
2. De Flora S1, Grassi C, Carati L. Attenuation of influenza-like symptomatology and
improvement of cell-mediated immunity with long-term N-acetylcysteine treatment.  Eur
Respir J. 1997 Jul;10(7):1535-41.
3. Hemilä, H., Chalker, E. The effectiveness of high dose zinc acetate lozenges on various
common cold symptoms: a meta-analysis. BMC Fam Pract 16, 24 (2015).