“Immune Boosting” Nutrition Fact Check

There is a lot of information floating around right now promoting different nutrients and products as ‘immune boosting’ in response to COVID-19. Some of this information is valid, while some of it is not. While there are nutrients that support the body’s immune response and help to regulate inflammation, unfortunately nutrition alone is not a substitute for infection prevention measures like physical distancing and hand hygiene. During this time, it is important to maintain adequate nutrition, continue with regimens set forth by you and your healthcare team, and practice self care (whatever that might look like for you). To help navigate the information in the media, the following outlines specific nutrients and their relation to immune function + food sources for those nutrients.


Vitamin C (1,2): vitamin C or ascorbic acid serves many functions in the body. It serves as an antioxidant, protecting the body against inflammation and free radicals and aids in the synthesis of collagen. Vitamin C also assists with absorption of iron- which is needed to help the body transport oxygen to cells. These roles are important in the immune response, as the formation of collagen helps to provide a barrier against pathogens via skin and other tissues. When an infection occurs, whether via a virus or bacteria, an acute inflammatory response is triggered. This response helps to fight the virus, but in some cases the inflammatory response exceeds the need and can cause damage. Vitamin C, as an antioxidant can help to control that excessive inflammatory response. While the media may tout the, “the more the merrier” mentality, when it comes to vitamin C, that is not true. The body regulates levels of vitamin C, excreting excess in the urine. Taking too much via supplements can put extra stress on the kidneys. Instead of taking supplements, simply add some red bell pepper or a couple clementines to a meal or a snack to meet the recommended dietary allowance for adults. Other strong sources of vitamin C include citrus fruits, green bell peppers, strawberries, brussel sprouts, and broccoli. While deficiency of vitamin C may hinder the immune response, there is a lack of evidence to support extra vitamin C to ‘enhance’ immune function when intakes are adequate.


Vitamin D (3,4): vitamin D is important in the metabolism and maintenance of calcium and phosphorus in the body, but has become a big vitamin of interest in many disease processes. When it comes to immune function, vitamin D also serves a role in mediation and mitigation of the strong inflammatory response that can occur with infection. Vitamin D has been noted to decrease B cell and T cell production (slowing down the immune response) and decreasing the inflammatory cytokines (IL-6, TNF alpha) which are frequently targeted in critical illness. Like many other vitamins, while there may be a connection between vitamin D deficiency and decreased immune function, there is a lack of evidence to support vitamin D supplementation if intakes are adequate. Good sources of vitamin D include fatty fish like salmon, mushrooms, and fortified milk. Additional vitamin D can be obtained via the sun, about 15 minutes in the middle of the day has been recognized as adequate. If you are known to be deficient, discuss your supplementation regimen with your healthcare team and remember that vitamin D is a fat-soluble vitamin meaning that it requires fat for absorption so it is best to take it with a meal (and enzymes if you are pancreatic insufficient).


Zinc (5,6): Zinc is a mineral that functions in many enzymatic reactions in the body, aids in wound healing/tissue regeneration, and is recognized for its role in immune function. This role in immune function is related to zinc’s function with neutrophils, B and T cells as well as their role in DNA and RNA replication and transcription respectively. Zinc has been studied in relation to many infectious diseases, including the common cold in which supplementation may decrease the severity and duration of symptoms. At this time, there is no data to suggest a benefit in taking zinc in regard to COVID-19. Like vitamin C and vitamin D, there is limited evidence to support the supplementation of zinc to “boost” immunity, but rather that deficiency of zinc can hinder the vital functions it plays, so it is important to make sure intakes are adequate. Beef, beans, nuts, and fortified breakfast cereals are prominent sources of zinc. If there is concern about deficiency, discuss ways to optimize intakes with your care team.


This information does not serve as medical advice. Please contact your healthcare team if you have immediate or specific healthcare concerns.


References Links:


  1. https://ods.od.nih.gov/factsheets/VitaminC-HealthProfessional/

  2. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5707683/

  3. https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/

  4. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3166406/

  5. https://ods.od.nih.gov/factsheets/Zinc-HealthProfessional/

  6. https://academic.oup.com/ajcn/article/68/2/447S/4648668

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