There is no doubt that nutrition is an essential part of a strong immune system. Food provides the vitamins and minerals necessary for the production of immune cells, enzymes, and cofactors that allow your body to combat illness. Deficiency in various nutrients, including vitamin C and D, have been linked to increased risk of infection and poorer outcome following an illness.
Despite this, nutritional strategies to support optimal immune function are often missing in public health discussions around the coronavirus and other common illnesses, such as influenza. A recent paper from a group of leading researchers out of Oregon State and other worldwide universities proposed a clear set of nutritional recommendations to complement messaging about the role of hand washing and vaccinations in virus protection.
The authors highlight the fact that although healthy, high-quality food is essential for wellness and immune function, supplementation is often warranted and can have a protective effect.
Protective Immune Nutrients
Every stage of the immune response is reliant on the presence of certain micronutrients:
Vitamin C increases pathogen-killing immune cells and antibody production while donating electrons to lower oxidative stress.
Zinc enhances activity of immune cells, reduces viral replication, and supports production of enzymes that scavenge-inflammation causing free radicals.
Vitamin A enhances immune cells and acts as an antioxidant to help maintain the body’s physical barriers against pathogens.
Vitamin D raises levels of immune cells and helps regulate the immune response so that inflammatory markers don’t get out of control and damage cells.
Vitamin E is an antioxidant that improves activity of various immune cells, including natural killer cells and B and T cells.
Vitamins B6, B9, and B12 enhance NK immune cells and support the gut barrier against the invasion of pathogens into the blood stream.
Iron is essential for the growth of epithelial tissue that serves as a barrier to invading pathogens.
Copper increases NK immune cells and is a catalyst for helping the body fight inflammation.
Selenium is used in enzymes that are critical for the body’s antioxidant defense system, supporting NK immune cells.
Magnesium regulates immune cell activation and is involved in tissue and DNA repair.
Omega-3 Fatty Acids support immune function by helping the body resolve inflammation.
Many people aren’t eating enough of these nutrients, which can lower your resistance to infections. The following graph from the 2010 NHANES survey found that adults didn’t come close to meeting the Recommended Daily Allowance (RDA) for many of the 21 most important micronutrients for health and immunity. Deficiencies were above 80 percent for vitamin D, vitamin E, potassium, and over 50 percent for choline, potassium, and magnesium.
Is The RDA Even Sufficient?
It’s important to know that the RDA may not be sufficient to protect you from disease. The RDA is the average daily intake level that is necessary to avoid clinical or subclinical deficiency in 97 percent of the healthy general population. Although these recommendations can act as a baseline, they do not indicate the levels required to optimize immune protection and resistance to infection.
For example, in the case of vitamin C, the RDA in the U.S. is 75 mg for women and 90 mg for men. However, protection against infection requires dietary vitamin C intakes of 100–200 mg/day to provide optimize cell and tissue levels (2).
Treatment of established infections requires even higher doses, possibly around 6 g/day (5), to compensate for the increased inflammatory response and metabolic demand (2).
Another example is selenium: The RDA is 55 mcg in adults, however, studies show that supplementation with closer to 200 μg a day (6) can be used as therapy in viral infections such as the flu (7).
A significant body of work suggests that the RDA for vitamin D is unlikely to raise serum levels needed for adequate function of the immune system (4, 8).
It is important to know whether your body is able to effectively use the micronutrients you are getting from food. For example, it is well known that the bioavailability of trace elements such as iron, zinc, or magnesium in a plant-based diet is low (3).
Finally, many people have increased nutrient requirements due to factors that go beyond whether they are eating nutritious meals:
- Dietary choices such as vegetarianism raise nutrient needs.
- GI disorder such as irritable bowel and celiac disease reduce absorption of nutrients.
- Stress, lack of sleep, and intense exercise all increase need for antioxidants and magnesium to help repair DNA.
- Genetics and certain health conditions like diabetes and obesity exacerbate nutrient requirements for immunity and health.
- The body may also lose micronutrients when exposed to pathogens, which causes the immune system to become increasingly active (1). An active infection depletes the body of vitamins A, C, and E, calcium, zinc, and iron, and levels only return to normal once symptoms improve (9).
Immune Support Recommendations
Because many nutrients are involved in immune function, the study authors recommend taking a high-quality multi-micronutrient supplement (https://main.poliquinstore.com/core-essentials) that supplies 100 percent of the U.S. RDA for vitamins and trace elements including vitamins A, B6, B9, B12, zinc, iron, selenium, magnesium, and copper.
They also recommend daily intake of the following for optimal immune function:
Vitamin C: Daily intake of at least 200 mg for healthy individuals. If you are sick, 1 to 2 grams a day is recommended.
Vitamin D: Daily intake of 2,000 IUs or 50 ugs.
1. Calder, P., et al. Optimal Nutritional Status for a Well-Functioning Immune System Is an Important Factor to Protect against Viral Infections. Nutrients. 2020. 12, 1181.
2. Carr, A., Maggini, S. Vitamin C and immune function. Nutrients. 2017. 9, 1211.
3. Gombart, A., et al. A Review of Micronutrients and the Immune System–Working in Harmony to Reduce the Risk of Infection. Nutrients. 2020. 12, 236.
4. Hewison M. An update on vitamin D and human immunity. Clinical Endocrinology. 2012. 76, 315-325.
5. Hume, R., Weyers, E. Changes in leucocyte ascorbic acid during the common cold. Scottish Medical Journal. 1973. 18(1), 183–7.
6. IOM (Institute of Medicine). Dietary Reference Intakes for Calcium and Vitamin D. The National Academies Press: Washington, DC. 2011.
7. Steinbrenner, H., et al. Dietary selenium in adjuvant therapy of viral and bacterial infections. Advanced Nutrition. 2015. 6, 73–82.
8. Wimalawansa, S. Vitamin D in the new millennium. Current Osteoporosis Reports. 2012. 10, 4–15.
9. Wishart, K. Increased micronutrient requirements during physiologically demanding situations: Review of the current evidence. Vitamins and Minerals. 2017. 6, 1–16.