The immune system’s army is marching on its stomach like any combat force. Around 70 percent of the force of the immune system is in the stomach and intestines. Warriors of the immune system need fine, daily nutrition including Greek yogurt, beans, and bananas. Scientists have long recognized that poor and undernourished people are more vulnerable to infectious diseases. However, it is not certain whether the increased rate of disease is due to the effect of malnutrition on the immune system. There are still very few studies of the effects of nutrition on the human immune system and far fewer studies that explicitly tie the effects of nutrition to disease development (as opposed to treatment).

There are studies of the effects of nutritional changes on the animals’ immune systems, but again there are few studies that address disease development in animals as a result of changes in immunity. For example, one group of researchers found that protein-deficient diets in mice both reduce the number and function of T-cells and macrophages and also reduce the production of immunoglobulin A (IgA) antibodies.

There is some evidence that various deficiencies of micronutrients — for example, deficiencies in zinc, selenium, iron, copper, folic acid, and vitamins A, B6, C, and E — alter animal immune responses as measured in the test tube. The impact of these changes in the immune system on animal health is less clear, however, and the effect of similar deficiencies on human immune response has yet to be assessed. But the research is promising at this stage, for at least some of the micronutrients.

How will you do then? If you believe that your diet doesn’t include enough of your micronutrient needs — maybe you don’t like vegetables or prefer white bread over whole grains — taking a regular multivitamin and mineral supplement provides other forms of health benefits beyond any possible beneficial effects on the immune system. Single-vitamin megadose vitamin therapy corrects deficiencies. Needless to say, better is more. Researchers are studying the ability of various nutrients to strengthen immune functions.

Vitamin A. Experts have known for a long time that vitamin A plays a role in the infection and maintenance of mucosal surfaces by influencing certain subcategories of T cells, B cells, and cytokines. Deficiency of vitamin A is associated with reduced immunity and increased disease risk. On the other hand, supplementation in the absence of a deficiency according to one study did not improve or suppress T cell immunity in a group of healthy seniors.

Vitamin B2. There is some evidence that vitamin B2 increases resistance to bacterial infections in mice, but it is unclear what that means in terms of increasing immune response

Vitamin B6. Several studies have suggested that a vitamin B6 deficiency can depress aspects of the immune response, such as lymphocytes’ ability to mature and spin off into various types of T and B cells. Supplementing with moderate doses to address the deficiency restores immune function, but megadoses don’t produce additional benefits. And B6 may promote the growth of tumors.

Vitamin C. The jury is still out on the immune system and the vitamin C. In general, several studies have looked at vitamin C; unfortunately, several of them were not well planned. Vitamin C may function in combination with other micronutrients rather than bringing benefits on its own. Vitamin C is thought to be helping to reverse some of the damage COVID-19 can do, especially in the form of an intravenous (IV) infusion. There’s no evidence it can cure or treat coronavirus. Since the novel coronavirus is new it is not completely known by physicians. Both possible therapies remain uncertain, and vitamin C has not yet been evaluated or proven to be able to cure the virus. There is no evidence that taking vitamin C is harmful to people with COVID-19, but there is also no evidence that the virus can be cured or slowed. Scientists are studying injections of high-dose IV vitamin C, not over-the-counter supplements.

Vitamin D. The interplay between viral infections and vitamin D remains an intriguing concept, and the global imprint that vitamin D can have on the immune signature in the context of viral infections is an area of growing interest. The current coronavirus pandemic has some searching for ways to keep their immune systems in tip-top shape and there is evidence that vitamin D can support precisely this. Evidence that vitamin D supplements reduce the risk of developing COVID-19 is lacking, but having healthy vitamin D levels can improve immune health. Low levels of vitamin D are associated with an increased risk of respiratory diseases including tuberculosis, asthma, chronic obstructive pulmonary disease (COPD), and viral and bacterial respiratory infections. Supplementation with vitamin D reduces the risk of serious asthma exacerbations usually precipitated by viral upper respiratory tract infections.

Vitamin E. A research involving healthy subjects over the age of 65 showed that increasing the daily dose of vitamin E from the recommended dietary allowance (RDA) from 30 mg to 200 mg improved antibody response after vaccination to hepatitis B and tetanus. However, after administration of diphtheria and pneumococcal vaccines, such enhanced responses did not occur.

Selenium. Some studies have suggested that people with low levels of selenium are at greater risk of cancer of the bladder, breast, colon, rectum, lung, and prostate. A large-scale, multi-year study is underway to examine the effects of combining selenium and vitamin E on the prevention of prostate cancer.

Zinc. Zinc is an important trace element for immune system cells and deficiency of zinc affects the ability of T cells and other immune cells to function as they should. Caution: While it’s important to have enough zinc in your diet (15–25 mg daily), too much zinc may inhibit the immune system function.

The content of this post is provided for informational purposes only and is not intended as medical advice, or as a substitute for the medical advice of your physician.