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NMU 155 – Nutrition and Immune Function

Nutrition / Natural Medicine Update No 155 (March 15, 2020)

with Dr. James Meschino


Topic: Nutrition and the Immune System

Source: Multiple Peer-Reviewed Journal Articles


In this Lifestyle Medicine Update, I would like to explain the scientific understanding we have on how nutrition and nutritional medicine supports our immune system function. Preventing viral-induced respiratory tract infections largely depends on how efficient your immune system is, and should you develop a virally-induced respiratory infection having an immune system that is working more optimally can help to prevent the infection from becoming more severe or virulent. All experts agree that a decline or weakening in immune function makes us more susceptible to respiratory tract infections and allows these infections to become more severe and life-threatening. There is a decline in immune system function as we age and this why the elderly and people with compromised immune systems are more susceptible to life-threatening respiratory tract infections. But there are a host of things that can weaken the immune system. By the same token, some key nutritional factors can help strengthen and optimize our immune function. So, let’s examine both aspects:

These are the factors known to weaken our immune system

1. Aging (after 55-60 yrs.) – Immune system function declines with age:

A. Thymus gland undergoes involution with aging – (T-cell lymphocyte dysfunction)

B. Free radical damage accumulates, which damages immune cells and leads to immunosuppression (This can be slowed and/or reversed to some degree with the use of certain antioxidant supplements as you will see)

2. Decreased respiratory bursts (HOOH) neutrophils by age 60 (higher amounts of vitamin C intake has been shown to help neutrophils recover some of this capability as we will see later)

3. Drugs: corticosteroids (Prednisone), TNF-inhibitors for autoimmune disease (i.e. Humira, Remicade), anti-rejection drugs used by transplant patients (i.e. Cyclosporin)

4. Compromised Immune States: e.g. HIV-infection, Overtraining with your workouts, Diabetes, etc.

5. Depression and Stress:  feeling hopeless, high cortisol, etc.

6. Nutritional Deficiencies (we will examine these in detail shortly)


So, What Can You Do to Maintain a Strong Immune System?

1. Get enough sleep- your immune system recharges during sleep.

2. Don’t over-train – light to moderate exercise strengthens immunity, but overexertion and over-training weakens immunity, even in high-performance athletes – (more URTI)


Where Does Nutrition and Nutritional Medicine Fit into The Story?

Key Nutritional Factors Known to Impact Immune Function:

Antioxidants and Other Vitamins and Minerals

  1. Immune cells have a high requirement for antioxidants – especially vitamin C and vitamin E, and Beta-caroteneAhey Use These Antioxidants to Generate Free Radicals (ROS), which kill viruses and other microbes
  1. Immune Cells also use Antioxidants to Protect themselves against the ROS they produce. With suboptimal antioxidant status, immune cells cannot kill viruses as effectively and they cannot protect themselves from the ROS they generate. The high ROS levels, in turn, damages immune cells and they become less effective or immunosuppressed. As an example, a 2017 study reviewed all the available studies looking at the role of vitamin C on the immune system. The researchers cited the research showing that the ingestion of 250 mg per day of vitamin C in otherwise healthy people helps to enhance many important aspects of immune function. The goal is to achieve a vitamin C blood level above 50 umol/L, which most healthy people can achieve with a daily intake of 100-250 mg of vitamin C per day. This is can be very difficult to do from food alone and thus, vitamin C supplementation is an important consideration in achieving and maintaining optimal vitamin C status and immune function over our lifetime. As we get older and immune function declines, some studies suggest that the combination of 1,000 mg vitamin C per day and 200 IU of vitamin E per day improves immune function in people over 60. So higher doses are required as we age. Studies also show that when fighting the common cold supplementation with 200 mg per day of vitamin C can help reduce severity and duration, and the incidence of the common cold if we are also exposed to physical stress. This level of vitamin C intake may also reduce the common cold frequency in those who previously had lower vitamin C blood levels (below 45 umol/L).  Very importantly, higher levels of intake (1,000 mg vitamin C per day) has been shown to prevent the decline in vitamin C depletion within white blood cells during an infection.

And here is a quote from the research paper itself regarding lung infections, pneumonia, and vitamin C, “Beneficial effects of vitamin C on recovery have been noted in pneumonia. In elderly people hospitalized because of pneumonia, who were determined to have very low vitamin C levels, the administration of vitamin C reduced the respiratory symptom score in the more severe patients. In other pneumonia patients, low-dose vitamin C (250 – 800 mg/day) reduced the hospital stay by 19% compared with no vitamin C supplementation, whereas the higher-dose group (500 – 1600 mg/day) reduced the duration (hospital stay) by 36%. Vitamin C supplementation also showed a positive effect on the normalization of chest X-ray, temperature, and erythrocyte sedimentation rate (a marker of inflammation and infection). Since prophylactic vitamin C administration also appears to decrease the risk of developing more serious respiratory infections, such as pneumonia, it is likely that the low vitamin C levels observed during respiratory infections are both a cause and a consequence of the disease.”

This means that during an infection vitamin C turnover occurs more rapidly as immune cells draw down on their vitamin C stores to fight the infection. As vitamin C becomes more and more depleted within immune cells they become less and less effective, allowing more serious infections like pneumonia to take hold and progress. As the researchers so aptly concluded, “Thus, it is apparent that vitamin C is necessary for the immune system to mount and sustain an adequate response against pathogens, whilst avoiding excessive damage to the host. “

(Reference 1)

But other antioxidants have also been shown to be critical to immune function. For example, supplementation of healthy individuals over 60 with 200 IU vitamin E per day improved many aspects of immune function and reversed some key age-related features of immune system decline.  In short, they had a more youthful immune function with vitamin E supplementation. Supplementation with other nutrients has also shown improved immune function in human subjects, including zinc and beta-carotene. As well, animal studies show the importance of selenium to immune function. A number of researchers have conducted research providing healthy elderly individuals with supplement combinations such as Vitamin A, Vitamin C, and Vitamin E, or provided them with a multiple vitamin/trace mineral supplement. In each study, the participants ingesting the supplements showed the improved function of many immune parameters compared to their baseline values and compared to those who ingested the placebo

(Reference 2)

Moreover, human and animal studies have proven that even marginal deficiencies of certain vitamins and minerals cause a significant decline in immune function or immunocompetence. These nutrients include vitamin A, beta-carotene, folic acid, vitamin B6, vitamin B12, vitamin C, vitamin E, riboflavin, iron, zinc, and selenium. The NHANES surveys show that many people are walking around with marginal deficiencies of some of these nutrients unless they are taking a well-formulated multiple vitamin and mineral supplement

(Reference 3)

Herbal Agents

In addition to vitamins and minerals, certain herbal products have also been shown to have proven immune-modulating properties of importance. The ones I like best Astragalus, Medicinal Mushrooms like Reishi mushroom extract, Milk Thistle and the Indole-3-carbinol.


1. Astragalus

The Memorial Sloan Kettering Cancer Centre website does a great job of summarizing the research on Astragalus. They cite the studies showing that the medicinal constituents in astragalus can boost immune system competency and exert direct antiviral effects.

(Reference 4)

A 2012 review of all astragalus studies showed the many ways that astragalus enhances immune system function, including boosting the release of interferon and interleukin-2 from key immune cells, which are well established strong boosters of immune function.

(Reference 5)


2. Reishi Mushroom Extract and other Medicinal Mushrooms (Shiitake, Maitake, Cordyceps, Trametes Versicolor Turkey Tail and others)

Medicinal mushrooms contain unique ingredients that not only stimulate immune cells to work more efficiently but in some cases, they have constituents that fit perfectly into immune cell receptors. The binding of these constituents to the immune cell receptor generates a response from the immune cell that heightens and greatly optimizes its ability to combat foreign viruses, bacterial and other dangerous cells.  I have provided a number of references at the end of this video, which explain in detail the immune-enhancing properties of medicinal mushrooms. As one of the researchers stated, “(Medicinal) Mushrooms have been shown to have the ability to stimulate the immune system, modulate humoral and cellular immunity, and potentiate antimutagenic and antitumorigenic activity, as well as rejuvenating the immune system weakened by radiotherapy and chemotherapy in cancer treatment”. (8)

(References 6-8)


3. Milk Thistle

The herb Milk thistle has also shown impressive immune-modulating properties in recent years. Milk thistle has primarily been used to support liver detoxification function and to help repair damaged liver cells if the damage is not beyond repair. But the silymarin flavonoid in Milk thistle has also been immunostimulatory. It increases lymphocyte proliferation – an important factor in preventing and fighting infections and it boosts secretions of immune-modulating chemicals or cytokines, particularly interferon-gamma, interleukin-4, and interleukin-10. These responses are required when the body is facing a virus that is trying to take hold and start an infection. The researchers state, “Our study has uncovered a novel effect of milk thistle on the immune system. This immunostimulatory effect may be of benefit in increasing the immunity to infectious diseases”. (9)

(Reference 9 and 10)


4. Indole-3-carbinol

Finally, I also like the research pertaining to the Indole-3-carbinol, which is a constituent unique to cruciferous vegetables, such as broccoli, brussels sprouts, cabbage, cauliflower, Bok choy, and turnips. Supplementation with indole-3-carbinol has been shown to activate the aryl hydrocarbon receptors on the adaptive immune system, which stimulates immune cells to better respond to and fight any virus or foreign cell that enters the body. More specifically, it helps the T-lymphocytes proliferate faster and improves the ability of other immune cells to ingest and devour any threatening viruses or bacteria that are deemed threatening to the body.

(References 11 and 12)

One word of caution is that for individuals with an autoimmune disease (5-7% of the population) and individuals on immunosuppressive drugs (mostly transplant patients), it may be unwise to supplement with the herbal agents I have spoken about here, as they may overstimulate the immune system and worsen the autoimmune condition or counteract the effects of immunosuppressive drugs. For most healthy adults, for the sake of immune system support, it may be wise to take a High Potency Multiple Vitamin and Mineral that is enriched with antioxidants (i.e. Vitamin C- 1000 mg, Vitamin E- 200-400 IU, Beta-carotene – 15,000 IU, Selenium – 200 mcg) As well, taking a supplement containing Astragalus, Reishi Mushroom Extract, Milk Thistle and Indole-3-carbinol may be another consideration.

Some people go further and ingest a teaspoon per day of a 14-mushroom blend powder, containing a mix of potent medicinal mushrooms. You may also want to consider a probiotic supplement, as a more optimal combination of friendly gut bacteria has also shown impressive immune-modulating properties in some studies.

I have included the scientific references for this information in the text below. I hope you find it enlightening and helpful



1. Carr A and Maggin S. Vitamin C and immune function. Nutrients. 2017 Nov.9(11):1211

2. Annals of Clinical & Laboratory Science, vol. 30, no. 2, 2000 145 Review: Free Radicals, Antioxidants, and the Immune System Joseph A. Knight Department of Pathology, University of Utah School of Medicine, Salt Lake City, Utah

3. Changes in the immune system are conditioned by nutrition. A Marcos1*, E Nova1 and A Montero1 1Grupo de Inmunonutricio ´n, Departamento de Metabolismo y Nutrition, Instituto del Frio (CSIC), Madrid, Spain

4. Memorial Sloan Kettering

5. Zhuge Z-Y, Zhu Y-H, Liu P-Q, Yan X-D, Yue Y, Weng X-G, et al. (2012) Effects of Astragalus Polysaccharide on Immune Responses of Porcine PBMC Stimulated with PRRSV or CSFV. PLoS ONE 7(1): e29320.

6. Alena G. Guggenheim, ND; Kirsten M. Wright, BS; Heather L. Zwickey, Ph.D. Immune Modulation From Five Major Mushrooms: Application to Integrative Oncology. Integrative Medicine Vol 13 No 1. February 2014

7. Cristina Lull,1 Harry J. Wichers,1 and Huub F. J. Savelkoul. Antin ammatory and Immunomodulating Properties of Fungal Metabolites. Mediators of Inflammation 2005: 63-80

8. Peter Amwoga Ayeka. Potential of Mushroom Compounds as Immunomodulators in Cancer Immunotherapy: A Review. Evidence-Based Complementary and Alternative Medicine Volume 2018 (9 pages)

9. Medicine and Science Monitor (2002)

10. American Surgery Journal (2002)

11. PHARMACOLOGICAL REVIEWS Pharmacol Rev 65:1148–1161, October 2013 Aryl Hydrocarbon Receptor Control of Adaptive Immunity



Eat Smart, Live Well, Look Great,

Dr. Meschino

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