Subscribe to Dr. Meschino’s Free Newsletter

Subscribe Now

NMU 156 – Nutrition and Immunity Part 2

Nutrition / Natural Medicine Update No 156 (March 20, 2020)

with Dr. James Meschino


Topic: Nutrition and the Immune Part 2

Source: Multiple Peer-Reviewed Journal Articles


This is part 2 of the two-part Nutrition and Immunity series. In part one I explained common ways in which our immune system becomes weakened, leaving us susceptible to respiratory tract viral and other infections. I also explained the research showing the impact of certain vitamins, minerals, and herbal agents, Astragalus, Medicinal Mushrooms, Milk Thistle, and Indole-3-Carbinol on supporting immune system function. In this part 2 video, I want to touch on three other nutrients showing promise in supporting immune system function, especially with respect to viral-induced respiratory tract infections. These include:

  1. Vitamin D
  2. Probiotics
  3. Melatonin (for those over 40-45 years of age)

Vitamin D

Let’s start with Vitamin D. An excellent review of how vitamin D works to strengthen the immune system against acute respiratory tract infections was published in the Journal of Infectious Diseases in 2010. These researchers performed a placebo-controlled double-blind study involving 164 young Finnish men (18-24 years of age) undergoing compulsory periodic military training. They showed that the men given 400 IU of vitamin D per day during the 6-month training period had significantly fewer respiratory tract infections and related fewer days of absenteeism from training compared to the recruits who ingested the placebo. There have been a number of vitamin D intervention trials like this, using vitamin D dosages as high as 4,000 IU per day.  Some studies have shown a protective effect against respiratory tract infections and some have not. What seems to be a fairly consistent finding is that individuals who have a blood vitamin D level above 80 nmol/L show greater resistance to upper respiratory tract infections and that those with low blood levels of vitamin D (especially blood levels below 25 nmol/L) appear to be at much higher risk. In this published paper the researchers explained a novel way in which vitamin D affects immunity with respect to the prevention of respiratory tract infections. They explain that immune cells that line the respiratory tract have vitamin D receptors, which allows vitamin D to enter these immune cells. Once inside the immune cell, Vitamin D is converted to a more potent form of vitamin D, which is then transported to the nucleus of the cell. Within the cell nucleus, vitamin D modulates specific genes involved in immunity. One of the gene effects is that vitamin D increases the secretion of a virus-killing molecule known as cathelicidin. As immune cells interact with various microbes, including viruses, in the respiratory tract, cathelicidin punctures a hole in the viral and/or bacterial cell membrane destroying the invader, and thus, preventing infection. As such, lower vitamin D blood levels result in lower secretions of cathelicidin with resulting in reduced anti-viral fighting abilities of the immune cells that line the respiratory tract. So, it is always a good idea to know your vitamin D blood level and to put into place supplementation practices, if necessary, to get your vitamin D blood level above 80 nmol/L (without exceeding 150 nmol/L) (or 32 – 60 ng/ml). Most people can achieve this with 600-2,000 IU per day of vitamin D supplementation if necessary.

Now some people need to be extra cautious with vitamin D supplements. These individuals include those with active tuberculosis, individuals with sarcoidosis (an autoimmune condition), lymphoma, and primary hyperparathyroidism. In each of these cases, the body is often synthesizing very high amounts of vitamin D as a result of the disease. Taking additional vitamin D can easily cause vitamin D toxicity. (vitamin D blood level at or above 250 nmol/L (100 ng/ml)

Reference No 1:

So, first, know your blood vitamin D level, and if it is below 80 nmol/L, then consider vitamin D supplementation to get it into the more ideal or optimal range (80-150nmol/L). (32 – 60 ng/ml). This is something to strongly consider in my view for a host of reasons, as vitamin D in the optimal range also helps support bone density, cardiovascular health and may be important in the prevention of some cancers as well as type 1 diabetes.

Reference No 2:



Okay, let’s talk about probiotics. According to the World Health Organization, “probiotics are live microorganisms that, when administered in adequate amounts, confer a health benefit on the host” (host = our human cells).

Reference No 3.

More specifically, probiotics are live microorganisms (specific strains of friendly gut bacteria and yeast) that may improve health by bolstering local and systemic immunity. (this immune function throughout the entire body). Their mechanism of action is thought to occur through enhanced phagocytic capacity and activity, stimulation of higher levels of specific immunoglobulins, and enhancement of gut barrier functions. This means that probiotics have been shown to boost the ability of certain immune cells to identify, engulf, and destroy many types of pathogens, including viruses that cause respiratory tract infections. It also means the probiotics have increased the levels of immunoglobulin A, which is a key antibody that protects the respiratory passages and the intestinal tract against infectious agents, including viruses.

Reference No.4

As outlined in a review paper in the journal Current Opinion in Gastroenterology, “probiotics showed therapeutic potential for diseases, including several immune response-related diseases, such as allergy, eczema, viral infection, and potentiating vaccination responses.” This means that probiotic supplements have in many cases toned down allergic sensitivities, improved cases of eczema – a skin condition often triggered by food or environmental allergies, intolerances or sensitivities, reduced viral infections, as we will discuss, and improves the efficacy of certain vaccinations, including the influenza vaccine. The researchers cite the studies showing that probiotics regulate our innate and adaptive immune responses by modulating the functions of dendritic cells, macrophages, and T and B lymphocytes. It’s the dendritic and macrophage immune cells that identify and gobble up viruses that are trying to invade the body, and our T and B-lymphocytes mount an antibody attack against viruses that are trying to infect us. So, the type of immune modulation we get from probiotic supplements may be an important consideration in optimizing immune function from day to-day.

Reference No. 5.

With respect to probiotics and upper respiratory tract infections, the Cochrane Review of 12 trials were included in a recent meta-analysis, and data from 3,720 participants in randomized controlled studies conducted between 2002 and 2013, involving eight different countries, were analyzed. The researchers concluded the following, “probiotics were found to be more effective than placebo—reducing the number of participants who experienced episodes of acute URTI by about 47% and the duration of an episode by about 1.89 days. Probiotics also slightly reduced antibiotic use and cold-related school absences. In older adults, although probiotics did not reduce the rate of URTIs, the duration of the infection was decreased. Subgroup analysis of all age groups suggests that probiotics reduced the number of children experiencing acute URTIs. Overall, probiotics were found to be safe with few adverse effects (mostly gastrointestinal symptoms).” These studies included a variety of different probiotic combinations, and thus, it is difficult to know what combination of live bacteria and yeast are the most ideal. In fact, no one knows, at this point in time, what the most ideal probiotic combination should be.

Reference No. 4

In the text below I have included the various lactobacillus, Bifidus, and streptococcal bacterial strains that show impressive probiotic results, along with the yeast species – Saccharomyces cerevisiae:

Complete List of Promising Probiotics:

  • Lactobacillus such as L. acidophilus, L rhamosus, rheuteri. L. plantarum. L casei. L. salivarius
  • Bifidobacterium, such as B. bifidum, B. animalis, B. breve, B. longum
  • Streptococcus thermophilus
  • The yeast species – Saccharomyces cerevisiae

Reference No 5.

So, you may want to take a probiotic supplement each day containing a good mixture of the impressive probiotic species I have outlined, in a form that delivers 2 – 10 billion living microorganisms per day.


Finally, I want to touch on the hormone melatonin. Melatonin is a hormone made by the pineal gland in the brain, but some immune cells also synthesize it. As we age melatonin secretion declines and this decline appears to be part of the reason that our immune function also declines in the aging process, a condition is known as immunosenescence.  Studies show that the T-lymphocyte known as the CD4 cell or the T-helper cell, which is the quarterback of the entire immune system, has melatonin receptors.  With a decline in melatonin levels in aging, there is less CD4 cell modulation by melatonin and the immune system becomes weaker and less efficient.  Experimental studies show that many immune parameters improve to more youthful function when melatonin is administered to aging animals. The same is likely true in humans.

Reference No.

In fact, many rheumatologists recognize that melatonin supplementation can increase the strength of the immune system in humans, and thus, they caution their autoimmune patients about using melatonin supplements, as it may exacerbate their autoimmune condition, such as rheumatoid arthritis or lupus.  As well, patients who have severe allergies, lymphoma or transplant patients on immunosuppressant drugs, are often cautioned by their doctor about taking melatonin supplements because of its potential to heighten immune system activity.

Reference No. 7

But for otherwise healthy adults, over the age of 40 (when melatonin levels are substantially lower), it may be wise to consider low dose melatonin supplementation one hour before bedtime, as an adjunctive strategy to support and strengthen immune function. Large, human intervention trials using melatonin for this purpose are still lacking, but preclinical studies are very impressive, showing positive effects on reversing many aspects of the aging process on the immune system. Remember that as you get older your body makes less and less melatonin and thus, higher and higher dosages may be required the older you get.

Here are some guidelines to consider if taking melatonin is something you wish to pursue:

  • From Age 40-50: 500 mcg – 1 mg (one hour before bedtime) – Melatonin
  • From Age 50-65: 1 – 2 mg (one hour before bedtime)- Melatonin
  • After Age 65: 1 – 3 mg (one hour before bedtime) – Melatonin

Note that if you wake groggy the next day the melatonin dosage you are taking is likely too high. So, start with a lower dosage and gradually increase it to find which dosage helps you get a good night’s sleep without zapping your energy the next day.

One final note is that studies suggest the consumption of too much refine sugar can also suppress immune function for many hours after its ingestion. This is one of the reasons that diabetics are immune-compromised. Higher blood sugar levels inhibit the ability of immune cells to secrete antimicrobial agents such as beta-defensins, which many immune cells use to burst a hole through the outer skin (membrane) of viruses trying to invade the respiratory tract and other body surfaces. So, keep your blood sugar in the ideal range, so your immune cells can generate this important anti-viral, anti-bacterial, anti-fungal agent, and also maintain their ability to trap and devour various threatening microbes.

References No 8, 9, 10.

I have included the references for all of this information in the text below.

I hope you found it to be helpful.


1. Laaksi I et al. Vitamin D supplementation for the prevention of acute respiratory tract infection: A randomized, double-blind trial among young Finnish Men. Journal of Infectious Diseases, Vol 202, Issue 5. September 2010.


2. Holick MF. Vitamin D: Importance in the prevention of cancers, type 1 diabetes, heart disease, and osteoporosis. Am J Clin Nutr. Vol 79, Issue 3. March 2004


3. Tapiovaara L, Pitkaranta A, Korpela R. Probiotic, and upper respiratory tract- A Review. Pediatric Infectious Diseases: Open Access. July 2016–a-review.php?aid=11295


4. Long JD and Morris. Probiotics in preventing acute upper respiratory tract infections. A. American Journal of Nursing. Dec 2017


5. Yan F and Polk DB. Probiotics and immune health. Curr Opin Gastroenterol. October 2011.


6. Yoo YM, Jang SK. Pharmacological advantages of melatonin in immunosenescence by improving the activity of T-lymphocytes. Journal of Biomedical Research. July 2016.




8. Kistler J, Wang X, Dubyak GR et al. Modification of beta-defensins-2 by dicarbonyls methylglyoxal and glyoxal inhibits antibacterial and chemotactic function in-vitro. PLOS One. August 2015.




10. Myles IA. Fast food fever: reviewing the impacts of the Western diet on immunity. Nutrition Journal. June 2014.


Other Notable References:


A. Wang Y et al. Probiotics for the prevention and treatment of respiratory tract infections in children: A systemic review and meta-analysis of randomized controlled trials. Systematic Review and Meta-Analysis. (Medicine) August 2016



B. C. Carrillo-Vico A et al. Melatonin: Buffering the immune system. Int. J. Mol, Sci, 14. April 2013.


Vitamin E:

D. Young Lee. G, Han SN. The role of vitamin E in immunity. Journal Nutrients. November 2018.


Eat Smart, Live Well, Look Great,

Dr. Meschino

Facebook Comments