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LMU 156 – Boosting Your Immune System: The Power of Vitamin D, Probiotics, and Melatonin


LMU 156 – Boosting Your Immune System: The Power of Vitamin D, Probiotics, and Melatonin

Source: Multiple Peer-Reviewed Journal Articles

Lifestyle Medicine Update (March 22, 2020)


Welcome back to the second part of our Nutrition and Immunity series. In part one, we delved into the common reasons behind a weakened immune system and explored the impact of specific vitamins, minerals, and herbal agents on immune function. In this second installment, we’ll continue our journey by focusing on three more nutrients that show great promise in supporting our immune system, particularly in the context of viral-induced respiratory tract infections.

Section 1: Vitamin D – A Sunshine Nutrient for Immunity

The Science Behind Vitamin D’s Immune-Boosting Abilities

One of the key players in our immune system’s defence against respiratory tract infections is Vitamin D. Research published in the Journal of Infectious Diseases in 2010 showcased how Vitamin D strengthens immunity. The study involved 164 young Finnish men undergoing military training, where those receiving 400 IU of Vitamin D per day had significantly fewer respiratory infections compared to those on a placebo.

The mechanism behind this lies in Vitamin D receptors found on immune cells lining the respiratory tract. These receptors allow Vitamin D to enter immune cells, where it’s converted into a potent form. In the cell nucleus, it modulates specific genes related to immunity, such as increasing the secretion of cathelicidin—a virus-killing molecule that punctures holes in viral and bacterial cell membranes, preventing infection.

To benefit from Vitamin D’s immune-boosting properties, maintaining blood levels above 80 nmol/L is crucial. If your levels are low, supplementation with 600-2,000 IU per day is often sufficient.

However, some individuals, like those with active tuberculosis or autoimmune conditions, should be cautious as their bodies may already produce excessive Vitamin D due to their condition.

Section 2: Probiotics – Your Gut’s Superheroes

Unleashing the Power of Probiotics

According to the World Health Organization, probiotics are live microorganisms that, when taken in adequate amounts, provide health benefits. These microorganisms, often friendly gut bacteria and yeast strains, play a significant role in enhancing both local and systemic immunity.

Probiotics work by improving the phagocytic capacity of immune cells, increasing specific immunoglobulin levels, and enhancing gut barrier functions. This means they help immune cells identify, engulf, and destroy pathogens, including respiratory viruses. Moreover, they boost immunoglobulin A, a crucial antibody protecting the respiratory and intestinal tracts from infections.

Studies have highlighted probiotics’ potential in alleviating allergies, eczema, viral infections, and enhancing vaccine responses. They modulate innate and adaptive immune responses, involving dendritic cells, macrophages, T and B lymphocytes, crucial players in immune defence.

In a recent Cochrane Review, probiotics proved more effective than placebos, reducing the incidence and duration of acute upper respiratory tract infections, with minimal side effects.

However, the ideal probiotic combination remains unknown. A mixture of lactobacillus, bifidobacterium, streptococcus, and Saccharomyces cerevisiae strains can provide substantial benefits.

To harness probiotics’ power, consider supplements delivering 2-10 billion living microorganisms per day.

Section 3: Melatonin – Your Sleep Hormone and Immune Supporter

The Sleep Hormone’s Immune Benefits

Melatonin, primarily known for regulating sleep-wake cycles, also has an important role in immune function. As we age, melatonin production decreases, contributing to immunosenescence, the weakening of the immune system with age.

CD4 cells, the quarterbacks of the immune system, have melatonin receptors. Reduced melatonin levels in aging result in weaker CD4 cell modulation, leading to a less efficient immune system. Experimental studies suggest that supplementing melatonin can rejuvenate various immune parameters in aging individuals.

While melatonin can strengthen the immune system, it may exacerbate autoimmune conditions, severe allergies, or affect transplant patients on immunosuppressant drugs.

For healthy adults over 40, low-dose melatonin supplementation one hour before bedtime can be considered to support immune function. Dosages may vary from 500 mcg to 3 mg, depending on age and individual response.

Section 4: Dietary Impact on Immunity

The Role of Diet in Immunity

Lastly, it’s essential to consider the impact of diet on immunity. Excessive consumption of refined sugar can suppress immune function for hours after ingestion. This is especially concerning for diabetics, as high blood sugar inhibits the ability of immune cells to fight off infections effectively.

Maintaining ideal blood sugar levels ensures that immune cells can produce antimicrobial agents like beta-defensins, vital for warding off viruses and other pathogens.


In this second part of our Nutrition and Immunity series, we’ve explored the powerful immune-boosting potential of Vitamin D, probiotics, and melatonin. Maintaining optimal levels of these nutrients, along with a balanced diet, can significantly enhance your immune system’s ability to defend against respiratory tract infections and other health threats. While more research is needed, these strategies offer promising avenues for bolstering your overall health and well-being.


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  3. [Link to reference on Probiotics](–a-review.php?aid=11295)
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  7. [Link to reference on Melatonin](
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Eat Smart, Live Well, Look Great,

Dr. Meschino

Dr. James Meschino


Dr. James Meschino, DC, MS, ROHP, is an educator, author, and researcher having lectured to thousands of healthcare professionals across North America. He holds a Master’s Degree in Science with specialties in human nutrition and biology and is recognized as an expert in the field of nutrition, anti-aging, fitness, and wellness as well as the author of numerous books.

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