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Vitamin D and Immune Support

With the current fears surrounding the Coronavirus, I figured it would be a good time to share some knowledge about ways that can we can boost our immune system and take care of ourselves while we are social distancing. The next series of blogs and social media posts will be focusing on our immune system and mental health. I want to start by saying the content featured here will be general evidence-based information regarding your immune system. There is very little scientific literature on the COVID-19 virus itself. Any advice given in these posts will be for longevity and general information about boosting your natural ability to fight infections. Always check with your primary health care provider before making any changes to your regular routines.

Now that the technical jargon is out of the way - let’s talk about the most overlooked nutrient in regards to your immune system.

The winter season is notorious for colds and flu. Every year, starting at the beginning of fall, stores stock up on their cold and flu products, and the advertising for the flu shot begins. It is like clockwork. We expect to get sick this time of year. There are many theories as to why people get sick more in the winter than any other season. Is it the cold weather? Is it because we are all forced inside closer together? What is it about the winter months that spike the rate of illness? My theory, amongst many others, is that we all experience a decline in vitamin D during the winter, which impacts the function of our immune system, both innate and adaptive (Prietl et al., 2013). Vitamin D influences many systems within the body. Unfortunately, about one billion people today are deficient in this vitamin and deficiency most prevalent in the elderly community older than 65 years old.

““Whoever wishes to investigate medicine properly should proceed thus: in the first place to consider the seasons of the year…” (Hippocrates, ca. 400 BC)”

-(Gruber-Bzura, 2018).

Despite the name, leading experts and health officials are categorizing vitamin D as a hormone instead of the vitamin. Vitamin D is primarily associated with skeletal health and calcium absorption. Still, research is finding that it can play a critical role in the development of many significant health conditions like diabetes, autoimmune disorders like multiple sclerosis, and gastrointestinal disorders (Cesari et al., 2011). Our body synthesizes vitamin D after being exposed to ultraviolet B radiation from the sun. Researchers say that 5-10 minutes of arm and leg exposure during mid-day summer sun can provide up to 3000 IU of vitamin D to a person (Cesari et al., 2011). It is uncommon for food to have sufficient levels of vitamin D naturally. Fortified foods like milk and cheese contain added vitamin D, while salmon, sardines, and shitake mushrooms naturally have trace amounts. Because of the low quantities of vitamin D in food, it is rare to achieve 800 IU daily with diet alone. In the winter months, especially in the northern hemispheres, our exposure to UVB rays is limited, and our vitamin D levels decline naturally. The decline of vitamin D in the elderly may be specific to their inability to store it

Vitamin D receptors (VDR) are found in many tissues throughout the body. The vitamin D interactions with VDR can modulate the innate immune response, giving it a protective role. The innate immune response is the first line of defense against pathogens in the body. Once a toll-like receptor recognizes a pathogen (i.e., virus, bacteria), a cascade response signals the release of first responders antimicrobial peptides, such as macrophages, monocytes, cytokines, neutrophils and epithelial cells that line the respiratory tract. Antimicrobial peptides (AMP) are highly dependent on vitamin D. Defensins and cathelicidin, two AMPs stimulated by vitamin D, plays a critical role in fighting influenza. (Gruber-Bzura, 2018). AMPs protect epithelial tissues (think lungs) by destroying lipoproteins from pathogens preventing the attachment of them to the epithelial lining (Mawson, Chan, Kawai, & Lai, 2013). It is because of the association Vitamin D has with the epithelial cells of the lungs that lead many to believe that vitamin D deficiency increases the risk for respiratory illnesses (Larkin & Lassetter, 2014).

Vitamin D is also able to reduce the pro-inflammatory cytokines that are released by viruses and pathogens. One study found that Vitamin D treatment before and post H1N1 exposure decreased infection-induced cytokines. By reducing the impact of the pathogen, the immune system is better able to take over and protect the body. Experts believe that the increase of influenza in the wintertime is due to a decrease in the production of AMPs as a side effect of vitamin D deficiency (Mawson, Chan, Kawai, & Lai, 2013).

The biggest take away: Vitamin D both modulates the immune system and anti-inflammatory. It is protective of the body and necessary for your innate immune system (first line of defense). Have your vitamin D levels checked.

There is controversy over what levels of vitamin D are considered deficient. Serum 25(OH)D is the most accurate biomarker for vitamin D status. The Endocrine Society suggests that levels below 20 ng/mL (50 nmol/L) defines a deficiency (Prietl et al., 2013). The optimal range for health and longevity should be 30 ng/mL (75 nmol/L) or higher, with a preference around 40-70 ng/mL. Because we are not spending adequate time in the sun with skin exposure, supplementation to maintain healthy vitamin D status is often necessary. There are two types of vitamin D usually found in supplements: vitamin D2, plant-derived, and D3, animal-derived (Balvers et al., 2015). Animal-derived D3 is more absorbable of the two forms.

The International Osteoporosis Foundation recommends a dietary intake of 800-1000 IU of vitamin D a day for seniors over the age of 60 (Guilliams, 2017). When trying to optimize serum vitamin D levels, increased supplementation is often necessary. One report cited by Guilliams (2017) suggests that taking 1000 IU vitamin D daily can increase serum levels by 10 ng/mL over 3-4 months. By these findings, increasing to 2000 IU daily for a generally healthy person would be necessary to achieve a 30 ng/mL increase within the same period. Some doctors may even prescribe high doses of vitamin D depending on the deficiency status. Supplementation of vitamin D may vary by person and need, which is why it is always important to check with a primary health care physician before implementing changes.

There needs to be more research on the potential role of vitamin D deficiency and the increased risk of infections in the winter months. Although, the research provided within this article does support the hypothesis considering the active role vitamin D plays in the immune system. The elderly are more susceptible to illnesses, and the rates of infection increase in the winter, especially respiratory infections (Gunville, Mourani, & Ginde, 2013). Vitamin D deficiency affects billions of people globally, especially the older population over the age of 65. During this time, we need to pay close attention to how we can increase our first line of defense against pathogens, which may depend on sufficient vitamin D status.



Balvers, M. G., Brouwer-Brolsma, E. M., Endenburg, S., de Groot, L. C., Kok, F. J., & Gunnewiek, J. K. (2015). Recommended intakes of vitamin D to optimise health, associated circulating 25-hydroxyvitamin D concentrations, and dosing regimens to treat deficiency: workshop report and overview of current literature. Journal of nutritional science, 4, e23.

Cesari, M., Incalzi, R. A., Zamboni, V., & Pahor, M. (2011). Vitamin D hormone: a multitude of actions potentially influencing the physical function decline in older persons. Geriatrics & gerontology international, 11(2), 133–142.

Gruber-Bzura B. M. (2018). Vitamin D and Influenza-Prevention or Therapy?. International journal of molecular sciences, 19(8), 2419.

Gulliams, T.G. (2017). Supplementing Dietary Nutrients. Stevens Point, WI: Point Institute.

Gunville, C. F., Mourani, P. M., & Ginde, A. A. (2013). The role of vitamin D in prevention and treatment of infection. Inflammation & allergy drug targets, 12(4), 239–245.

Prietl, B., Treiber, G., Pieber, T. R., & Amrein, K. (2013). Vitamin D and immune function. Nutrients, 5(7), 2502–2521.

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