Health Benefits of Vitamin D on Our Immune System

Dr. Mikael Brucker, ND, LAc at Yang Institute of Integrative Medicine

Vitamin D may be thought of more as a hormone than a nutrient due to the many chemical variations in which it is found in the body, and its broad effects. Although Vitamin D was originally studied mostly for its effect on skeletal health, it is also known to be involved in muscle movement, nerve transmission, and immune reaction to virus and bacteria. It has a forming action, instilling structural integrity in all body systems.

Research has shown deficiency to be associated with: dental caries, peritonitis, autoimmune disorders, infectious disease, cardiovascular disease, cancer, type 2 diabetes, and neurological disorders1. Its broad and deep effects on the body can be attributed to its ability to alter gene expression in our cell’s nucleus2. Vitamin D, therefore,  has epigenetic effects.

Effect on immunity

Vitamin D affects immunity to infectious disease in three broad areas: physical barrier function, innate immunity, and adaptive immunity. It maintains structural integrity for the cell to cell binding in barrier tissue such as the respiratory and digestive tract preventing pathogens from entering the body. It promotes the expression of cathelicidins known to reduce pro-inflammatory cytokines that can damage respiratory cells while increasing anti-inflammatory cytokines. It also increases defensins which have been shown to lower viral replication rate.  Finally, it affects adaptive immunity by increasing T regulating cells which help balance the expression of TH1 and TH2 pathways2.

Vit D has been proposed by former CDC director Dr. Tom Frieden, MD as a possible treatment to combat the COVID 19 pandemic. There is some clinical data showing direct evidence of Vit D for treating COVID 19 patients. COVID 19 patients treated in one Georgia hospital with high dose Vit D (500,000 IU) cut hospital stays in half from 36 to 18 days compared to control2. Other studies have shown that Vit D deficiency contributes to acute respiratory distress syndrome (ARDS). Broadly, Vit D has shown in a systematic review of 11,000 participants to reduce the risk of upper respiratory infection3. There is a hypothesis that Vit D levels contribute to the seasonal effect of influenza rates, an effect that is not seen in populations closer to the equator2.

Food & Natural Sources 

Food wise, Vitamin D is found primarily in fatty fish including tuna, herring, salmon and mackerel4. Most people get their Vitamin D from artificially fortified dairy and grain products. One can also get Vitamin D from sunlight. Exposure of half the body to 50% of the intensity that would cause mild sunburn is equivalent to 5000 IUs of Vitamin D1.

At Risk Groups

It is estimated that 30% of the world is Vitamin D deficient (<20ng/ml) and 60% is insufficient (20-30ng/ml).  30ng / mL is the level at which parathyroid hormone levels stabilize in the blood indicating balanced osteoclast and osteoblast activity1. Factors that increase the risk for deficiency include obesity, certain pharmaceutical (prednisone, cholestyramine, Dilantin), lack of sunlight, digestive disorders, and older age.

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