Vitamin D and Your Immune System
The 'sunshine vitamin' strengthens immune defenses and bone health, and why people with darker skin and certain conditions may need more.
Vitamin D is a fat-soluble nutrient that plays an essential role in immune function by affecting numerous cells that regulate the immune response. It specifically enhances the fighting, or defense, response of certain white blood cells, resulting in decreased inflammation. Without enough of it, the T cells of the immune system, or 'killer cells,' may not have the ability to attack serious infections or foreign pathogens in the body.
Vitamin D deficiency has been linked to susceptibility to infections such as respiratory infections, as seen with COVID-19 pneumonia. Numerous studies suggest that ensuring adequate vitamin D may help decrease the risk of respiratory infections. Vitamin D also promotes calcium absorption and bone health.
Vitamin D is produced and activated when the skin is exposed to sunlight (ultraviolet UVB light), and it can be found in foods such as sardines, fish liver oil, salmon, tuna, and fortified milk or orange juice, as well as in dietary supplements.
Some individuals need more. People with inflammatory bowel disease, celiac disease, malabsorption, obesity, or kidney disease, and minority populations, may need more supplementation when levels are very low. Individuals with darker skin have a higher risk of vitamin D deficiency because melanin (the pigment in skin) decreases the skin's ability to produce vitamin D from sun exposure.
For vitamin D intake recommendations, check in with your doctor. Additional guidance can be found from the Institute of Medicine and the National Osteoporosis Foundation.
Dr. Maggie Cadet, MD