Every stage of a healthy immune system relies on specific vitamins, including vitamins D, E, and C. The immune system is a complex array of physical and biochemical barriers, specialized immune cells, and antibodies to target potential pathogens. It is suggested that individuals with inadequate dietary intake or undergoing infection, stress, or toxin exposure may require more immune-supportive vitamins than the recommended dietary intake, as even marginal deficiencies may negatively impact immune function. 

Vitamin C is a well-known immune-supportive vitamin. Not only does vitamin C promote innate and adaptive immune functions, but it also serves as a potent antioxidant. Vitamin C regenerates other critical antioxidants to their active state, including glutathione and vitamin E. It promotes white blood cell proliferation, function, and movement. Among many roles, it can support antimicrobial properties, increase serum complement proteins, attenuate histamine levels, and modulate proper cytokine production. Human studies in adults, children, and athletes observe that vitamin C supplementation may help support a healthy immune system and promote a healthy microbial environment.  

Vitamin D is integral for innate physical barriers to immune health. It supports a healthy gut barrier by increasing tight junction protein expression and promotes a healthy gut microbial environment. Approximately 70% to 80% of the immune system is in the gut. Vitamin D promotes lung, kidney, and eye epithelial barrier function when exposed to potential pathogens. It is also involved in reducing the expression of pro-inflammatory cytokines and increasing the expression of anti-inflammatory cytokines. It plays an integral role in the proper differentiation and function of monocytes to macrophages.  

Five meta-analyses concluded that vitamin D supplementation between 300 IU per day to 3,653 IU per day in adults and children promotes respiratory tract health. Low vitamin D levels have been observed in higher disease activity and severity in autoimmune diseases such as rheumatoid arthritis, lupus, and multiple sclerosis.  

Vitamin E is a fat-soluble antioxidant that protects cell membranes from damage caused by free radicals and supports the integrity of epithelial barriers. Vitamin E indirectly promotes T-cell function by decreasing prostaglandin E2 from macrophages and is necessary to maintain the Th1/Th2 balance. 

In vitro, tocotrienols (a vitamin E subtype) enhanced lymphocyte proliferation and facilitated immune responses to antigens. Studies suggest the beneficial immunomodulatory effect of tocotrienols may be more pronounced in aging individuals, as seen in a double-blind controlled trial of subjects receiving 400 mg of tocotrienols per day, but further research is needed. 

There is an overlap in the immunomodulatory roles of vitamins D, E, and C. For example, all three vitamins support the differentiation, proliferation, and normal functioning of T cells. Proper intake of each vitamin through diet or supplementation is required for their unique roles in supporting the immune system.

By Danielle Moyer, MS, CNS, LDN