The immune system has the job of defending the body against bacteria, viruses and anything else considered by the body to be foreign, or "non-self." Vitamins taken in the diet or as supplements are necessary components of a smooth and efficient-functioning immune system. Research has elucidated many of the specific roles that vitamins play on a daily basis to keep the immune system healthy.
Selenium
Selenium is a popular supplement used as an antioxidant and to boost immune function, according to the website NutritionalSupplementsCenter.com. According to a study published in the 2010 "Proceedings of the Nutrition Society," in order to determine the precise methods by which selenium influences the nervous system, researchers blocked the production of all proteins that selenium is connected to in mice and then observed the effects. The researchers noted a reduction in the numbers of T cells---a type of white blood cell---observing that the T cells were not fully mature or functional. Impairment in immune responses that rely on T cells was also noted, and cells with selenium deficiency were unable to control free radical production. Macrophages---another type of white blood cell---were not able to move toward a target pathogen as efficiently without selenium; however, they were otherwise able to carry out their functions normally.
Vitamin C
Vitamin C has been the subject of more studies regarding the immune system than any other vitamin, according to the website AskDrSears.com. This vitamin has the ability to increase white blood cell production and boosts interferon levels, preventing viruses from gaining a foothold, states the website. Vitamin C is also associated with decreased risk of colon, prostate and breast cancer. Since vitamin C is water soluble, it cannot be stored in the body and must be consumed on a daily basis. Additionally, it is best to obtain vitamin C, in the diet or as a supplement, in divided doses throughout the day to ensure optimal absorption.
Carotenoids
The carotenoids are a family of vitamin compounds, the most well-known of which is beta-carotene, long regarded as the water-soluble form of vitamin A. Beta-carotene increases numbers of natural killer cells and helper T cells, both members of the white blood cell group of immune cells, according to AskDrSears.com. Beta-carotene also prevents cancer by stimulating the production of tumor necrosis factor, which kills budding cancer cells. While beta-carotene is the most widely recognized of the vitamin A group, other carotenoids are important for their synergistic effect, which may not be obtained from taking beta-carotene or its fat-soluble form, vitamin A, in a supplement. A well-rounded diet that provides the full spectrum of carotenoids is generally the best way to obtain the full benefits.
