The immune system has the job of defending the body against bacteria, viruses and anything else the body considers foreign, or "non-self." Vitamins are necessary components of an efficient and effective 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 an important antioxidant and immune-boosting nutrient, according to the website NutritionalSupplementsCenter.com. To determine the precise methods by which selenium influences the nervous system, a study published in the 2010 "Proceedings of the Nutrition Society" 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 the white blood cells known as T-cells, observing that the T-cells were not fully mature or functional. Researchers also noted an impairment in immune responses that rely on T-cells, and cells with selenium deficiency were unable to control free radical production. Fish such as cod, tuna, snapper and halibut top the list for selenium content, according to the World's Healthiest Foods. Oats, barley and sunflower seeds are good plant sources.
Vitamin C
Vitamin C has been the subject of more studies regarding the immune system than any other vitamin, according to AskDrSears.com. This vitamin has the ability to increase white blood cell production and boost interferon levels, preventing viruses from gaining a foothold, says the website. Vitamin C is also associated with decreased risk of colon, prostate and breast cancer. Since vitamin C is water-soluble, the body cannot store it, so you must consume it on a daily basis. Additionally, it is best to obtain vitamin C in divided doses throughout the day to ensure optimal absorption.
Carotenoids
The carotenoids are a family of water-soluble vitamin compounds found in high concentrations in orange-, yellow- and red- colored plants, the most well-known of which is beta-carotene. Beta-carotene increases numbers of natural killer cells and helper T-cells, both of which are members of the white blood cell group of immune cells, according to AskDrSears.com. Beta-carotene also prevents cancer by stimulating the production of a molecule known as tumor necrosis factor, which kills developing cancer cells. While beta carotene has been the most researched of the carotenoid group, other carotenoids are important for their synergistic effect, which may not be obtained from taking beta carotene as a supplement, according to Answers.com. A well-rounded diet that provides the full spectrum of carotenoids--especially carrots, sweet potatoes, winter squash, kale, spinach and collard greens, says the World's Healthiest Foods--is generally the best way to obtain the full benefits.
