The immune system is the first line of defense against infections to the body. Infections are caused by bacteria, parasites and viruses. They range from causing a common cold to more debilitating diseases. It is important to keep the immune system strong to fight disease and infection. The National Institutes of Health states that even a mild deficiency in certain vitamins and minerals can cause an altered immune response.
Vitamin A
Vitamin A is an important component of the body's defense system and for fighting infection. It provides support to the immune system by maintaining adequate levels of circulating immune cells, specifically the T cells, often referred to as the fighter cells. Vitamin A also increases the activity of white blood cells, which attack and destroy infected cells of the body. It is present in two forms found in foods: retinoids or preformed vitamin A, and carotenoids. Preformed vitamin A is found only in animal food sources such as liver, eggs and milk. Good food sources of carotenoids (which are converted to vitamin A in our body) are sweet potatoes, carrots, spinach, collard greens, kale, butternut squash and cantaloupe. The daily recommended intake, or DRI, set by the U.S. Department of Agriculture for vitamin A is 700 micrograms, or mcg, per day for adult females. For adult males, the daily recommended intake is 900 mcg per day.
Vitamin C
Vitamin C, also known as ascorbic acid, is essential for the formation of adrenal hormones and the production of lymphocytes. Adrenal hormones are important for protection against infection. Decreases in adrenal hormone levels can lead to an increase response to infections. Lymphocytes, which consist of both T cells and B cells, directly protect the body against infections. An adequate level of vitamin C insures that lymphocyte production is at its peak. Cherries, red bell peppers, strawberries, oranges, cantaloupe, broccoli and rosehips all supply a healthy dose of vitamin C. Many packaged foods are fortified with vitamin C. Examples include breakfast cereals, energy bars and fruit juices. The DRI for vitamin C is 65 mg per day for females 14 to 18 years old and 75 mg per day for females over age 19. For males, the DRI is 75 mg per day for ages 14 to 18 and 90 mg per day for males over age 18.
Vitamin E
Acting as a scavenger of toxic free radicals that damage otherwise healthy cells, vitamin E is one of the body's primary antioxidants. Antioxidants serve to protect healthy cells in the body. Vitamin E's activity is an integral part of the body's defense system as it serves to enhance antibody activity, specifically T cell function of fighting infectious agents. Vegetable oils, such as olive and canola, are rich sources of vitamin E, as are almonds, avocados and wheat germ. The DRI for vitamin E is 15 mg per day for adult males and females.
B Vitamins
While there are eight B vitamins in all, B6 and B12 specifically impact the immune system. Since vitamin B6 is important for fat and protein metabolism, a deficiency causes altered metabolic processes. Low levels of vitamin B6 leads to a reduced activity of white blood cells necessary for fighting infections in the body. A vitamin B6 deficiency can also lead to a shrinkage of the thymus, a critical immune system organ. The DRI for adult males 18 to 50 years old is 1.3 mg and 1.7 mg for males over 50 years old. For adult females, the DRI is 1.3 mg for ages 18 to 50. For females over 50 years old, the DRI is 1.5 mg. Vitamin B12 plays an important role in cell division and growth. It is responsible for the ability of white blood cells to destroy infecting organisms. The DRI for B12 is 2.4 mcg for adult males and females. Rich sources of the B vitamins are whole grains such as wheat and oats, fish, poultry and eggs.
