The immune system is a complex network of cells, tissues and organs that protects that body from microbes that cause disease. The organs of the immune system include the lymph nodes, bone marrow, spleen, thymus and tonsils. These organs produce cells and antibodies which fight infection. A person with a weak immune system may experience symptoms including fatigue, sore throat and swollen glands. According to the Hepatitis and AIDS Research Trust, emotional problems, illness and a poor diet can suppress immune function. Certain vitamins and minerals consumed as part of a healthy diet help to support immune function.
Vitamin A
Vitamin A can boost the immune system as well as counteract immune suppression by helping white cells fight off infection. Vitamin A is a fat-soluble vitamin found in foods such as liver, cheese, spinach, oatmeal and carrots. The National Institutes of Health Office of Dietary Supplements notes that animal-derived sources of vitamin A are more easily absorbed by the body than vitamin A found in fruits and vegetables. Vitamin A deficiency is rare in the United States, but symptoms include night blindness and greater susceptibility to infection.
Vitamin C
Vitamin C plays an important role in immune function by strengthening white blood cells and preventing bacteria from multiplying. Vitamin C is a water-soluble vitamin, which means the body is unable to store it. It must be obtained daily through the diet because the human body can't manufacture it itself. According to the Office of Dietary Supplements, fruit and vegetables are the best source of vitamin C. Fruits and vegetables particularly rich in vitamin C include tomatoes, green pepper, kiwi fruit and oranges. Vitamin C deficiency is rarely seen in the United States.
Zinc
Zinc is essential for a healthy immune system and for the treatment and prevention of respiratory infections, the common cold and ear infections. Zinc is an essential trace mineral. MedlinePlus notes that only a small amount is needed to maintain health. Good sources of zinc include milk and dairy products, wheatgerm, meat and shellfish. The U.K Food Standards Agency notes that the daily diet should provide the required amount of zinc.
Selenium
According to the results of a study published in the July 2004 issue of the "The American Journal of Clinical Nutrition," the mineral selenium may improve immune function. Lead author Caroline S. Broome notes that the patients who received a selenium supplement were able to clear a viral infection more quickly than those that received placebo treatment. The Office of Dietary Supplements notes that selenium is a trace element that is only required in small amounts. It is found in foods such as Brazil nuts, tuna, beef and eggs.
