The immune system is made up of cells, tissues, organs, and processes that identify a substance as abnormal or foreign and prevent it from harming the body. Primary defenses include the white blood cells , but skin, mucosa , normal bacteria , enzymes , and proteins also provide protection. During times of stress and malnutrition , immune function may be decreased, meaning that susceptibility to illness is increased. Proper nutrition , including adequate protein, calories , and antioxidants (such as vitamin C, vitamin E, and beta-carotene, which are all found in fruits and vegetables) may help to improve immune response and reduce the risk of illness.
SEE ALSO Infection .
Shils, Maurice, et al. (1999). Modern Nutrition in Health and Disease, 9th edition. Baltimore, MD: Williams & Wilkins.