Our immune system is vital for a healthy life. It protects us from infectious agents that exist in the environment (bacteria, viruses, fungi, parasites) and from other noxious insults. The immune system is constantly active, acting to discriminate 'non-self' from 'self'.
Nutrient status is an important factor contributing to immune competence: undernutrition impairs the immune system, suppressing immune functions that are fundamental to host protection. Undernutrition leading to impairment of immune function can be due to insufficient intake of energy and macronutrients and/or due to deficiencies in specific micronutrients.
Nutrients that have been demonstrated to be required for the immune system to function efficiently include essential amino acids (protein), omega-3 essential fatty acid, vitamin E, and minerals. Practically all forms of immunity may be affected by deficiencies in one or more of these nutrients and adding the deficient nutrient back to the diet can restore immune function and resistance to infection.