How does diet affect the immune system?

The immune system is a system of biological structures and processes within an organism that protects against disease

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 Here are some facts from two articles I researched.

"Adding fruits and vegetables and other nutrient sources may help keep you from getting sick" (Tufts University Health & Nutrition Letter).

In the article Tufts University Health & Nutrition Letter, it explains how they found a new study where older adults who increased their fruit and vegetable consumption to at least five servings a day showed a significantly greater response to a pneumonia vaccine than those in a control group. Consumption of specific nutrients, such as vitamin E, carotenoids and vitamin C has been associated with improved immune function as well. In another study, they showed how adults who improved their micronutrient status through their diet or by consuming a low-dose multivitamin reported fewer visits to the doctor or hospital over a six-month span!

"Foods that Fuel the Immune System" (Newsletter of food, nutrition & health)

"When your immune system is healthy you have multiple barriers to protect against invaders, including skin, inflammatory responses, and specific immune responses, such as certain types of white blood cells that destroy pathogens." In this article I found out that Vitamin E supplementation helps reduce the risk of upper respiratory infections, such as the common cold. Some foods packed with vitamin E are nuts, olives and leafy greens. Also, while most people believe decreasing calories on their diet will help them lose weight, they also need to think about their immune system. You must eat enough, but not too much. If you decrease calories too much it will result in nutritional deficiencies which is not good for the immune system.