Sometimes the human body fails to process food as it should and physical problems develop that are actually caused by the food. Sometimes eating a diet that isn’t balanced, is too rich, or contains too much of certain substances can also cause physical difficulties to develop.

The immune system of a human body can misidentify a perfectly harmless food as a foreign invading force bent on destroying the body. The immune system mounts a defense to protect the body from this perceived danger. The food isn’t a danger to the body, but the defense staged by the body to combat it is dangerous. When this happens, we call it an “allergic reaction.”

Some people can have such severe allergies to certain foods (peanuts, for example) that even a very small amount can cause an allergic reaction that is so strong that death can occur.

In other instances, the body doesn’t process food correctly. An example of this is sugar diabetes. The pancreas fails to produce any insulin (needed to process carbohydrates) or it doesn’t produce enough. When no insulin is produced, the problem is called Type 1 diabetes and is usually diagnosed in childhood or early adulthood. When the pancreas fails to produce enough insulin, it’s called Type 2 diabetes and is usually diagnosed in people over 40.

Doctors prescribe diets for special needs for many reasons. The body failing to digest food correctly and allergic reactions to food are two reasons. But there are others, as well.