What effects does diet have on the functioning on the human body?

Diet affects every system in the human body. Think about it. Every system, including bone, is in a constant state of rebuilding. Some materials, like calcium, can be recycled and used again in different parts of the body for short periods but generally the raw materials have to come in through the foods we eat. Any severe imbalance in the foods and nutrients consumed can cause many different types of illness, such as rickets, scurvy, etc. in a short period of time. This doesn't happen because we need these nutrients in stay in stasis, but because we need these nutrients to rebuild.