Nutrition is a science that studies the relationship between diet and health. Deficiencies, excesses and imbalances in diet can produce negative impacts on health, which may lead to diseases as well as psychological and behavioral problems. The science of nutrition attempts to understand how and why specific dietary aspects influence health.

The human body is made up of chemical compounds such as water, proteins, fats, nucleic acids such as DNA/RNA, and carbohydrates. These compounds in turn consist of elements such as carbon, hydrogen, oxygen, nitrogen, and minerals such as phosphorus, calcium, iron, or zinc. All of these chemical compounds and elements occur in various forms and combinations in the human body.

The human body through necessity includes these elements that it eats and absorbs into the bloodstream and feeds our cells that regulates our organs and the body's systems such as the nervous system, cardiovascular-circulatory system, endocrine system and gastrointestinal system. Our cells are the basic living units in our body and require carbohydrates, fats, and proteins to make energy for the body. The quality and amounts of these nutrients makes a vast difference in how efficiently our cells can make energy. So it makes sense to state that if our cells do not have the proper nutrients-compounds then our organs and body systems will not work at their optimal level.

It is important to consume these compounds/elements in the proper quantity and quality on a daily basis to build and maintain healthy bodily function. Poor health or imbalance of the body's systems can be caused by an imbalance of nutrients, either an excess or deficiency, which, in turn, affects bodily functions cumulatively. For example , because most nutrients are involved in cell-to-cell signalling, deficiency or excess of various nutrients affects hormonal function indirectly. Thus, because they largely regulate the expression of genes, hormones represent a link between nutrition and how our genes are expressed. The strength and nature of this link are continually under investigation, but recent observations have demonstrated a pivotal role for nutrition in hormonal activity and function and therefore in health.