Nutrition is the nourishment of an organism to support its functions, with substances called nutrients. In humans, nutrition more specifically refers to the consumption, absorption, utilization and excretion of essential chemical compounds found in foods and drinks that are required by the body to produce energy as well as to assist the body to grow and develop. Nutrients also help the body prevent or fight diseases more effectively. There are six major classes of nutrients which include carbohydrates, fats, proteins, vitamins, minerals and water. Other substances have been identified that play an important role in human health such as phytochemicals, but are not yet considered being essential. Nutrients cannot be created by the body and thus must be obtained through diet. Diet, in turn, refers to the total consumption of food by an organism and is sometimes used interchangeably with nutrition, although the two terms have different meanings.
Nutritional science is the study of nutrients, their function and how they are involved in health and disease. The goal is to ensure specific nutritional guidelines suitable for different groups of people depending on their age, sex, activity level and special groups such as in pregnancy or disease. It is a relatively new discipline and began to evolve the last 100 years, even though the importance of diet to maintain health was recognised a lot earlier. It is an applied subject that draws information from many other biological areas particularly biochemistry, therefore a good understanding of biochemistry is required to fully understand nutrition. Nutritional scientists employ many of the techniques used in biochemistry, although nutritionists are more health oriented and concerned particularly with nutrients. In fact, the wealth of knowledge of nutrition is greatly attributed to biochemists.
In the following chapters we discuss the biochemistry of nutrients and how they are metabolised in the body.