A 'nutrient' (NOO-tree-unt) is a substance you get from food. It's used by the body for growth, maintenance, or repair of tissues. There are six categories of nutrients: proteins, carbohydrates, fats and oils, vitamins, minerals, and water. Water is the most abundant nutrient in the body, a component of every cell, and accounts for 60 percent of body weight. 'Essential' nutrients are substances the body is unable to make on its ownand must be obtained from food. These include up to 10 amino acids, most of the 13 vitamins, some 20 minerals, and an oil called linoleic (lin-oh-LAY-ic) acid. The term 'essential' means that the body is dependent on diet as a source of the nutrient. Intake levels for essential nutrients are suggested through the Recommended Dietary Allowances, or 'R-D-A's.