Six Major Classes of Nutrients

There ar six major classes of nutrientscarbohydrates,fats,minerals,protein,vitamins, andwater. These nutrient classes can be categorized as allmacronutrients(needed in relatively large amounts) ormicronutrients(needed in smaller quantities). The macronutrients include carbohydrates (includingfiber), fats, protein, and water. The micronutrients are minerals and vitamins. The macronutrients (excluding fiber and water) provide structural material ( amino acids from which proteins are built, and lipids from which cell membranes and some(prenominal) signaling molecules are built) and nix.Some of the structural material can be used to generate readiness internally, and in either case it is measured inJoulesorkilocalories(often called Calories and written with a capitalCto distinguish them from little c calories). Carbohydrates and proteins provide 17kJ approximately (4kcal) of energy per gram, while fats provide 37kJ (9kcal) per gram. ,17though the net energy from either depends on suc h factors as absorption and digestive effort, which vary substantially from instance to instance.Vitamins, minerals, fiber, and water do not provide energy, but are required for other reasons. A third class of dietary material, fiber (i. e. , non-digestible material such as cellulose), is also required,citation neededfor both mechanical and biochemical reasons, although the shoot reasons remain unclear. Molecules of carbohydrates and fats consist of carbon, hydrogen, and oxygen atoms. Carbohydrates range from simplemonosaccharides(glucose, fructose, galactose) to complexpolysaccharides(starch).Fats aretriglycerides, made of assorted superfatted acidmonomersbound to aglycerolbackbone. Some fatty acids, but not all, areessentialin the diet they cannot be synthesized in the body. Protein molecules contain nitrogen atoms in addition to carbon, oxygen, and hydrogen. The fundamental components of protein are nitrogen-containingamino acids, some of which areessentialin the sense that huma ns cannot make them internally.Some of the amino acids are convertible (with the expenditure of energy) to glucose and can be used for energy production, just as ordinary glucose, in a process known as gluconeogenesis. By breaking down existing protein, some glucose can be produced internally the remaining amino acids are discarded, primarily as urea in urine. This occurs normally only during prolonged starvation. Other micronutrients includeantioxidantsandphytochemicals, which are tell to influence (or protect) some body systems.Their necessity is not as well established as in the case of, for instance, vitamins. Most foods contain a swagger of some or all of the nutrient classes, together with other substances, such as toxins of various sorts. Some nutrients can be stored internally (e. g. , the fat water-soluble vitamins), while others are required more or less continuously. Poor health can be caused by a lack of required nutrients or, in extreme cases, too much of a required nutrient. For example, both salt and water (both absolutely required) will cause illness or even expiration in excessive amounts.