Without it, nothing could be transported in or out of the body, chemical reactions would not occur, organs would not be cushioned, and body temperature would fluctuate widely. More than 60 percent of your total body weight is water. Water does not contain carbon but is composed of two hydrogens and one oxygen per molecule of water.
There is one other nutrient that we must have in large quantities: water. Proteins can also provide energy, though this is a relatively minor function, as carbohydrates and fat are preferred energy sources. Scientists estimate that more than 100,000 different proteins exist within the human body. Proteins provide structure to bones, muscles, and skin, and they play a role in conducting most of the chemical reactions occurring in the body. The word protein comes from a Greek word meaning “of primary importance,” which is an apt description of these macronutrients as they are also known as the “workhorses” of life. Food sources of proteins include meats, dairy products, seafood, and a variety of plant-based foods, like beans, nuts, and seeds. Proteins are large molecules composed of chains of amino acids, which are simple subunits made of carbon, oxygen, hydrogen, and nitrogen. In addition to energy storage, lipids serve as major components of cell membranes, surround and protect organs, provide insulation to aid in temperature regulation, and regulate many other functions in the body. The main job of lipids is to provide or store energy. The three main types of lipids are triglycerides, phospholipids, and sterols. Lipids are found predominantly in butter, oils, meats, dairy products, nuts and seeds, and in many processed foods. Lipids are also a family of molecules composed of carbon, hydrogen, and oxygen, but unlike carbohydrates, they are insoluble in water. Carbohydrates are a major fuel source for all cells of the body, and certain cells, like cells of the central nervous system and red blood cells, rely solely on carbohydrates for energy.
Non-starchy vegetables, like carrots, also contain carbohydrates, but in lesser quantities.Ĭarbohydrates are broadly classified into two groups based on their chemical structure: simple carbohydrates (often called simple sugars) and complex carbohydrates, which include fiber, starch, and glycogen. The major food sources of carbohydrates are grains, dairy products, fruits, legumes, and starchy vegetables, like potatoes. CarbohydratesĬarbohydrates are molecules composed of carbon, hydrogen, and oxygen. This figure illustrates each nutrient’s chemical structure and examples of food sources. Macronutrients include proteins, carbohydrates, lipids, and water. Water is also a macronutrient in the sense that you require a large amount of it, but unlike the other macronutrients, it does not yield that you require a large amount of it, but unlike the other macronutįigure 1.5. There are three classes of macronutrients: carbohydrates, lipids, and proteins. Nutrients that are needed in large amounts are called macronutrients. We’ll discuss these different ways of classifying nutrients in the following sections. Nutrients can be further classified as either macronutrients or micronutrients and either organic or inorganic, as well as whether or not they provide energy to the body ( energy-yielding). Nutrients are chemical substances found in food that are required by the body to provide energy, give the body structure, and help regulate chemical processes. This section will discuss the six classes of nutrients and how these nutrients can be classified.
Food also provides our body with essential nutrients and non-nutrients like phytochemicals, both of which are vital to health. It offers amazing flavors, aromas, and textures. Food is one of life’s greatest pleasures.
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