Nutrition Science and Everyday Application - beta v 0.1

CLASSIFICATION OF NUTRIENTS 29
Figure 1.5. Macronutrients include proteins, carbohydrates, lipids, and water. This figure
illustrates each nutrient’s chemical structure and examples of food sources.
Carbohydrates
Carbohydrates are molecules composed of carbon, hydrogen, and oxygen. The major food
sources of carbohydrates are grains, dairy products, fruits, legumes, and starchy vegetables,
like potatoes. Non-starchy vegetables, like carrots, also contain carbohydrates, but in lesser
quantities.
Carbohydrates 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. 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.
Lipids
Lipids are also a family of molecules composed of carbon, hydrogen, and oxygen, but unlike
carbohydrates, they are insoluble in water. Lipids are found predominantly in butter, oils,
meats, dairy products, nuts and seeds, and in many processed foods. The three main
types of lipids are triglycerides, phospholipids, and sterols. The main job of lipids is to
provide or store energy. 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.