Nutrients, by definition, are the food components that sustain your body's normal functions. They not only provide energy for vital metabolic reactions but also supply the building materials for normal structure, growth and repair. Your body needs relatively large quantities of carbohydrates, fats and protein for optimal function, hence their classification as macronutrients. They may contain similar constituent molecules but vary in their basic structure and energy yield.
Carbohydrates are the most abundant organic compounds in nature. Like fats, they're primarily made of carbon, oxygen and hydrogen molecules, with little to no nitrogen. These component molecules combine in different ways to form various saccharides, the basic unit of all carbs. You may encounter the words "saccharide" and "sugar" being used interchangeably. Monosaccharides are single-unit sugars and the simplest carbohydrate form. They can link up to form two-unit sugars, also known as disaccharides. Oligosaccharides contain three to 12 sugar units, while polysaccharides can be hundreds of sugar units long.
Fats belong to a broader family of compounds known as lipids. Their building blocks are fatty acids, a family of compounds with various arrangements of carbon, hydrogen and oxygen molecules. The combination of three fatty acids with the sugar alcohol glycerol forms triglycerides, the basic structural unit of all fats. The term "fat" usually refers to triglycerides that are solid or semisolid at room temperature, while oils contain liquid triglycerides at room temperature. Fats primarily occur in animal foods, although the triglycerides in fish are mostly oils, according to the Michigan State University Chemistry Department.
Saturated Vs. Unsaturated Fats
If you pay attention to nutrition labels on your food products, you've probably noticed the terms "saturated" and "unsaturated" fats. These terms simply refer to the spatial arrangement of the fatty acids in fats. In saturated fats, most of the fatty acids contain the greatest possible number of hydrogen atoms, with no double bond. This gives them a stacked appearance. In contrast, unsaturated fats have a majority of fatty acids that contain double bonds, giving them some fluidity. Monounsaturated fats contain fatty acids with primarily one double bond, while polyunsaturated fats have multiple double bonds.
Trans fats are somewhat special because even though they fall in the chemical classification of unsaturated fats, they behave more like saturated fats in your body. Indeed, like saturated fats, they tend to raise bad cholesterol levels in your blood and increase heart disease risk, says biochemist Pamela C. Champe. In contrast, unsaturated fats tend to be more heart-healthy. While small amounts naturally occur in animals, trans fats primarily come from chemical food processing.
Every living cell needs proteins. Beyond the structural role they play in your skin, hair, muscles, joints and other tissues, proteins act as hormones, help with molecule transport and accelerate metabolic reactions to keep you going. There are many naturally occurring amino acids, but 20 of them are the basic units of human proteins. Amino acids vary in their combination and spatial arrangement of carbon, hydrogen and nitrogen molecules. According to Michigan State University, proteins are made of 15 percent to 25 percent nitrogen and approximately the same proportion of oxygen.
- Lippincott's Illustrated Reviews: Biochemistry (3rd Edition); Pamela C. Champe, Ph.D. et al.
- Michigan State University: Carbohydrates
- Michigan State University: Protein
- Michigan State University: Lipids
- McKinley Health Center: Macronutrients: the Importance of Carbohydrate, Protein, and Fat