Carbohidrats

Carbohidrats are a broad class of organic compounds composed of carbon, hydrogen, and oxygen, typically with the empirical formula (CH2O)n. They function mainly as energy sources and storage molecules in living organisms, and they also provide structural materials in plants and some invertebrates. In nutrition, carbohydrates are often categorized by their structure and the speed with which they affect blood glucose.

Carbohidrats include monosaccharides (simple sugars such as glucose, fructose, galactose), disaccharides (sucrose, lactose, maltose), and polysaccharides (starch, glycogen, cellulose). Oligosaccharides contain a small number of monosaccharide units. Starch is the main energy reserve in plants; glycogen serves a similar role in animals; cellulose provides structural support in plant cell walls; chitin is a structural polymer in arthropods and fungi.

Digestive enzymes break down these compounds in the digestive tract: amylases act on starch; disaccharidases such as sucrase, lactase, and maltase break disaccharides into monosaccharides. Monosaccharides are absorbed in the small intestine, mainly glucose, galactose, and fructose, via transporters such as SGLT1 and GLUT2 (for glucose and galactose) and GLUT5 (for fructose). They enter the liver through the portal vein and participate in glycolysis, glycogenesis, or lipogenesis as needed.

Dietary carbohydrates come from fruits, vegetables, grains, and legumes. Dietary fiber, consisting of soluble and insoluble non-digestible carbohydrates, is not absorbed but supports gut health and may lower certain disease risks. High intake of refined sugars and low-fiber carbohydrates is associated with adverse metabolic outcomes, whereas a balanced carbohydrate intake from diverse, minimally processed sources is generally recommended.