Summary
Highlights
Carbohydrates are composed of simple sugars (monosaccharides and disaccharides) and complex carbohydrates (oligosaccharides and polysaccharides). Simple sugars are ring-shaped molecules made of carbon, hydrogen, and oxygen, providing energy and playing various roles in food, such as sweetening and preservation.
Sugars are found naturally in plants and animal products like milk. Added sugars are those incorporated into foods, even if derived from natural sources such as sugarcane or honey. Many ingredients listed on food labels can be sources of added sugars.
Sugars are saccharides: monosaccharides (single sugar molecules like glucose, fructose, galactose), disaccharides (two molecules linked, like lactose, sucrose, maltose), oligosaccharides (3-9 molecules), and polysaccharides (10+ molecules). Glucose is a primary energy source for the body and brain.
Complex carbohydrates include oligosaccharides and polysaccharides. Starches are polysaccharides that human enzymes can break down for calories, found in foods like rice and potatoes. Dietary fibers are carbohydrates that the body cannot digest, offering health benefits like slowing sugar absorption and preventing constipation.
Monosaccharides link via glycosidic bonds. Different enzymes break down disaccharides, oligosaccharides, and polysaccharides into monosaccharides for absorption. Amylases break down starches, while lactase, sucrase, and maltase break down lactose, sucrose, and maltose, respectively.
Digested monosaccharides (glucose, fructose, galactose) enter the bloodstream. Insulin helps move glucose into cells and triggers the liver to store it as glycogen (glycogenesis). Galactose is converted to glucose in the liver, while fructose is mostly broken down for energy or converted into glucose.
The National Academies of Sciences recommend 45-65% of calories from carbohydrates. Fiber intake is suggested at 28 grams for a 2000-calorie diet. Both the WHO and US Dietary Guidelines recommend that added sugars make up less than 10% of total calories. Prioritizing nutrient-rich foods with fiber, starch, and natural sugars over those with added sugars.
Carbohydrates include simple sugars (monosaccharides, disaccharides), starches (polysaccharides), and fibers (partially digestible polysaccharides). A healthy diet includes a variety of carbohydrates from fruits, vegetables, dairy, and grains, with added sugars kept under 10% of total calories.