Carbohydrates are the body's main source of energy, and the brain relies on the glucose they provide. They are found in grains, fruit, vegetables, beans, milk and sugary foods, in three main forms: sugars, starches and fiber. Which kinds you eat matters at least as much as how much.
Sugars, starches and fiber
Sugars are the simplest carbohydrates. Some occur naturally, like the fructose in fruit and the lactose in milk. Others are added to foods and drinks during processing or at the table, including table sugar, honey, syrups and fruit juice concentrates.
Starches are long chains of sugar units, found in grains, potatoes, corn, beans and other starchy vegetables. The body breaks them down into glucose.
Fiber is the part of plant foods the body can't digest. It helps digestion, keeps you full and feeds the bacteria in your gut, and fiber-rich diets are linked to a lower risk of heart disease and type 2 diabetes. See fiber facts.
Whole grains and refined grains
A whole grain keeps all three parts of the kernel: the fiber-rich bran, the nutrient-rich germ and the starchy endosperm. Refining removes the bran and germ, and with them much of the fiber, vitamins and minerals. Whole wheat, oats, brown rice, barley, rye, quinoa and corn are good choices; white bread, white rice and many crackers and cereals are refined.
The 2025–2030 Dietary Guidelines for Americans recommend two to four servings of whole grains a day and a significant cut in refined carbohydrates. See pasta and a healthy diet for how pasta fits in.
Added sugars
Added sugars supply calories with few other nutrients, and many people eat far more than they need, much of it in sweetened drinks. US guidance has tightened. The 2025–2030 Dietary Guidelines say no amount of added sugar is recommended, suggest no more than 10 grams in any one meal, and advise that children avoid added sugars until about age 10. The previous guidelines set a limit of 10% of daily calories, about 50 grams on a 2,000-calorie day.
The "added sugars" line on US nutrition labels is the easiest way to see how much a food contains.
Fast and slow carbohydrates
Different carbohydrate foods raise blood sugar at different speeds. The glycemic index ranks them against pure glucose: beans, lentils, oats and most fruits are low, while white bread and many breakfast cereals are high. Fiber, protein and fat in the same meal slow the rise. For people managing their blood sugar, see sugar management and our page on low-carbohydrate diets.
How much do you need?
The standard recommendation from the US National Academies is that carbohydrates provide 45 to 65% of daily calories, with a minimum of 130 grams a day for adults, mainly to fuel the brain. Within that range, quality counts most: vegetables, fruit, beans and whole grains rather than sugary drinks and refined snacks.
Sources
- Dietary Guidelines for Americans, 2025–2030 (US Department of Health and Human Services and US Department of Agriculture)
- Dietary Guidelines for Americans 2025–2030: what changed (Harvard T.H. Chan School of Public Health)
- Glycemic index and glycemic load (Linus Pauling Institute, Oregon State University)
Last reviewed November 2026.