Carbohydrate

What Is a Carbohydrate?

Carbohydrates are organic molecules composed of carbon, hydrogen, and oxygen. They are the body's primary and preferred source of energy, providing 4 kilocalories per gram. Carbohydrates are classified by their chemical structure into simple sugars (monosaccharides and disaccharides) and complex carbohydrates (oligosaccharides and polysaccharides such as starch and dietary fiber).

Once digested, most carbohydrates are broken down into glucose, which enters the bloodstream and is used for immediate energy or stored as glycogen in the liver and muscles for later use.

Types and Quality

Not all carbohydrates affect the body equally. The glycemic index (GI) ranks carbohydrate-containing foods by how rapidly they raise blood glucose:

• High-GI foods (white bread, glucose, white rice): cause rapid blood sugar spikes
• Low-GI foods (legumes, most fruits, oats): produce a slower, more sustained glucose release
• Fiber-rich complex carbohydrates support gut health and satiety

Recommended Intake and Food Sources

The Acceptable Macronutrient Distribution Range (AMDR) for carbohydrates is 45–65% of total daily energy intake. For a 2,000 kcal diet, this equals roughly 225–325 g per day. The Dietary Guidelines recommend emphasizing whole grains, fruits, vegetables, and legumes over refined or added-sugar sources.

• Brown rice (1 cup cooked): ~45 g carbohydrates
• Banana (medium): ~27 g carbohydrates
• Black beans (1 cup cooked): ~41 g carbohydrates
• Oats (1/2 cup dry): ~27 g carbohydrates