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What Are Carbohydrates?

Medically reviewed by: Melanie L. Pitone, MD

Carbohydrates (car-bo-HI-drates), often called carbs, are one of the three main nutrients in food (along with fat and protein). The body breaks carbohydrates down into sugars — the major source of energy for the body.

Carbohydrates can be split into three groups: sugars, starches, and fiber. All are part of a healthy diet.

What Are Sugars?

Sugars are the simplest form of carbs, meaning they're very easy for your body to digest and give you quick energy. They're also called simple carbohydrates or simple sugars, and they're found in foods like:

  • fruit
  • honey
  • milk
  • candy
  • soda, juice, and other sweet drinks
  • cookies, cakes, and pastries

Some foods with simple sugars are healthier than others. Whole fruits are some of the healthiest foods you can eat, because they're loaded with fiber, vitamins, and minerals.

But candy, soda, and other sweet treats have lots of sugar added to them and almost no fiber or other nutrients. It's OK to eat these things sometimes, but added sugar in big amounts isn't healthy.

What Is Starch?

Starch is a complex carbohydrate. When you eat starch, your body needs to break it down into glucose (a type of sugar) before it can be used for energy. Starches are found in foods like:

  • fruit
  • vegetables
  • grains (like wheat, rice, or oats)
  • legumes (like beans, lentils, or peas)

Like sugars, starches are found in both healthy and unhealthy foods. For instance, white bread and white rice are refined grains, meaning part of the grain is removed and fiber, vitamins, and minerals are lost. What's left is mostly starch. It's best not to eat too much white bread or white rice, because they're low in other important nutrients.

But whole grains, like whole-wheat bread or brown rice, have all their nutrients and are a healthier choice. You're also less likely to overeat whole grains than refined grains because the fiber and other nutrients in whole grains help keep you full.

What Is Fiber?

Like starch, fiber is a complex carbohydrate. But unlike starch, fiber can't be digested. When you eat fiber, it passes through your body, helping to slow down your digestion and keep you full. Foods with fiber include:

  • fruits
  • vegetables
  • whole grains (like whole-wheat bread or brown rice)
  • legumes

While fiber is considered very healthy, some foods with fiber aren't so healthy. For instance, you may find cookies or pastries that say they're "made with whole grains," but that doesn't mean they're healthy. The healthiest way to eat fiber is from whole foods, like whole fruits or vegetables, not processed foods that say they have whole grains or fiber added to them.

How Does the Body Use Carbs?

When you eat carbs, your digestive system breaks them down into sugars, which are absorbed into the bloodstream. As your blood sugar rises, your pancreas releases a hormone called insulin. Insulin moves sugar from the blood into the cells, where it gets used as energy.

When you eat a lot of sugar, this process happens very fast because your body doesn't need to break it down. This is why you might feel an energy spike after eating candy or sugary treats, but then your energy quickly drops and you feel hungry again.

But your body needs more time to break down starch, so when you eat foods like vegetables or whole grains, you don't get a spike in your blood sugar. And when you eat foods with lots of fiber, you'll feel full longer and have more lasting energy. For instance, even though fruit has sugar, it also has fiber, so it's a great choice for quick energy that lasts.

It's OK to treat yourself with candy and sweet treats sometimes. Just make sure you're eating a balanced diet with plenty of healthy carbs like fruit, vegetables, whole grains, and legumes.

Medically reviewed by: Melanie L. Pitone, MD
Date reviewed: April 2024