What Are Complex Carbohydrates?

Close up of healthy cereal
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Complex carbohydrates provide your body with the energy you need to get up, move around, and do all the things you do every day. They include starch, maltose, and cellulose, and they're found in fruits, vegetables, legumes, nuts, seeds, and grains.

All plant-based foods have different forms complex carbohydrates, mostly some combination of starch and cellulose. Starch is used by plants as a way to store energy.

Grains, potatoes, and rice, peas, legumes and corn are high in starch. Cellulose forms the structures that give plants their shape, and it's the main component of dietary fiber. Vegetables such as green beans, broccoli, and spinach contain less starch, but they have more cellulose. 

The difference between complex carbohydrates and simple carbohydrates is just the size of the molecules. Simple carbohydrates are made up of only one or two sugar units, whereas complex carbs contain at least three sugars. Simple sugars include table sugar, fructose, honey, syrups and so on.

Complex Carbohydrate Digestion and Absorption

Starches are digested and absorbed quickly, so starchy foods like white bread and pasta can result in a blood sugar spike, very much like eating something that's high in sugar. But, your digestive system can't break cellulose apart, which is a good thing because having that non-digestible fiber in your digestive tract slows things down, so the starches don't cause such a big blood sugar spike.

One reason it's important to eat whole grains, colorful veggies and other high fiber foods are too slow down the absorption of sugars and starches.

How Much Complex Carbohydrate Do I Need?

Generally speaking, complex carbohydrates should supply about half the calories in your diet. And adults need from 25 to 38 grams of fiber every day.

You can accomplish both by eating a diet rich in colorful veggies, whole grains, and an assortment of nuts and seeds. 

When planning a meal, think about how the food will be arranged on your plate. Mentally divide the plate into four quarters. Half of the plate should be filled with green or colorful vegetables or fruits and one-fourth of your plate can hold something starchier, such as bread, rice, potatoes or pasta. 

The last quarter is home to your primary protein source -- it can be some meat, poultry or fish, or you can choose a vegetarian protein source such as legumes, or lentils. That should give you the right amounts of carbs, plus keep your proteins and fats in balance. 

A balanced meal with plenty of fiber and healthy carbs could be a generous serving of Swiss chard, one scoop of mashed potatoes, and a piece of grilled salmon that's about the size of the palm of your hand. Or if you prefer to go vegetarian, swap out the fish for some stir-fried tofu.


Centers for Disease Control and Prevention. "Nutrition for Everyone -- Carbohydrates." 

Gropper SS, Smith JL, Groff JL. "Advanced Nutrition and Human Metabolism." Sixth Edition. Belmont, CA. Wadsworth Publishing Company, 2013. 

Office of Disease Prevention and Health Promotion, Office of the Assistant Secretary for Health, Office of the Secretary, U.S. Department of Health and Human Services -- Health.gov. "Dietary Guidelines for Americans, 2010."

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