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What Are Complex Carbohydrates?

Nutrition Q&A


Updated August 07, 2014

Home grown double beans
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Brock asks, "I'm a bit confused by carbohydrates -- what are complex carbohydrates and what foods count as complex carbs? Are whole grains the complex carbohydrates or are they starches?"

Biochemically speaking, complex carbohydrates are made up of at least three single sugar molecules. They include starches, maltose and cellulose. 

The difference between complex carbohydrates and simple carbohydrates is the size of the molecule. Simple carbohydrates are made up of only one or two sugar units. They include table sugar, fructose, syrups and so on.

Plant-based foods have some type of complex carbohydrates. Starch is used by plants as a way to store energy. Starchy foods include grains, potatoes, and rice, peas, legumes and corn. 

When you eat those plants, your digestive system breaks the starches into individual glucose units and your body absorbs them quickly. So even though starch is a complex carbohydrate, it can cause your blood sugar to rise in a short time -- similar to the simple carbohydrates.

Another complex carbohydrate, called cellulose, forms the structures that give plants their shape, and it's the main component of dietary fiber. Any starch from these plants is broken down, but the fiber slows the absorption. That's good because the starches that are there don't have quite as strong of an effect on your blood sugar. 

Vegetables such as green beans, broccoli and spinach contain less starch, but they have more fiber.

Best Complex Carbohydrate Sources

Generally speaking, complex carbohydrates should supply about half the calories in your diet. choose high-fiber vegetables and whole grains as often as possible. You don't really need to focus on the carb counts as long as you eat a variety of plant-based foods. You don't get any starches or fiber from meat or other animal-sourced foods.

When planning a meal, think of 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. One fourth of your plate can hold something starchier, such as bread, rice, potatoes or pasta. The last quarter is home to your main protein source -- it can be some type of meat, poultry or fish, or you can choose a vegetarian protein source such as legumes, or lentils.

For example, a balanced meal with plenty of fiber could include a large 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 salmon for some stir-fried tofu.

Check out my week of healthy meal plans to get you started. Each one includes links to recipes and a grocery list.


Centers for Disease Control and Prevention. "Nutrition for Everyone -- Carbohydrates." Accessed July 8, 2014. http://www.cdc.gov/nutrition/everyone/basics/carbs.html.

Gropper SS, Smith JL, Groff JL. "Advanced Nutrition and Human Metabolism." Fourth Edition. Belmont, CA. Wadsworth Pub Co. 2005.

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. Accessed July 8, 2014. http://www.health.gov/dietaryguidelines/dga2010/DietaryGuidelines2010.pdf.

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