The Different Types of Carbohydrates

How Simple Carbs and Complex Carbs Affect Blood Sugar

oatmeal and fruit

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Keeping track of your intake of carbohydrates, or carbs, is a key tool for managing diabetes. It's important to know the difference between the two types of carbs. Simple carbs are found in everything from table sugar to fruit, while complex carbs, or starches, come from whole grains and vegetables like sweet potatoes.

Each type of carb increases blood sugar levels but not in the same way. So whether you're managing carbs by counting them, or watching your meals using the MyPlate method or another plan, you should know the effects of each type of carb on your body.

This article explains how simple and complex carbs work. It offers information to help you control your blood sugar levels, keep a healthy weight, and prevent diet-related complications.

healthier carbs for diabetes management

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Carbohydrates 101

Carbs, along with protein and fat, are the three main nutrient groups in the food we eat. During digestion, all three are broken down into elements the body can use for energy. Protein is reduced to amino acids and fat breaks into fatty acids, both of which are stored for future use.

Carbs are different. They are broken down into sugars that, after making a quick stop in the liver, go into the bloodstream and become an immediate source of energy for the body's cells to use. This is why eating carbs can affect blood sugar levels so quickly and dramatically.

It's also why people with diabetes, especially type 2, need to keep tabs on the carbs they eat. In this disease, either the pancreas does not produce enough insulin to keep blood sugar levels in check, or the body doesn't respond correctly to insulin. In both cases, sugar (glucose) can build up in the bloodstream.

Simple Carbs

Simple carbs have, as the name suggests, a very basic chemical structure. They may be monosaccharides, which are made up of a single sugar molecule, like glucose. Or they may be disaccharides, which have two simple sugars linked together, as with lactose (milk sugars).

Simple carbs are fairly easy for the body to digest. Enzymes in the small intestine break them down before they enter the bloodstream. Any sugar that isn't used right away is stored as fat, and that's why eating foods with lots of added sugar can add to weight gain.

Examples of Simple Carbs

Many foods contain simple carbs and are rich sources of vitamins, minerals, and other nutrients. These foods should be a part of a diabetes-friendly diet. Examples include:

  • Fruit
  • Dairy products
  • Some vegetables

However, not all simple sugars are digested at the same rate. Whole fruit contains fiber, so fructose—the simple sugar in it—is absorbed more slowly in the body. This may have less impact on blood glucose levels than other sugar sources do.

The added sugars in syrups, cookies, and many other processed foods are also simple carbs. But these tend to be "empty calories" with little nutritional value, and they more easily lead to weight gain and health problems like heart disease. Added sugars should be avoided in a healthy diet.

Complex Carbs

Complex carbs are made of longer, more complex chains of sugar molecules. These are called oligosaccharides and polysaccharides. Complex carbs take longer to digest than simple carbs do. This means they have a less immediate impact on blood sugar, causing it to rise more slowly.

Examples of Complex Carbs

Some complex carbs are better choices than others. The healthiest complex carbs are those that have not been processed or refined, and include:

  • Whole grains such as brown rice, wild rice, oatmeal, and whole-grain (rather than pearled) barley
  • Grain-like foods such as quinoa (a seed) and buckwheat (a grass)
  • Starchy vegetables including potatoes, sweet potatoes, and corn
  • Non-starchy vegetables, which includes everything from asparagus to zucchini
  • Beans and legumes like lentils, kidney beans, and chickpeas

Note that all of these foods are excellent sources of fiber. Fiber helps keep blood sugar levels from spiking too high, helps control cholesterol levels, and is important for digestive health.

With complex carbs, it's best to avoid or limit refined grains and processed foods made with them. "Refined" means two of the three elements of each kernel of grain—the bran and the germ—have been removed, along with the fiber, healthy fats, and nutrients found in them.

The part of the kernel that's left is the starchy endosperm. It has less fiber and nutrients, even though vitamins and minerals sometimes are added back into refined grains. Products made with them are sold as "enriched" but there really is no substitute for the natural grains.

Processed foods made with refined grains include:

  • Bagels
  • Cakes, cookies, and other baked goods
  • Cereals made from refined grains
  • Crackers
  • Hamburger or hot dog buns
  • Pancakes and waffles
  • Pizza dough
  • Rice snacks
  • Soft sandwich bread 
  • White rice and pasta

Note that many of these foods are also sources of added sugar, making them even less ideal for managing blood glucose.


Carbohydrates, fats, and proteins make up the main nutrients in our food. Some carbs are simple, and they are quickly broken down into sugars that enter the bloodstream. Other carbs are more complex and release sugars more slowly, which makes it easier to avoid big changes in glucose levels.

Balancing Simple and Complex Carbs

How people respond to specific types of carbs, or even to individual foods, can vary widely. This is one reason for why there's no one-size-fits-all diet for treating diabetes.

That said, when planning meals and snacks, it's best to focus on getting your carbs—both simple and complex—from natural, unrefined, and unprocessed sources. These include fresh fruits and vegetables, whole grains and products made with them, low-fat dairy products, and legumes.

You'll know that you're getting nutrient-rich foods that are high in fiber and low in calories and saturated fat. They are more likely to help you control your blood sugar and manage your diabetes.

Not everyone who is "watching their carbs" is doing so because of diabetes. Yet everyone who chooses fresh fruits and whole grains, while avoiding processed foods, may see the overall benefits of keeping a healthy and balanced mix of carbs.


Carbs are necessary for a healthy diet, but all carbs increase blood sugar. So if you have diabetes, it's important to watch your carbs and choose healthy sources.

Simple carbs increase blood sugar quickly. They are found in some healthy foods such as fruits and vegetables, but also in processed foods with added sugars.

Complex carbs are absorbed slowly and increase blood sugar less dramatically. Many whole foods that contain them include other nutrients like fiber and vitamins. However, it's best to limit starchy refined grains.

A Word From Verywell

Most people want to choose healthy foods for themselves and their families, and it helps to know how carbohydrates work. That's especially true for people with diabetes because not all carbs are the same. Knowing the difference between simple and complex carbs will help you keep your blood sugar levels, and your life, in better balance.

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6 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  2. Ferretti F, Mariani M. Simple vs. complex carbohydrate dietary patterns and the global overweight and obesity pandemicInt J Environ Res Public Health. 2017;14(10):1174. doi:10.3390/ijerph14101174

  3. Centers for Disease Control and Prevention. Know your limit for added sugars.

  4. American Heart Association. Carbohydrates.

  5. U.S. Department of Agriculture. Dietary guidelines for Americans, 2020-2025.

  6. Ludwig DS, Hu FB, Tappy L, et al. Dietary carbohydrates: role of quality and quantity in chronic diseaseBMJ. 2018;361:k2340. doi: 10.1136/bmj.k2340

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