Understanding Different Types of Carbohydrates in Your Diet

Understanding Different Types of Carbohydrates in Your Diet

What Are Carbohydrates? 

Carbohydrates, protein, and fat make up the three major types of dietary macronutrients.1 Carbohydrates are chemically composed of carbon, hydrogen, and oxygen atoms and are broken down into glucose in our digestive system for immediate use as energy or stored in muscle tissue and the liver for future use. The 2020-2025 Dietary Guidelines for Americans (DGA) recommends 45-65% of daily calories or 130 g per day to come from carbohydrates.4

Carbohydrates also play a role in lipid metabolism and fermentation, affect blood glucose and insulin levels, and their intake has been of interest in weight, diabetes, aging, heart health, and gut health-related research.2 Although carbohydrates encompass a broad category of foods, they can be subcategorized into simple and complex carbohydrates.2,3


Simple carbohydrates, or more commonly known as sugars, are monosaccharides (one sugar molecule) and disaccharides (two sugar molecules combined).1 Glucose, fructose, and galactose are the three main types of monosaccharides, and sucrose and lactose are the two main types of disaccharides.2 Sugars, which are easily used as energy, cause sudden rises in blood glucose levels and stimulate insulin secretion. Besides their chemical structure, sugars can be further categorized into natural sugars and added sugars based on their source. 

Sources of Natural Sugars:1,5

  • Milk (lactose)
  • Food products that contain milk (eg, yogurt or cream)
  • Fruits (fructose) 

Sources of Added Sugars:

  • Sugar-sweetened beverages (eg, soda, sports drinks, energy drinks, fruit drinks)
  • Sweetened coffees and teas
  • Desserts
  • Sweet snacks (eg, candies)
  • Sweetened breakfast cereals

Added sugars are frequently found in highly processed foods and the DGA recommends limiting added sugars to less than 10% of calories per day.4


Complex carbohydrates describe oligosaccharides (up to ten sugar molecules combined) or polysaccharides (more than ten sugar molecules combined).1 Unlike simple carbohydrates that are readily absorbed and used by the body, complex carbohydrates take longer to be digested and must first be broken down into sugars. They have a less drastic and immediate effect on blood glucose levels. Besides their chemical structure, complex carbohydrates can further be categorized into starches that can be digested by the body and fibers that cannot be digested. Many foods contain both starches and fibers.

STARCHES – Starches, or complex carbohydrates, are molecules with large numbers of simple sugars combined.1 Grains, starchy vegetables, and beans are primary sources of starches.4 

Sources of Starches:

  • Grains and grain products (eg, wheat, pasta, bread, rice, oats)
  • Starchy vegetables (eg, potatoes, corn, lotus root, lima beans, plantains, water chestnuts, yam)
  • Beans (eg, lentils, peas, chickpeas) 

Grains are further divided into whole grain and refined grain.4,6 Whole grains are not refined, containing all the natural components of grains (ie, bran, germ, endosperm) that are rich in fiber, vitamins, minerals, fatty acids, and starch.6 Refined grains, however, do not contain the outer shells of the grain and provide mostly starches but lack fiber, vitamins, minerals, and fatty acids. The DGA recommends that at least half of total grain intake should come from whole grains.4 

Sources of Whole Grains:

  • Brown rice, wild rice
  • Buckwheat
  • Oats
  • Barley (not pearled)
  • Quinoa
  • Whole-wheat bread, cereals, cornmeal

Sources of Refined Grains:

  • White rice
  • White breads
  • Pasta
  • Barley (pearled)
  • Corn grits
  • Refined-grain cereals and crackers

FIBERS – Dietary fibers are complex carbohydrates that are not digested or absorbed by the human small intestine.7–10 The consumption of dietary fiber has been shown to improve satiety, glucose and insulin responses, and gut hormone and microbiota health.9 The DGA recommends consuming 14 g of dietary fiber per 1,000 kcal of food.4,11 

Sources of Fibers:

  • Vegetables
  • Beans, peas, lentils
  • Whole grains
  • Fruits
  • Cereal bran
  • Flaked cereal
  • Flours


1. Holesh JE, Aslam S, Martin A. Physiology, Carbohydrates. In: StatPearls. StatPearls Publishing; 2023. Accessed June 7, 2023. http://www.ncbi.nlm.nih.gov/books/NBK459280/
2. Cummings JH, Stephen AM. Carbohydrate Terminology and Classification. Eur J Clin Nutr. 2007;61(1):S5-S18. doi:10.1038/sj.ejcn.1602936 3. Blaak EE, Riccardi G, Cho L. Carbohydrates: Separating Fact from Fiction. Atherosclerosis. 2021;328:114-123. doi:10.1016/j.atherosclerosis.2021.03.025
4. U.S. Department of Agriculture and U.S. Department of Health and Human Services. Dietary Guidelines for Americans, 2020-2025. 9th Edition. December 2020. Available at DietaryGuidelines.gov.
5. Sugar 101. www.heart.org. Accessed June 8, 2023. https://www.heart.org/en/healthy-living/healthy-eating/eat-smart/sugar/sugar-101
6. Types of Carbohydrates | ADA. Accessed June 9, 2023. https://diabetes.org/healthy-living/recipes-nutrition/understanding-carbs/types-carbohydrates
7. Lattimer JM, Haub MD. Effects of Dietary Fiber and Its Components on Metabolic Health. Nutrients. 2010;2(12):1266-1289. doi:10.3390/nu2121266
8. Kimura Y, Yoshida D, Hirakawa Y, et al. Dietary Fiber Intake and Risk of Type 2 Diabetes in a General Japanese Population: The Hisayama Study. J Diabetes Investig. 2021;12(4):527-536. doi:10.1111/jdi.13377
9. Mao T, Huang F, Zhu X, Wei D, Chen L. Effects of Dietary Fiber on Glycemic Control and Insulin Sensitivity in Patients With Type 2 Diabetes: A Systematic Review and Meta-Analysis. J Funct Foods. 2021;82:104500. doi:10.1016/j.jff.2021.104500
10. Nutrition C for FS and A. Questions and Answers on Dietary Fiber. FDA. Published online December 15, 2021. Accessed March 1, 2023. https://www.fda.gov/food/food-labeling-nutrition/questions-and-answers-dietary-fiber
11. Evert AB, Dennison M, Gardner CD, et al. Nutrition Therapy for Adults With Diabetes or Prediabetes: A Consensus Report. Diabetes Care. 2019;42(5):731-754. doi:10.2337/dci19-0014



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