Carbohydrates and the Human Body
All foods provide the human body with at least one of three macronutrients: carbohydrates, proteins, and fats. Of the three macronutrients, the human body prefers carbohydrates as its primary source of fuel for supplying the body’s cells, tissues, and organs with energy. Carbohydrates can come from many different foods, including:
- Vegetables (specifically starchy vegetables, like potatoes and corn)
- Fruits
- Grains (such as pasta, bread, and rice)
- Legumes (beans, peas, and lentils)
- Dairy products
- Desserts and pre-packaged snack foods
Carbohydrates consumed through meals or snacks can be further categorized into three main types:
- Sugars
- Starches
- Fiber
The body breaks down the components of carbohydrates, particularly sugars and starches, further into simple sugars, known as glucose. Fiber, while an important nutrient, cannot be digested in the human body. For this reason, fiber slows the rate at which sugars and starches are broken down into glucose.
As carbohydrates are digested, the pancreas secretes insulin in response to rising blood glucose levels. Understanding how quickly certain carbohydrates are digested and how they affect blood glucose levels can help individuals manage their diabetes.
What is Glycemic Index and Glycemic Load?
Glycemic Index
The glycemic index (GI) was developed to measure how quickly carbohydrate-containing foods raise blood glucose levels after consumption. The glycemic index scale ranges from 0 to 100, and food rankings typically fall into low, medium, and high categories. The categories are:
- Low GI: 0 to 55
- Medium GI: 56 to 69
- High GI: 70 to 100
Foods within the high GI category usually contain more simple sugars and refined carbohydrates. These foods can cause rapid increases in blood glucose. Examples of foods within the high GI category include:
- Refined, white bread
- White rice
- Baked potato
- Watermelon
Medium GI foods typically raise blood glucose more slowly than high GI foods. Foods that fall in the medium GI range also provide more sustained energy, whereas high GI foods often lead to energy crashes and hunger. Many foods are classified as medium-GI foods. Some examples are:
- Whole wheat bread
- Raisins
- Honey
Low GI foods raise blood glucose levels slowly. Most non-starchy vegetables and legumes fit into this category. Other low GI foods are:
- Quinoa
- Strawberries
- Apples
- Cow’s milk or unsweetened plant-based milk alternatives
- Unsweetened Yogurt
The drawback of using a tool like GI is that it relies solely on eating foods on an empty stomach. It does not consider portion size or whether the food was prepared as part of a balanced meal. A food’s GI can also be affected by how the food was cooked (steamed, baked, boiled, etc.), its ripeness, the fiber content, and the food’s fat, fiber, and acid content. However, GI remains a useful tool for identifying nutrient-dense foods with a lower impact on blood glucose levels.
Glycemic Load
Glycemic Load (GL) was developed by researchers to account for the impact of typical food portion sizes on blood glucose levels. Like GI, the GL of foods is classified into three categories:
- Low GL (0 – 10)
- Medium GL (11-19)
- High GL (20 or more)
Some foods are listed as having a high GL, while others may have a medium or low GL. In combination with the GI scale, one can begin to determine the impact of their food choices on diabetes self-management. A low GL means the food has a small overall effect on blood glucose, a medium GL reflects a moderate rise, and a high GL indicates a larger, faster increase. GL considers both how quickly carbohydrates are digested and how many carbohydrates are in a portion, so some foods with a higher GI still fall into the low GL category. In general, following a low GI eating pattern can help support good blood glucose management and overall health.
Benefits of Eating Foods with a Low GI
Regularly eating low-GI foods can aid weight loss or weight management, help balance blood glucose levels, and reduce the risk of chronic diseases such as heart disease and diabetes.
Who Might Benefit the Most from Using GI?
While anyone can use GI to make informed food choices, certain populations may find it especially helpful. These include:
- People living with diabetes
- Individuals with prediabetes or insulin resistance
- People aiming for weight management
- Athletes and active individuals
- Individuals with cardiovascular risk factors, such as a family history of hypertension, high cholesterol, or heart disease.
Overall, GI can be a practical guide for anyone looking to make balanced carbohydrate choices.
Why is this Important for People Living with Diabetes?
GI is important for people living with diabetes because it helps predict how quickly different carbohydrate-containing foods will raise an individual’s blood sugar. Foods with a high GI may cause a more rapid rise in blood glucose, making it harder to manage blood sugar levels. On the other hand, foods with a low GI lead to slower, steadier increases that support better blood sugar control. As a result, not all carbohydrates may affect the body in the same way. However, because diabetes is an individualized disease, with no two people presenting with exactly the same symptoms or outcomes, it is important to follow regular monitoring practices to see how specific foods may affect blood sugar.
Tips for Using GI in Diabetes Management
While GI can help illustrate how different foods may influence blood glucose, it can be difficult to fully understand how to apply this information in daily eating habits. One helpful approach is to use GI as a general guide when comparing similar foods, such as swapping a higher-GI food for a lower-GI one. Additionally, paying special attention to how foods are prepared can be beneficial, as cooking methods, ripeness, and processing can alter a food’s glycemic impact. Another simple strategy is to combine foods rich in carbohydrates with sources of fiber, protein, and/or healthy fats, which can help create meals that digest more gradually. Also, it is important to be mindful of how much carbohydrate is consumed at one time, as GI does not accurately reflect portion sizes.
Overall, using the GI can help complement balanced meals, consistent eating routines, and guidance from healthcare professionals. When used this way, GI can help support more predictable glucose patterns without requiring strict rules or major changes to familiar foods.
Conclusion
Understanding GI can help individuals make more informed choices about the carbohydrates they eat. While it is not meant to replace portion awareness or personalized guidance from registered dietitians, GI can help support steadier glucose levels and overall well-being. By choosing lower-GI foods, pairing carbohydrates with fiber, protein, and healthy fats, and paying special attention to how food is prepared, people can have well-balanced meals that promote their long-term health.
Additional Resources for Nutrition and Diabetes
- HGIC 4406 Nutrition Recommendations for Diabetes (link)
- HGIC Blog Post Carbohydrates: The Good, The Bad, The Healthy (link)
- Stirring Up Healthy Recipes, Culinary Techniques Guide (link)
References:
- Arkansas Heart Hospital. (n.d.). Glycemic Index Chart. https://www.arheart.com/wp-content/uploads/2024/02/2020.10.06-Glycemic-Index-Handout.pdf.
- Cleveland Clinic. (2025, April 15). What is the Glycemic Index? https://health.clevelandclinic.org/glycemic-index.
- Ellis, E. (2019, November 19). What is Glycemic Index? https://www.eatright.org/health/wellness/diet-trends/what-is-glycemic-index.
- Harvard T.H. Chan School of Public Health. (2026). Carbohydrates and Blood Sugar. The Nutrition Source. https://nutritionsource.hsph.harvard.edu/carbohydrates/carbohydrates-and-blood-sugar/
- Mayo Clinic. (2025, August 19). Low-glycemic index diet: What’s behind the claims?https://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/in-depth/low-glycemic-index-diet/art-20048478.
- MedlinePlus. (2024, October 11). Glycemic index and diabetes. U.S. National Library of Medicine. https://medlineplus.gov/ency/patientinstructions/000941.htm.
- U.S. Department of Veterans Affairs. (2024, May 1). Whole Health Library: Glycemic Index. https://www.va.gov/WHOLEHEALTHLIBRARY/tools/glycemic-index.asp.
Authors:
- Hannah Davis, UPIC Intern, Rural Health and Nutrition Extension
- Julianna Lyle, Rural Health and Nutrition Extension Agent, Anderson & Abbeville Counties
Reviewed by:
- Hannah Wilson, PhD, RDN, LD, FAND, Assistant Professor, Community Nutrition, Department of Food, Nutrition, and Packaging Sciences
- Melissa Bales, Extension Associate, Rural Health and Nutrition
