This post was written by Liz Berkey, MS, RDN, LD, CDCES, BC-ADM, diabetes specialist.
Managing blood sugar is an essential aspect of living with diabetes, and it requires understanding the role different foods play in altering glucose levels. Below, we examine two handy resources to help guide your food choices for diabetes-friendly cuisine.
What is glycemic index?
The glycemic index (GI) is a system that measures how quickly the body digests carbohydrates and their impact on blood sugar levels after eating. First discovered in 1981, this methodology ranks foods on a scale from 0 to 100 and sorts them into three categories:
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Low GI: < 55
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Moderate GI: 56-69
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High GI: > 70
Foods with high glycemic index tend to raise blood sugar more quickly and for longer. Regularly consuming these foods can increase the risk of developing conditions like obesity, diabetes and heart disease.
What affects the glycemic index of foods?
Several factors influence the glycemic index of foods by either slowing down or speeding up the digestion of carbohydrates. Meals containing fiber, vinegar, protein and healthy fats delay the digestion of carbohydrates, helping you feel full for longer and preventing a sudden increase in blood sugar levels.
The particle size and type of sugar molecule also impact digestion. Complex carbohydrates are broken down from long-chain polysaccharides like starches and fibers to disaccharides (e.g., lactose, sucrose, maltose and trehalose). These simple sugars are converted once more to monosaccharides (e.g., glucose, galactose and fructose) and then absorbed by the body as glucose.
Some additional contributors that can affect digestion include:
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Ripeness: As fruits mature, their sugar content increases. For instance, a ripe banana has a higher GI than an unripe one because the starch naturally breaks down into simple sugars.
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Cooking method and time: Cooking food for long periods or using certain methods can increase GI. For example, boiling pasta for an extended time breaks down the carbohydrates more, resulting in a higher GI.
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Storage conditions: Storing food at different temperatures or for varying durations changes its structure and digestion rate. Cold-stored cooked potatoes have a lower GI than freshly cooked ones because the starch is less digestible after cooling.
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Processing: Heavily processed foods, like white bread or sugary cereals, digest rapidly and cause quicker blood sugar spikes, whereas minimally processed options, such as whole grains or vegetables, digest more slowly.
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Food order: Consuming protein, fat or fiber-rich foods before starchy foods slow the absorption of carbohydrates and reduces post-meal blood sugar spikes.
Limitations of glycemic index
Although the glycemic index is a valuable resource for understanding how carbohydrates affect glucose levels, it does have one setback. The glycemic index does not take into account the amount of carbohydrates consumed in a meal. This is where the glycemic load (GL) comes in as an additional tool for assessing food choices.
glycemic load is calculated by multiplying the number of grams of carbohydrates by the glycemic index, then dividing by 100. This approach classifies foods as:
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Low GL: < 10
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Intermediate GL: 11-19
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High GL: > 20
For example, if a food contains 15 grams of carbohydrates and has a glycemic index of 70, determining glycemic load looks like this:
(15 g x 70 GI) ÷ 100 = 10.5 GL.
The above rating places the food near the intermediate GL range, which indicates a moderate impact on blood sugar.
For a more detailed list of common foods and their glycemic index and load values, check out this glycemic index Guide.
Final thoughts
Using the glycemic index and the glycemic load together helps provide a clearer understanding of how food affects blood sugar, which can help minimize diabetes-related post-meal hyperglycemia. If you have additional questions or concerns about managing diabetes, call Parkview Diabetes Care Services at 260-373-4280 to speak with a diabetes educator, registered dietitian or lifestyle change specialist.
Sources
Demirkesen-Bicak, Hilal, et al. “Effect of different fermentation condition on estimated glycemic index, in vitro starch digestibility, and textural and sensory properties of sourdough bread.” Foods, vol. 10, no. 3, 1 Mar. 2021, p. 514, https://doi.org/10.3390/foods10030514.
Murillo, Serafin, et al. “Culinary strategies to manage glycemic response in people with type 2 diabetes: A narrative review.” Frontiers in Nutrition, vol. 9, 10 Nov. 2022, https://doi.org/10.3389/fnut.2022.1025993.
Shkembi, Blerina, and Thom Huppertz. “glycemic responses of milk and plant-based drinks: Food matrix effects.” Foods, vol. 12, no. 3, 18 Jan. 2023, p. 453, https://doi.org/10.3390/foods12030453.
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