Understanding the impact of dietary carbohydrates on blood sugar levels is essential for managing various health conditions and preventing disease complications. In the last 20 years, the number of adults diagnosed with diabetes has more than doubled, calling for the urgent need for effective preventive and treatment strategies.
While the concept of glycemic index has long been used as a measure of how quickly foods raise blood glucose levels, glycemic load offers a more comprehensive approach to assessing the glycemic impact of foods. By having a deeper understanding of glycemic load, individuals can make informed decisions to support blood sugar control and overall metabolic health.
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What Is Glycemic Load?
Glycemic load (GL) is a measurement that considers the quantity and quality of carbohydrates in a portion of food to reflect how that food affects blood sugar levels.
Understanding glycemic load is valuable for anyone seeking to optimize their dietary choices for overall health and wellness. Selecting foods that have a lower impact on blood sugar levels aids in blood sugar control, satiety, and weight management and plays a role in preventing and treating chronic diseases, such as type 2 diabetes, metabolic syndrome, and obesity.
How to Calculate Glycemic Load
To calculate a food's glycemic load, multiply its glycemic index (GI) by the amount of carbohydrates in a serving, and then divide by 100. The formula for calculating glycemic load is:
Let's walk through an example of calculating GL using an apple.
The GI of an apple is approximately 36.
A medium-sized apple contains about 14 grams of carbohydrates.
To calculate the GL of an apple, you would enter these numbers into the above equation:
Doing the math, you'll see that one medium apple's GL is 5.
A glycemic load of 5 is considered low. This means that consuming a medium-sized apple is unlikely to cause a significant spike in blood sugar levels. Instead, the carbohydrates in the apple are digested and absorbed slowly, leading to a more gradual, modest increase in blood sugar.
What Is the Difference Between Glycemic Index and Glycemic Load?
The GI is a numerical scale (0-100) that measures how quickly a carbohydrate-containing food raises blood sugar levels compared to a reference food (generally pure glucose). It indicates the quality of carbohydrates in a food based on how quickly they cause blood sugar levels to rise.
GI is categorized as follows:
- Low Glycemic Index: 0-55
- Medium Glycemic Index: 56-69
- High Glycemic Index: 70-100
Foods with a high GI are rapidly digested and absorbed, leading to a quick spike in blood sugar, while those with a low GI are digested and absorbed more slowly, resulting in a more gradual increase in blood sugar. (18)
Scientists developed the concept of GL to better describe the quality and quantity of carbohydrates in a food serving. GL is a more functional tool to estimate how quickly a food causes blood sugar to rise and the magnitude of that effect. While both are valuable tools for understanding how foods impact blood sugar, GL may offer a more relevant approach to meal planning than GI because it represents the real-life effect of a particular food portion on blood sugar. (7, 18)
For example, watermelon has a high GI of 76; however, because the amount of carbohydrates in a serving of watermelon is low, watermelon has a low GL. Watermelon's effect on blood sugar is better predicted by its GL value. (7)
What Does Glycemic Load Mean?
Similar to GI, GL has a scale with values categorized as low, medium, or high:
- Low Glycemic Load: 0-10
- Medium Glycemic Load: 11-19
- High Glycemic Load: 20 or higher
For general health and good blood sugar control, it is recommended to eat balanced meals and prioritize foods with low and medium GLs over those with high GLs.
Research supports the inclusion of low-GL foods in preventing and treating various health conditions, including diabetes, obesity, and cardiovascular disease. Let's discuss some of these findings:
Diabetes Mellitus
A meta-analysis that gathered data from three large prospective cohort studies and nearly 600,000 people concluded that high-GL diets are associated with a 10% increased risk of type 2 diabetes.
Conversely, studies show that consuming a diet rich in low-GL foods helps improve glycemic control in individuals with diabetes mellitus. A meta-analysis of 19 randomized controlled trials that included over 800 patients with type 1 and type 2 diabetes found that low-GL diets help meet blood sugar goals, as reflected by reductions in fructosamine and hemoglobin A1c levels.
Additionally, low-GL diets have been linked to reduced risk of developing type 2 diabetes in at-risk individuals. The Mediterranean diet is a well-studied anti-inflammatory and cardioprotective diet correlated with improved cardiovascular outcomes, including glucose control. According to a study published in Diabetologia, integrating the Mediterranean diet with a low-GL diet conferred additional protection against type 2 diabetes, resulting in a cumulative risk reduction of 20%.
Weight Management
Low-GL foods can aid in weight management and obesity prevention by promoting satiety and reducing overall calorie intake. These foods provide sustained energy and help prevent cravings and overeating. (12)
Many traditional weight loss strategies call for adherence to an energy-restricted, low-fat diet. Comparatively, research has demonstrated that a low-GL diet (30-35% of calories from low-GI carbohydrates) is as effective as a low-fat diet (less than 30% of calories from fat) in achieving weight loss during a one-year study period.
Cardiovascular Disease
Risk factors for cardiovascular disease include high blood pressure, high cholesterol levels, and inflammation. Low-GL diets may benefit cardiovascular health by reducing and managing these risks.
A meta-analysis of 14 studies found a 23% increased risk of cardiovascular disease with a high-GL diet. Following a low-GL diet, however, leads to reductions in triglycerides, inflammation (as measured by C-reactive protein), fasting insulin, and blood pressure.
What Is a Good Glycemic Load?
To calculate the GL of a meal, add the GL values for each food component of the meal together. According to the Glycemic Index Foundation, a low-GL meal has a GL of 33 or less. They also recommend keeping the daily glycemic load under 100. (11)
Here are strategies for lowering dietary GL:
- Eat at least five servings of vegetables and 65-100 grams of protein daily. Aim to fill half your plate with non-starchy vegetables and a quarter with lean proteins for each meal.
- Increase consumption of whole grains, nuts, beans, whole fruits, and non-starchy vegetables.
- Reduce consumption of starchy and sugary foods like potatoes, white rice, white bread, cookies, candy, and soft drinks.
- Pay attention to portion sizes. Use measuring cups, food scales, or visual cues to estimate appropriate portions.
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Key Takeaways
- Understanding the concept of glycemic load offers a more comprehensive approach to managing blood sugar levels and overall metabolic health than solely relying on the glycemic index.
- While GI measures the speed of carbohydrate absorption, GL considers both the quality and quantity of carbohydrates in a serving, providing a more nuanced understanding of a food's impact on blood glucose levels.
- By considering GL in dietary choices, individuals, especially those managing diabetes or other metabolic health issues, can make better-informed dietary decisions to support health goals and outcomes.
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