What Is Glycemic Index? Understanding Low vs. High Glycemic Foods

Read on to learn about the relationship between the glycemic index and diabetes and how you can support your blood sugar by making informed choices about what — and how — you eat.

What Is the Glycemic Index?

The American Diabetes Association recommends that people with diabetes keep blood sugar levels under 180 mg/dL between one and two hours after eating. 

Glycemic index is a measure of how quickly a food causes your blood sugar levels to rise. This is determined by how fast your body converts carbohydrates into glucose. Foods are ranked on a scale of zero to 100. A zero rating means the food doesn't increase blood sugar levels after you eat it, while a rating of 100 means the food causes blood sugar levels to increase rapidly.

Generally speaking, foods with a rating of 55 and lower are considered low glycemic, and foods with a rating of 70 and higher are considered high glycemic. While glycemic index isn't a perfect system, it is a good tool to help identify lower glycemic carbohydrates that are also likely to be more nutrient-dense. That said, other factors such as portion size as well as what foods you pair with carbohydrates factor into their impact on blood sugar. Experts refer to this concept as glycemic load.

High Glycemic Index Carbohydrates

Here are some examples of high glycemic index carbohydrates, which cause blood sugar levels to increase more quickly:

• White bread
• White rice
• Rice cakes
• Pancakes
• Baked and mashed potatoes
• Overripe bananas
• Watermelon

Low Glycemic Index Carbohydrates

These low glycemic carbohydrates are converted into glucose more slowly, which can help minimize blood sugar spikes:

• Legumes, such as beans, lentils and chickpeas
• Boiled yams
• Peanuts and cashews
• Pears
• Grapefruit
• Cherries
• Apples
• Barley
• Raw carrots
• Greens, such as spinach, asparagus and kale

Which Factors Influence the Glycemic Index?

Here are some factors that influence how foods affect blood sugar levels:

• Protein, Fiber & Fat Content: Consuming carbohydrates along with protein and fiber can lower the glycemic index of a meal. Fat slows digestion, so foods that contain more fat convert carbs into glucose more slowly.
  
  
• Ripeness: The more ripe a fruit or starchy vegetable, the higher its glycemic index.
  
  
• Preparation: Adding vinegar, lemon or lime to increase the acidity of starchy foods may also lower their glycemic index.
  
  
• Balance: The glycemic index is calculated for individual foods. When you combine several foods at mealtime it changes the overall effect on your blood sugar.

Understanding the Glycemic Index and Diabetes

If you live with diabetes, regulating your blood sugar is essential to maintaining long-term health. Well-managed blood sugar can mean the difference between living a long, healthy life with diabetes and encountering complications such as vision loss, stroke and kidney disease.

The glycemic index isn't a perfect science, but it can be a helpful tool to support informed choices about what and how you eat to help you achieve healthier blood sugar levels. For example, pair high glycemic foods with fat, fiber and protein; squeeze a lime over fresh mango; or choose a just-ripe banana over an overripe one. Simple changes like these can help you better manage your diabetes.