Glycemic Index and Your Diet

People use many tools to create a healthy diet or to lose weight. One of these tools is the glycemic index. The glycemic index (GI) is a way to measure how fast the carbohydrates in a food will make your blood sugar rise. The goal is to eat more foods that have lower GI values. These foods are often more nutritious and better for you.

Path to improved health

The glycemic index was developed to help people who have diabetes control their blood sugar. The GI focuses on carbohydrates in foods. Carbohydrates are a nutrient. When you eat them, your body breaks them down (digests them) into a type of sugar called glucose. Your blood carries the glucose to your cells. Different carbohydrates affect the body in different ways. Some break down and enter the blood quickly, while others break down slowly. Typically, foods with carbohydrates that break down quickly are less nutritious.

The GI assigns a number to foods that contain carbohydrates. The number is based on how much the food raises blood glucose levels, compared to pure sugar. The scale goes from 0 to 100. Pure glucose has the highest GI, with a value of 100.

Foods on the index are divided into 3 categories: low GI, moderate GI, and high GI. Foods with a low GI value increase glucose in your blood slowly. Those with a high value increase glucose quickly.

Low GI foods (value of 1 to 55)

• Many fruits, including apples and grapefruit
• Most legumes, nuts, and beans
• Milk and yogurt
• Bran cereals
• Steel-cut or rolled oats
• Quinoa, bulgur, or barley

Moderate GI foods (value of 56 to 69)

• Sweet corn
• Bananas or raw pineapple
• Raisins
• Oat cereals
• Multigrain, oat bran, or rye bread
• Brown rice or couscous

High GI foods (value of 70 or higher)

• White rice
• White bread and bagels
• Potatoes
• Many processed foods
• Most snack foods

When using the index to plan your meals, choose foods that have a low or medium GI value. If you do include a high GI food, combine it with low GI foods. This will balance out the effect on your blood glucose level.

Things to consider

There are some things you need to think about when using the GI to plan your meals.

• Different forms of the same food can have different GI values. This can depend on certain factors, including:
  • The level of cooking a food can change its value. For example, pasta cooked al dente has a lower GI than pasta cooked to softness.
  • Foods that are processed have higher GI values. For example, instant oatmeal or instant mashed potatoes have higher values than rolled oats or a whole potato.
  • The GI of some fruits, such as bananas, goes up as they ripen.
• Portion size matters. The GI value does not reflect the number of calories in the food. Some foods have a low GI value but have a lot of calories, such as whole milk. These foods should still be eaten sparingly.
• GI value doesn’t reflect nutritional value. Some foods that have high GI values still contain healthy nutrients. For example, potato chips have a similar GI value to green peas. But green peas contain more nutrients. They’re a far better food choice than chips.

Studies have shown mixed results on how effective the GI is for weight loss. The key is to remember to use it as a tool in maintaining a healthy diet, not as the only way to eat.

As you plan your diet, be sure to discuss it with your family doctor who may also refer you to a dietician. They will be able to guide you in a way that will work best for you.

Questions to ask your doctor

• Is the glycemic index good to use as a diet?
• How do I incorporate the glycemic index into a healthy eating pattern?
• Can I eat as much as I want of low GI foods?
• What do I need to watch out for if I use the GI in my diet?

Resources

National Institutes of Health, MedlinePlus: Glycemic index and diabetes