Healthy Carbohydrates: Glycemic Index

  • Carbohydrates represent an important part of a healthy nutrition pattern but what is more important is the type or quality of carbohydrate rather than the amount in the diet.

  • Carbohydrates are everywhere and carbohydrate quality has a significant influence on weight gain, diabetes and cardiovascular risk so choosing healthier high quality carbs is important to our health. The healthiest carbohydrate is found in foods containing unprocessed whole grains, vegetables and beans compared to those found in refined or processed grains, white bread or French fries.

  • Prior terms such as simple or complex carbohydrates are too vague and most research has focused more specifically on how our blood sugar responds to a carbohydrate and the amount of that carbohydrate in a food. That is called a food’s glycemic index and load.

Glycemic Index

The Glycemic Index (GI) is a numerical index that helps us to assess carbohydrate quality based on how quickly blood sugar responds to a particular food. It is now a respected measurement endorsed by many international societies.

Glycemic index (GI) uses a scale of 0 to 100, with higher values given to foods that cause the most rapid rise in blood sugar (pure glucose serves as has a glycemic index of 100 and is the reference to how other foods are ranked). Foods with a lower glycemic index are typically recommended for those wishing to help control appetite and delay hunger and improve blood sugar. This is very important considering current statistics that show that more than one in every two Americans are overweight or suffer from prediabetes and are at risk for type 2 diabetes. Polycystic ovary disease is another so-called insulin resistant condition that can be improved with better compliance with a lower glycemic dietary pattern. Low-GI foods cause a more gradual blood sugar and insulin rise due to slower digestion and absorption and have been shown to improve both glucose and lipid levels in people with diabetes.

The rapid rise in diabetes and obesity has created a need to better communicate the fact that carbohydrates in different foods can have variable affects on blood sugar following meals with important health implications –this is what is meant by carbohydrate “quality”.

Glycemic load

The International Scientific Consensus Summit on Glycemic Index, Glycemic Load and Glycemic Response agreed in 2013 to consider glycemic index and load as a dietary guideline and provide low GI/GL symbols as part of healthy foods package labels. The glycemic load (GL) was popularized by Dr. Walter Willett and associates at the Harvard School of Public Health and is the best tool we have to assess the effect a carbohydrate has on blood sugar and the secretion of the body’s glucose lowering hormone, insulin. Glycemic index can be misleading when trying to compare different foods. Compared to glycemic index (GI) a food’s glycemic load (GL) is a more useful measure for tracking a carbohydrate’s blood sugar effect since it takes into account the amount of carbohydrate in a given serving of a food. For example carrots, have a relatively high GI of 47 but since the amount of carbs in carrots is so low it has a very low glycemic load of 2.

The glycemic load is more useful since it normalizes the glycemic index to the amount of carbohydrate in a food. Said another way, 2 ounces of cotton candy and one and a half cups of vanilla ice cream both contain 50 grams of carbs but it takes 4 cups of carrots to provide the same  50 grams of carbs.

Insulin resistance

Insulin resistance is a physiological condition where the hormone insulin becomes less effective at lowering blood sugar. Insulin resistance is the underlying “problem” found in those with prediabetes, type 2 diabetes as well as those young women with polycystic ovarian syndrome (PCOS). Insulin resistance is a very common condition –about one-third of us have it and for those baby boomers it’s about half of us who have prediabetes.

We need to pay attention to carbohydrate quality to help stem the tide of the developing epidemic of diabetes.

Obesity in U.S. adolescents represents the most important risk factor for insulin resistance and for the development of type 2 diabetes. The prevalence of insulin resistance can vary by ethnicity and may be present even if one is lean. In healthy young lean South Asian Indian men for example, insulin resistance may be 3- to 4-fold more common than lean men of other ethnic groups. According to Dr. Walter Willett, Chairman of the Department of Nutrition at the Harvard School of Public Health “Given essentially conclusive evidence that high GI/GL diets contribute to risk of type 2 diabetes and cardiovascular disease, reduction in GI and GL should be a public health priority.” We have solid evidence that attention to lifestyle and healthier nutrition choices works. The U.S. Diabetes Prevention Program, showed that even modest weight loss through dietary changes and increased physical activity could prevent prediabetes from progressing to diabetes.


Limitation on the consumption of simple or refined carbohydrates (and sugary beverages) and more physical activity are key recommendations for those with insulin resistance, prediabetes or diabetes. Look for products that list the first ingredient as “whole wheat,” “whole oats” or a similar whole grain (remember “multigrain” doesn’t necessarily mean whole grain). Examples of what we mean by low-high glycemic index:

  • Low glycemic index (GI of 55 or less): Most fruits and vegetables, beans, minimally processed grains, pasta, low-fat dairy foods, and nuts.
  • Moderate glycemic index (GI 56 to 69): White and sweet potatoes, corn, white rice, couscous, breakfast cereals such as Cream of Wheat and Mini Wheats.
  • High glycemic index (GI of 70 or higher): White bread, rice cakes, most crackers, bagels, cakes, doughnuts, croissants, most packaged breakfast cereals.

Learn more:

Fiber: Non-digestible and Indispensable

Sugar: the Sweet Truth

What Are Added Sugars and How to