Alan Frischer, MD, MPH
Updated: Feb 5, 2022
Diabetes and pre-diabetes are surging worldwide, and new tools are being developed to help deal with them. The glycemic index is one such tool and is also being used by those who suffer from hypoglycemia, react strongly to sugar, or are simply striving towards a nutritious diet.
The concept of a glycemic index was first developed in 1980 at the University of Toronto. Foods with carbohydrates that break down quickly during digestion and release glucose rapidly into the bloodstream tend to have a high glycemic index. Foods that break down more slowly release glucose more gradually into the bloodstream, and have a low glycemic index. A lower index usually results in a lower demand for insulin, and may improve long-term blood glucose and lipid control. A rapid rise in blood glucose levels, following consumption of foods with a high glycemic index, is great for energy recovery after exercise, or for a person experiencing hypoglycemia. However, it’s not ideal in quantities for day-to- day life.
The glycemic index is calculated by measuring the rise in the blood sugar level two hours after eating. It ranges from 0 to 100:
Foods with a low glycemic index (55 or less) include most fruit, non-starchy vegetables and carrots, beans, nuts, seeds, 100% stone-ground whole grains, pumpernickel bread, rolled or steel-cut oatmeal, oat bran, muesli, barley, bulgur, sweet potato, yam, peas, legumes, lentils, and mushrooms.
Foods with a medium glycemic index (56-69) include white sugar or sucrose, enriched wheat, pita bread, basmati rice, couscous, boiled unpeeled potato, raisins, prunes, sweet potato, and banana.
Foods with a high glycemic index (70 and above) include glucose, high fructose corn syrup, white bread or bagel, white rice, instant oatmeal, corn flakes, most non whole grain breakfast cereals, maltose, white potato, white pasta, and other highly processed carbohydrates like white flour tortillas, chips, pretzels, rice cakes, popcorn, and saltine crackers.
Interestingly, some foods considered to be unhealthful can have a low glycemic index, like chocolate cake (38) and ice cream (37), and pure fructose (19). Foods like potatoes and rice have a glycemic index around 100, yet they’re a staple of the diet in some countries that have very low rates of diabetes. The science is far from straightforward.
Why adopt a diet focusing on low glycemic foods? They reduce the risk of developing type 2 diabetes, coronary heart disease, and age-related macular degeneration. Research is ongoing regarding other diseases, and on the benefits for pregnant women and their babies. Weight loss is easier when carbohydrates in the low glycemic range replace saturated fats. Many weight loss diets now incorporate the glycemic index, including the South Beach Diet and Nutrisystem.
The glycemic index can be a useful tool. Use common sense - many nutritious foods have a higher glycemic index than do foods with little nutritional value (oatmeal has a higher glycemic index than chocolate!). Eating a food with a high glycemic index alongside a food with a low index can balance out the effect on blood glucose. Be reasonable, exercise moderation, and enjoy your good food!