High-Glycemic Index Foods: What This Means

The glycemic index (GI) is a measure of the effect of carbohydrates in a food on changes in blood glucose levels relative to the effect of pure glucose. The reference is the change in blood sugar within two hours after consuming glucose, whose GI is equal to 100. The term was introduced in 1981 by Dr. David Jenkins, a professor at the University of Toronto.

What the glycemic index is and how it is determined

The method is regulated by the international standard ISO 26642:2010. Ten or more healthy volunteers on an empty stomach eat a portion of the food containing 50 grams of carbohydrates within 15 minutes, then for two hours their blood sugar level is measured every 15 minutes and a curve is plotted. The area under this curve is compared with the area after 50 grams of pure glucose. According to the same standard, when determining GI, the rate of change in blood sugar is not measured — yet it is often mistakenly called the index.

Which values are considered high, medium, and low GI

The GI of glucose is taken as 100, and other foods are compared with this reference. For example, the GI of buckwheat is 54, while some foods have a value above 100 — that is, they raise sugar more than pure glucose. The higher the number, the more the sugar level rises after a portion with the same amount of carbohydrates. Carbohydrates with a low GI are digested, absorbed, and metabolized more slowly, causing a smaller and slower rise in sugar levels and, as a rule, insulin.

Which foods have a high glycemic index

According to research from the University of Sydney, foods common in any cuisine can have a GI of 100 or higher:

• white bread — up to 100, corn bread — up to 110;
• cooked white rice — up to 112;
• boiled and baked potatoes — up to 118;
• dry breakfast cereals made from corn flakes — up to 132.

Maltose — 105, maltodextrin in sports and infant nutrition — 105–135 depending on the production method.

Why a high GI does not equal high sugar content

In studies, blood glucose concentration was measured after a portion of a food containing 50 grams of carbohydrates. It turned out that ice cream, despite its high sugar content, raised glucose noticeably less than ordinary bread. Therefore, one cannot judge a food's effect on sugar solely by the amount of sugar in it.

Glycemic index and glycemic load: what is the difference

GI compares the effect of carbohydrates but does not take into account their amount in a portion. Glycemic load is calculated as follows: grams of carbohydrates in a portion are multiplied by GI and divided by 100. In 100 grams of dry buckwheat there are 72 grams of carbohydrates; at a GI of 54, the load will be 72×0.54=39 grams of glucose equivalent. A food with a high GI in a small portion produces a smaller load than it seems from a single number.

When to consider GI and when to consult a doctor

Knowledge about GI is used in diabetes, gestational diabetes mellitus, and polycystic ovary syndrome. In type 2 diabetes, the doctor assesses diet, weight, HbA1c level, cholesterol, blood pressure, and kidney function. The main problem with high-GI foods is their high calorie content: even a small portion usually contains many calories. This is not a treatment recommendation; the diet should be discussed with a doctor or a diabetes nurse.

Eating a high-GI food by itself is not a reason to call an ambulance; 103 or 112 — for a life-threatening condition (such as a stroke or heart attack).

This material is for reference and does not replace a doctor's consultation.

This content is for reference and does not replace a doctor's consultation. Medical disclaimer