The Glycemic Index (GI) is a ranking system from 0 to 100 for carbohydrate-rich foods that indicates to what degree they raise blood sugar right after they are eaten. A low-number food is one that is digested slowly, thus producing a mild or steady rise in blood sugar, hence the better it supposedly is for weight management and disease control. However, researchers at Tufts University say it is an unreliable measure for managing diabetes. In this study, the researchers checked blood sugar responses in 63 healthy adults after eating the same amount of white bread three different times during 12 weeks. If someone eats the same amount of the same food three times, their blood glucose response should be similar each time. But that is not what happened. The researchers found that even under highly standardized conditions, glycemic index values varied an average of 20% in the same person and 25% between the study’s participants.
Elizabeth Somer, M.A.,R.D.
Matthan N, Ausman L, Meng H, e al: Estimating the reliability of glycemic index values and potential sources of methodological and biological variability. American Journal of Clinical Nutrition 2016; September 7th.