Glycemic Index Unreliable Indicator of Blood Glucose Response

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Glycemic index values may vary widely for the same foods.
Glycemic index values may vary widely for the same foods.

HealthDay News -- Glycemic index values of the same foods can vary widely and may be an unreliable indicator of blood glucose response, according to a study published online September 7 in the American Journal of Clinical Nutrition.

Researchers checked blood glucose responses in 63 healthy adults after eating the same amount of white bread 3 different times over 12 weeks. The investigators found that glycemic index values varied an average of 20% among individuals and 25% between different study participants.

"Glycemic index values appear to be an unreliable indicator even under highly standardized conditions, and are unlikely to be useful in guiding food choices," lead author Nirupa Matthan, PhD, of the US Department of Agriculture's Human Nutrition Research Center at Tufts University, Boston, Massachusetts, said in a university news release. 

"If someone eats the same amount of the same food 3 times, their blood glucose response should be similar each time, but that was not observed in our study. A food that is low glycemic index for you 1 time you eat it could be high the next time, and it may have no impact on blood sugar for me."

Based on these findings, Dr Matthan said using the glycemic index wasn't practical for food labeling or in dietary guidelines at the individual level.


  1. Matthan NR, Ausman LM, Meng H, Tighiouart H, Lichtenstein AH. Estimating the reliability of glycemic index values and potential sources of methodological and biological variability. Am J Clin Nutr. 2016. doi:10.3945/​ajcn.116.137208.
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