Back in mid-March, I wrote about a study published in the British Journal of Nutrition that slammed the glycemic index. Now the good folks at the Glycemic Index Newsletter have themselves responded to the study (see last item) with a critique of study methods. They cover three essential points:
- The Food Frequency Questionnaire (FFQ) used in the study is an unreliable measure of carbohydrate intake.
- The FFQ was invalid as a measure of the GI values of the foods eaten.
- “The cross-sectional, rather than prospective, nature of the Insulin Resistance Atherosclerosis Study.”
I made the first two points in my post a month ago. The third point is a little fuzzy to me — I need to bone up on my scientific population study lingo, I guess. But maybe a reader can make heads or tails of it by reading the original GI Newsletter posting, which is worth reading anyway, since it gives more detail than I give here (in the interests of not violating copyright).
I continue to feel that there is a fourth weakness to the study design: that the blood glucose levels of the 800+ participants (not 1000+ as reported in the AP story I originally quoted) were checked only twice over the 5-year period of the study.