Are there age-related differences in glycaemic response and glycaemic index?

We previously found the glycaemic index (GI) of 3 foods to be similar in subjects aged >40 y (mean 49 y) versus <40 y (mean 29 y), but a more recent study reported the GI of 2 foods to be higher in subjects aged >55 y (mean 70 y) vs. <33 y (mean 24 y). Here, we compared the GI or relative glycaemic response (RGR, analogous to GI but using a different reference food) of the younger (age <33 y) vs. the older (age >55 y) subjects who participated in previously published studies that included n ≥ 9 in each group. Study 1, (GI, 3 foods) had n = 19:9 younger:older subjects; Study 2, (GI, 2 foods) n = 14:10; Study 3, (RGR, 1 food), n = 68:16. The GI or RGR of the 6 foods varied from 36 to 88; none differed significantly in younger vs. older and the overall means were equivalent, 63.2 vs. 63.7, respectively. The GI or RGR values for 5 foods from 3 additional studies not meeting the inclusion criteria above were also similar in younger vs. older subjects. Therefore, we found no evidence from n = 11 comparisons that GI values differ in younger vs. older subjects. However, there are insufficient data to determine if GI values are equivalent in older vs. younger subjects, something that requires a different statistical test.