Does glycemic index matter for kids? should i worry about it?

Yes, and No...: ...Yes, it matters: their food should not contain added sugar, and they should not drink juice or sugar-containing drinks. However, when choosing between different fruits, vegetables, or grains, the differences between, say, banana and apple, should be of concern.

Yes: Glycemic index, a measure of how carbs increase our blood glucuse, is one good way of distinguishing healthy carbs from those that stress our sugar/insulin system. Low GI foods are generally healthier for all of us, including children. Simple rule - avoid white sugar/grains whenever possible.