I don't have much info but one thing I've read is that one TEASPOON of sugar lowers your immune system for 4 hours.
This is something I've told my girls in explanations about why sugary snacks are just a treat, why they can't have more, etc.
Well, a few weeks ago I had strep throat. And I received quite a lecture from my 5 year old. you see, the weekend before I'd gone to the grocery store hungry and left with 2 packages of oreos. And ate most of them within a couple days. also some more sugar thrown in there I think. So my 5 year old told me that i ate too much sugar, too many of those cookies, and that's why I was sick.