My mum sent me a video where they described a study that found that ADHD symptoms improved when parents stopped giving their kids food with red food dye in it. I consulted the literature and couldn't find the aforementioned study, but some studies say there is a link, but still lots of unknowns.
I wish she didn't take health advice from random people on the internet. The psychiatrist they mentioned in the study is known to be a bit of a snake oil physician.