I looked into it & concluded that the evidence of links is very weak. And I haven't noticed any pattern, anyway, other than any food after 8pm tends to make DS harder to settle.
I give DS fish oils but can't know what things would have been like without them. That said, I'm sure it's worthwhile to try seeing if you can cut down on strange ingredients/additives (anything you don't know what it is), or a few eliminations... BUT, some people imply you have to be so purist about it (1-3 months as a minimum excluding the suspect food) that I physically couldn't do it properly, not without locking said child up in a cupboard for that long.
How much processed food does he have at the moment?
Hi ragged, that is my concern really, that it will be a nightmare to get rid of all sugars. He eats very little processed food tbh. Most meals are cooked from fresh. He has a good appetite. He likes the odd pizza or burger (which kid doesn't) but meals at home tend to be chicken and rice, spag bol, lasagne, sundays roasts, jacket spuds. Quick teas tend to be beans on toast with cheese, fishfingers.
He does currently have sugary breakfast cereals - honey cheerios, coco pops and i think maybe this is where a change could be made to weetabix/cornflakes or wholemeal toast. After school he craves stodge - biscuits, choc filled crepes, crisps etc, this could be better.....