Seems like one of the major causes of American stupidity is their malnutrition.
Real food has made an enormous difference for me. In my case it's red meat, iodine, and vitamin D.
It takes time, though. They say it takes five years for a smoker's tar to clear from their lungs. Naturally this is optimistic. Plan on something more on the order of ten years. The effects of a bad diet last for a long, long time.
Fixing it is absolutely worth the wait.
P.S. I am starting to strongly suspect grains cause joint problems. Issue: this is a super prole thought. Grains cause grinding and starch causes dryness. Greasy meat causes good lubrication. No academic will admit anything can be even remotely as intuitive as that.