Lead pollution via cars and paint seems another one that I thought was fairly well supported.

Also Iodine-deficiency, though not sure that's covered by nutrition since it's now added to salt.

People seem very attached to the "you can't do anything" approach though. I find it hard to imagine what a society without education would look like though, even if the people all had high IQs, so presumably there's some benefit to passing knowledge onto the next generation?