This does seem to happen in medicine and nutrition, things that start on the fringe sometimes move to the mainstream. I thought my lunatic ex was out of his mind when he said fasting could heal disease, but it turns out it can, just not in the universal magical way he thought.
DO whatever makes you feel better is not bad advice. Some of these studies have overarching trends that I do believe - caffeine and Adderall are protective to your brain, a little bit of speed keeps the brain healthy.
Alcohol and Benadryl are risky over time, so a habit of downers is detrimental to the brain over time.
Logically this makes sense. I think to some extent it’s just metabolism/weight, staying lean is healthier all round but there does seem to be a pattern of results showing a habit of doing a little bit of stimulants is good for you.