Evidence suggests that HFCS is linked to a plethora of health issues and bodily dysfunctions. However what is not often talked about is the fact that it also seems to lower IQ.
https://www.mitchmarderdds.com/blog/eating-sugar-drastically-lowers-your-iq/
https://patch.com/new-jersey/ramsey-nj/can-eating-su
https://www.livescience.com/20329-s

Anyone familiar with the USA will tell you, high fructose corn syrup shows up in unexpected places due to lobbyists and corn subsidies, and without intense diligence and caution, it is difficult to entirely avoid it. It tends to sneak into the diet in places like bread, sports drinks, any processed food, coffee sweeteners, prepackaged foods, and so on.

It is likely that if you grew up in the US, you have been exposed to harmful amounts of HFCS throughout your life.

How can these damages be reversed? Is it permanent?

What are some other foods/chemicals that are linked to cognitive decline, and how can one avoid them/mitigate the damage? I know fried foods and some types of refined oils are also linked with cognitive damage and gut biome disruption. Anything else?

I have seen that a small handful of studies (or perhaps the same study being referenced multiple times) seemed to indicate DHA/Omega-3 with potential protection or reversal of the cognitive damages associated with HFCS consumption, but everything I have been able to find online implies that these studies were very short term and the results were not conclusive or repeated. Has there been any long term research on this? If so, where can one read about the results?