The suggestion that pcs subjects have compromised immune systems is more of a general statement that concussions can cause brain/gut axis infections. It is likely that head injuries cause inflammation which trigger viral or bacterial infections to replicate. This is not agreed upon yet, but logically makes sense and probably will be common knowledge in 100 years or so when doctors finally understand post head injury problems a lot more.

By brain fog, I mean slow thinking, inability to see clearly at long distances, inability to focus, inability to hold conversations with people due to trouble maintaining focus.

My doctor suggested 4000mcg of folic acid per day. Folic acid may be important for preventing birth defects or other physical problems, but for pure brain health I think methylfolate is far superior. People with PCS may have inflammatory conditions in their body that mess up the conversion process of folic acid to methylfolate.

Folic acid is not a natural chemical for humans. Folic acid is not present in a single food naturally. We eat food with folinic acid, which is then converted into its usable form methylfolate. So yeah, folic acid is not "natural" in any way.

I really just wanted to put it out there that there is no reason to take folic acid at all over folinic acid or methylfolate in my opinion.