Understand that I do NOT have ALS, I do have peripheral neuropathy, my children have a 3-PGDH deficiency. I have had no side effects from 25 mg per day (I weigh approx. 190 lbs), and I know others taking the same amount or more, with no obvious side effects. Others I personally know take it for nerve pain associated other disorders. I have been dealing with serine for about 20 years now.
I started taking it before there was research on it for neuropathy for various reasons. I know the concerns about the unknown, heck I almost had my mom sign papers before supplying her with some! But it worked for us, and now the research (out of Harvard University and Mass General Hospital) is catching up.
You can private message me and I can share some other links and information on Serine (from legitimate sources) if you like.