alpha-tocopherol (α-tocopherol) is in

Vitamin E intake and risk of amyotrophic lateral sclerosis
Just a moment...

and is the only known substance showing statistically significant preventative affect of Amyotrophic Lateral Sclerosis, per above paper. The authors discovered individuals who took Vitamin E supplements reduced their risk of developing Amyotrophic Lateral Sclerosis more than fifty percent AFTER about ten years.

Several clinical studies tried detecting this effect but found no significant benefit in period (way too short to discover) . . . period was a couple of years.