The Benefits of Macronutrients in People Living with ALS: What Should We Eat?
The Benefits of Macronutrients in People Living with ALS: What Should We Eat? | NEALS

One of the very few things associated with decreased risk of incurring Amyotrophic Lateral Sclerosis is vitamin e, per this journal report based on the American Cancer Society's Cancer Prevention Study II. Their study involved nearly one million patients, about 500 would develop Amyotrophic Lateral Sclerosis, which is discussed in this study:

Vitamin E intake and risk of amyotrophic lateral sclerosis
Vitamin E intake and risk of amyotrophic lateral sclerosis - PubMed

Subsequent studies have tried to test post onset benefits from this vitamin and also vitamin c but found no statistically significant results. They might be too short in duration to detect the benefit.

Familial candidates especially ought to note the vitamin e link.