Use of the B vitamins, particularly folic acid and methylcombalamin, have been largely driven by the observation that patients with ALS may have elevated plasma homocysteine levels. In the transgenic SOD-1 mouse model similar elevation of plasma homocysteine was found. Vitamin B12 and folate are involved in reactions that convert homocysteine to methionine, thereby potentially reducing homocysteine levels. Furthermore, vitamin B6 functions in an alternative pathway to convert homocysteine to sulfur amino acids. 
Discussion threads on the ALSTDI forum
- Rosenfeld & Ellis: Nutrition and dietary supplements in motor neuron disease. Phys Med Rehabil Clin N Am 2008;19:573-89, x. PMID: 18625417. DOI. Compromised nutrition leading to weight loss is a common and significant problem in the amyotrophic lateral sclerosis (ALS) patient population. The benefit of aggressive and early nutritional therapy can profoundly influence the disease course, quality of life, and survival. This article reviews the role of nutrition, both as sustenance and treatment for patients who have ALS. Self-medication with dietary supplements has become increasingly popular within this patient population. Despite their popularity, the efficacy of these compounds has been largely unsupported by formal clinical trials. Available data will be highlighted to provide a basis upon which to advise patients requesting guidance.