MTHFR and vitamin B12 deficiency: Vitamin B12 deficiency and MS share pathological changes and B12-dependent methylation and MTHFR have been suspected to play a role in MS for decades.32 Homocysteine levels in the blood and cerebrospinal fluid of MS patients have been found to be elevated in some studies,33–35 but not in others.36, 37 A recent study found different concentrations of methionine metabolites in brains of MS patients compared to brains of controls and suggested an effect on mitochondria and neuronal energetics.38