From here : http://findarticles.com/p/articles/mi_m0FKA/is_n6_v58/ai_18356464/ "The activity of the autonomic nervous system is influenced by the amount of neurotransmitters (the fuels that run it). In studies by Jerold Morantz, D.C. and Walter H. Schmitt, Jr., D.C., one of which appeared in Compiled Notes on Clinical Nutrition (1990), have shown that the pH (acid-base balance) of tissues, and the ratio between certain B vitamins (thiamin and riboflavin), both influence this activity. Parasympathetic activity (near vision) is increased by: its neurotransmitter, acetylcholine; a relatively alkaline tissue pH, which makes the appropriate cells more responsive to parasympathetic stimulation; and by supplementation with riboflavin. Sympathetic activity (far vision) is increased by: its neurotransmitter, norepinephrine; a relatively acidic tissue pH which makes it more responsive to sympathetic stimulation; and by supplementation with thiamin, which promotes sympathetic activity." Food for thought.