An excerpt on B12... and WHY sublingual, and WHY methylcobalamin...
"For years, B12 shots have been an unofficial treatment for fatigued, run down, or depressed patients. (Large oral doses are very poorly absorbed, though sublingual and intranasal B12 formulations appear to give injections a run for their money.) The practice has been the butt (pun intended) of many jokes among skeptics. Yet what research there is has supported it.
In 1973, in a double-blind trial by F. R. Ellis and S. Nasser, B12 shots boosted the energy and lifted the moods of chronically fatigued patients significantly more than shots of water. Sixteen years later, in a less formal single-blind study, orthomolecular psychiatrist Herbert Newbold reported that his B12-responsive patients "invariably" were able to tell whether they had received B12 or an injection of water. Newbold also noted that B12 is not a simple stimulant, but a "normalizer" that helps some of his patients sleep better and even made one less manic. (Mania is a symptom of B12 deficiency.)
Newbold's suggestion that B12 is a mood stabilizer is echoed by recent research in which oral megadoses of methylcobalamin – the most bioactive form of B12 – has shown promise as a regulator of disturbed sleep-wake rhythms. Methylcobalamin has been particularly well-studied in Japan as a treatment for delayed sleep phase syndrome; that is, not being able to fall asleep until very late at night and needing to sleep in every morning. Because sleep-wake disturbances are part and parcel of most mood disorders, B12's apparent sleep-wake regulatory effect could help account for its mood-stabilizing benefits. In a 1996 study by G. Mayer et al., three grams a day of methylcobalamin, but not cyanocobalamin (the form of B12 in most supplements), managed to decrease sleep time yet improve sleep quality and daytime alertness in a small group of healthy men and women.
There is an intriguing reason why some people with normal blood levels of B12 may need megadoses of the vitamin. They may have a B12 deficiency that is confined to the brain.
While most doctors would never consider such a possibility, studies have documented local cerebral deficiencies of B12 (using cerebrospinal fluid levels as a measure) in people with Alzheimer's disease, postpartum depression, and toxic neuropsychiatric disorders, including toxic depression."