I take sublingual nuggets of methylcobalamin (1000mg ? I can't reproduce the upside down "h" symbol on the bottle - I think it stands for micrograms). One a day, and they definitely make enough of a difference that I will not be without them in future. Dirt cheap, and as cost is always a factor, if nto the deciding factor, for me, I consider these well worth it.
Usually winter for me is a total write-off due to fatigue and an increase in CD symptoms, not to mention SAD; and of course during flare-ups in summertime, there is not a lot of difference. Since I started taking the B12 I have noticed a much decreased variability in symptoms of all sorts; although it does nothing for the SAD the simple fact that I have more energy and am more lucid with a better memory (the latter admittedly may be more to do with B5 that I take) makes an enormous change in my ability to manage everyday tasks.
I am convinced that B12 in biological terms in humans, is what the military would call a "force multiplier" (like an AWACS aircraft that co-ordinates air or ground support). It is used as a catalyst in numerous reactions within the body which also utilise other nutrients; if you do not have these other nutrients, taking a B12 supplement will not help. If you take a B12 supplement and it does nothing to improve your symptoms, look at other deficiencies as a cause for your problems.
But where you do have these other nutrients, constantly
having enough B12 in the body to use them, multiplies the potential benefits and will help even out dips and troughs in energy levels/cell nutrition quality.
The spray works on the basis that spraying the B12 through the nasal membranes puts it into the bloodstream; non-sublingual, oral pills will not work as the gut needs an "intrinsic factor" to enable absorption, and damaged guts lack this. Even the sublingual nuggets, from what I hear, have a "co-enzyme" to help absorption; to be honest, the whole intrinsic factor is so complex I am confused by it, it is the sort of thing that makes my head spin. But the main things you need to know are that it is not enough to put straight B12 into a damaged gut because it can't be used as it is, and B12 can be stored in the liver for considerable periods of time for use when needed. (But I don't know how effective this mechanism is; if you need to use glycogen from the liver, there is a considerable time lag before it starts to break down, compared to alternative energy use pathways.)
Rob, lots of dreams in technicolour are a rule of thumb sign for dietitians that you have enough B6; if you lack B6 you don't remember dreams, and tend to dream in black and white ! The "mind's eye" uses a lot of B6 for visualisation, it seems.
Isn't life weird...