About six weeks ago, just for kicks, I bought a bottle of adenosylcobalamin which is one of the co-enzyme forms of vitamin B12 (the other one being methylcobalamin). I have previously bought methylcobalamin and experimented with it (finding no effects). But in my 25 years of being vegan, I had never tried adenosylcobalamin. So for the last six weeks, I’ve been taking 3,000 µg per day on most days. If I have experienced any health changes from them, I haven’t noticed it.
But during this time, I have also been corresponding with someone who has been struggling with fatigue on a vegan diet and he claims that adenosylcobalamin has been helping him. I checked out some of the links he provided of other people who claim the same thing and added this paragraph to Alternatives to Cyanocobalamin: Methylcobalamin & Adenosylcobalamin:
“I am unaware of any clinical trials testing the various forms of vitamin B12 against each other among the general population and most people seem to do well using cyanocobalamin. But some people with chronic fatigue report getting more relief from adenosylcobalamin than either methylcobalamin or cyanocobalamin (more info), while other people report feeling better only when taking both co-enzyme forms (adenosyl- and methyl-).”
I am not necessarily convinced that adenosylcobalamin was the reason for any of these people’s improvements as they are typically trying other things as well and there is also the placebo effect to consider, but the claim has become common enough that until more research is done, it is worth considering.