Its clear most have lost sight of the notion that many of the vitamins are catalysts, and should only be ingested in catalytic amounts. One example is riboflavin B2. According to one study I saw, their male subjects would void in their urine any amount of B2 they ingested over 1.7 milligrams. Yet, in the vitamine shops, the B2 pills are all like... 100 milligrams. Like, each 100 mg pill is actually 60 days worth.... This same concept applies to many other vitamines, and substances in general. This includes B-12, where a response is seen when it is present only in one part-per-billion levels.
Yet, I see people getting B-12 "shots"..... An easy way for me to take thiamine, B1, I sprinkle a few milligrams into my coffee, just a tiny amount. Consider this last example.... something called PQQ, pyrroloquinoline quinone. This substance is shown to regeenerate mitochondria and stimulate formation of new mitochondria ! Yet, if you buy a pill of it, it is 50 milligrams or some grotesque figure like that. Upon further inspection, we find, the foods highest in PQQ to be kiwi fruits and celery. It turns out, if you were absolutely starving and had to pig out on kiwi and celery, by the time you felt full, you'd have only ingested one one-hundredth of a millligram of PQQ. The point being, this is the max amount one would expect to EVER get from Nature. My only explanation of why anyone would take 50mg of it, is that they're ignorant of the way that too much of a "good thing", can have an opposite effect of that which is desired. Some vitamins like the ascorbate complex, you can take as much as you want. Others, in my humble opinion, are easily abused by taking too much, because most people think along the lines of "if a little is good, then more is better". Tread lightly, look before you leap, etc.