L.C.
generally the human body is only able to absorb about 10-15% of over the counter vitamins because a lot of them are either a) loaded with fillers that block the bodies ability to absorb b) have conflicting vitamins and minerals that cross each other out c) it is an amount your body physically cannot handle at one time, etc.
i actually have a big file on vitamins and lack of them, etc. I would post it here, but i think it is too long? If you want it, please feel free to PM me. i would be happy to e-mail it on over to you. I work in health education and i am a bit of a nerd and love researching. lol. so i have just compiled some files for my own use. and dont worry, i dont sell anything. the info is all unbiased. lol.