Originally Posted by North
The fat soluble vitamins (A, D, E, &K) don't simply concentrate in the urine. They are distributed to body tissues and you definitely can overdose on them.
Yeah, you need to take care to watch your intake of the fat soluble vitamins. But even water soluble vitamins like B12, which are very easily flushed out of your system via urine should be watched as you are overworking your kidneys if they have to filter excess amounts of the stuff everyday over a long period of time.