by Obessian » Wed Mar 26, 2008 4:56 pm
The RDA was set to protect you from a vitamin deficiency back in the day when quality nutrition was not readily available. As far as I know.
So it's the MINIMUM threshold below which you're running a risk to your health. This means that everyone should try and consume vitamins in quantities ABOVE the RDA.
Now vitamins A and E (or D?) you can overdose on. It takes some effort to consume enough of the stuff to poison yourself, but with supplements it's possible. That's why the quantities of these vitamins in multi-vitamin supplements are usually limited. I.e. vitamin C tablets come in one gram doses (1000 mg), which is 1666% of RDA for vitamin C, but you'll rarely see vitamin A tablets at more than 75%-100%.
The other vitamins are deemed safe, as you just excrete (pee) whatever the body doesn't use. You can really see this with vitamin B complexes, as they turn your urine yellow and/or bright orange.