[lee b]

i have this person who is trying to sell me this supplement. I noticed the b vitamins are listed at 1667% of rda. Should I be concerned ?

[mrsD]

Depends on which vitamin it is. B12 will show a high % over RDA because B12 is not well absorbed orally, so is provided in higher doses in order to squeek a few micrograms thru the intestines. Most mixtures don't have ENOUGH B12 in them for this in fact.

But if it is B6 that high percentage is very troubling.

What really matters is the manufacturer and the whole listing of ingredients.

[Dr. Smith]

RDA is only part of the story. Here is an article explaining the histories of the RDA (Recommended Daily Allowance) and how it became DRI (Dietary Reference Intake), as well as other values it gave rise to, i.e. EAR (Estimated Average Requirement), AI (Adequate Intake), and UL (Tolerable Upper Limit)—which for some vitamins & nutrients, including B12, has not been determined.

It's that last one—the UL (Tolerable Upper Limit)—that we should be concerned about with regard to too much of this or that.

Nutrient Requirements Get a Makeover:
The Evolution of the Recommended Dietary Allowances

See also: tolerable upper limits of vitamins and minerals

Doc