Herbal supplements are not regulated all that well by the FDA, so when you buy some there is not guarantee whats in them or what medical effect they will have on you.

A Canadian lab analyzed 44 bottles of popular herbal supplements and found most were diluted with weeds, powdered rice, and wheat.  Some were just rice and weeds.

No brand names were revealed of the 44 bottles but Americans spend about $5 billion a year on herbal supplements.