Sarah, Milk Thistle is one of the very few herbs that doesn't have any real side effects or other contraindications (none I'm aware of anyway). And unlike so many of the other popular herbs, I haven't read any claims against long term use. It's been said to have a possible slight laxative effect in some but not most people. Harry is right in suggesting buying from a reputable company. Over the years, Nature's Way has gained my trust as the best and Solaray is probably a close second (this is my opinion). I would stay away from specific brands you only find for example in K Mart or Wal Mart. I agree there should be better standards for the industry. With many herbs, you often don't know the potency, however there is "standardization". You know you're taking a strong enough product and just how strong it is. The only problem is that there are some companies out there that don't give you what's on their label. This is the exception and not the rule. I do NOT believe the FDA should be the ones in charge of a better regulation process. That would be the first step in getting them removed from the shelves. As you know, the FDA is very much on the side of the drug companies who see the alternative medicine industry as a threat to their business. I don't have much trust in the FDA anyway because they've often been to quick to approve medicines and food additives which are clearly dangerous. Two perfect examples are Prozac and Aspertame. How these products are still allowed on the market is beyond me!