Have you ever popped a St. John's Wort tablet to feel perkier? Maybe you took milk thistle to soothe your liver after a big party?

People and some doctors recommend the treatments, but they can cause problems.

"We had a patient in clinic taking a lot of homeopathic Prozac, and when we looked it up, one of ingredients was strychnine," said dietitian Roberta Anding, director of sports nutrition at Texas Children's Hospital.

Millions try supplements each year as an alternative to prescriptions or in addition to treatment. It's a $1.9 billion business in the U.S., according to The Nutrition Business Journal.

How much do you really know about your supplements?

'All-Natural' Doesn't Equal Safe

Anding said terms on the label like "made from plants," "natural" or "herbal" give some a false sense of security.

"I think often American consumers are so wanting to trust that a vitamin, herb or homeopathic treatment could only be for the good that they don't realize that the word natural means nothing. I challenge people to think, what if this was an 'all-natural' birth control pill -- you wouldn't take that in a million years. Tobacco, cocaine -- those are plant-based, too," Anding said.

Educated Consumers

Getting educated on what's in a supplement before you take it poses a challenge. The Food and Drug Administration doesn't test supplements before they hit the store shelves. The government can recall supplements if a problem is identified, but that happens rarely, Anding said.

There are two problems: the full ingredient list may not be readily available or may not be written in plain English; or the science may conflict about a particular product's efficacy.

Science Can Be Shell Game

For instance, one set of research showed vitamin E helps the heart, but it has been denigrated recently after further research found that taking too much can dangerously thin the blood.

"One study gave half a teaspoon a day of cinnamon to diabetics, and people taking the cinnamon had lower blood sugar," said Alegent Health dietitian Toni Kuehneman. "The supplements industry started producing cinnamon pills, but pills aren't tested. It was the ground cinnamon tested. The industry takes a shred of evidence and then sell the pills."

Ingredients May Hide From Label

Consumer Reports said that from "January through September 2007, the U.S. Food and Drug Administration issued nine 'safety alerts' warning consumers to stop using 13 brands marketed as dietary supplements because FDA testing found they contained prescription medications."

Consumer Lab reported that "more than 30 percent of multivitamins tested contained significantly more or less of an ingredient than claimed, or were contaminated with lead."

Enter the National Center for Complementary and Alternative Medicine at the National Institutes of Health. It was created in 1998 to research complementary and alternative healing practices.

But the sponsor of the bill that created NCCAM, Sen. Tom Harkin, D-Iowa, said this year that NCCAM wasn't working as he'd intended -- it was turning down too many alternative therapies.

"One of the purposes of this center was to investigate and validate alternative approaches. Quite frankly, I must say publicly that it has fallen short," Harkin said.

Harkin is said to be thinking about cutting funding for NCCAM.

Help Does Exist

There are plenty of worthwhile supplements, the dietitians said. So where can you look for good advice?

"There are free Web sites that monitor over-the-counter supplements. My favorite is QuackWatch.com," said Kuehneman.

"I subscribe to ConsumerLabs.com," said Anding. "They send e-mail alerts for recalls, they analyze and compare pills -- it's worth it if someone is really wanting to take care of their health with supplements."

Also, look for red flags on the label.

"I tell people that if the label gives you things you don’t understand, or asks you to consult a doctor, it may not be the safest approach for long-term results," said Omaha, Neb., Hy-Vee grocery store dietitian Carrie Nielsen. "A pill can’t take the place of a healthy, balanced diet."

Anding chooses brand names over unknown companies and advises patients to ask their pharmacist.

"Go out and be cynical. If you're at the store, ask for info on latest recalls," Anding said.

In particular, supplements that Anding, Kuehneman and Nielsen promote for certain patients are folic acid, vitamin D, fish oil and calcium. They'd prefer people get them from food, but pills will do.