Dr. Grossberg ticks off other common herbs that people take without realizing their side effects or how they might interact with medications.
St. John's wort sometimes is taken for anxiety and depression. Those who also are taking antidepressants or anti-anxiety medications, such as Prozac, Zoloft or Paxil, should beware. Mixing St. John's wort with these medicines can cause serotonin syndrome -- with symptoms that may include agitation, rapid heart beat, flushing and heavy sweating -- that may be fatal.
Dong quai, which some women take for menstrual disorders and to ease symptoms of menopause, has been linked to cardiovascular problems, such as irregular heart rhythm and low blood pressure. If a patient takes the herb along with an antihypertensive drug, her blood pressure could plummet, putting her at risk of stroke.
Some people take echinacea, which enhances the immune system, for the common cold. However, those who also take Lipitor, Celebrex and Aleve face an increased risk of liver damage. Echinacea also can be harmful for those who have multiple sclerosis, diabetes, HIV infections or allergies.
Dr. Grossberg and his co-author Barry Fox make it clear that they're not anti-herb or anti-medicine.
"There just are a lot of things people can take that have a lot of bad interactions. And on some level it makes sense for them to think that what they're doing is safe. They associate natural remedies with nature and think if the supplement wasn't safe, they couldn't pick it up without a prescription.
"Hopefully this will get them to think more about it so they look before they leap. People can look up what they're thinking of taking and see if there's efficacy. And they should always talk to their doctor about everything they're taking."