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When Supplements Become Dangerous

They're not as harmless as you may think

A year after undergoing a kidney transplant, the 74-year-old patient was doing remarkably well. But when doctors reviewed his blood tests, they discovered an alarming mystery: Levels of the drug that was preventing the patient’s body from rejecting the transplanted kidney had dropped significantly. “We had no idea why at first,” says Joseph Boullata, associate professor of pharmacology and therapeutics at the University of Pennsylvania School of Nursing.

See also: Slideshow of 10 supplements that can interfere with your prescription meds — ginseng, kava, licorice and more.

Aloe Vera Americans spend millions on supplements that don't work and supplements that can actually harm them.

When taken orally, aloe vera may interact with medicine used to treat diabetes. — Photo by Reneé Comet

It wasn’t until the hospital pharmacist talked to the man’s daughter that they found the explanation. The patient had begun taking a dietary supplement that included Saint John’s wort, which is marketed to improve mood. “No one had mentioned it because no one really thought of it as a medicine,” says Boullata. But Saint John’s wort can speed the breakdown of some prescription medicines by eliminating them from the body before they can take full effect. If the blood test hadn’t alerted doctors, the supplement might have triggered rejection of the kidney — or even death.

Today, half of all Americans take dietary supplements, according to the National Institutes of Health’s Office of Dietary Supplements. Consumers spend more than $28 billion a year on vitamins, minerals and herbal remedies, in hopes that they’ll cure everything from insomnia to depression. And because many dietary supplements are touted as “natural” and are often sold in health food stores, it’s easy to assume they’re harmless.

While supplements can be harmful at any age, men and women age 50 and older are more likely to encounter problems. First, older people more often have chronic conditions like kidney or liver disease, which make it harder for the body to process compounds found in supplements. Then, too, they usually take more prescription drugs than younger people — and the more medications you take, the greater the risk of hazardous interactions with supplements.

The Food and Drug Administration regulates dietary supplements but does not apply the same rules it uses for medications. Manufacturers are not required to obtain approval from the FDA before marketing supplements. Under federal law, manufacturers are responsible for making sure their supplements are safe, and the FDA steps in only when troubles arise. Unfortunately, adverse interactions with prescription drugs may go undetected for a long time, even by physicians.

Disturbing trend

According to recent survey by the AARP Public Policy Institute, 59 percent of people 50 and older had used supplements in the previous month, and 52 percent took them daily. Fewer than half said they talked to their doctors about the pills they took.

“It’s a serious problem, and getting more serious as the number of medications and herbal products increases,” says K. Simon Yeung, a pharmacist and herbalist at Memorial Sloan-Kettering Cancer Center, where he manages a database of supplement information available to physicians and patients. According to Yeung, about 50 percent of cancer patients use some kind of dietary supplement to ease symptoms or side effects — or, out of desperation, in search of a cure.

Yeung is convinced some herbs help alleviate their symptoms. Unfortunately, several popular herbal supplements pose risks for people with cancer. Saint John’s wort, the same herb that washes antirejection drugs out of the body, can also speed the breakdown of certain cancer chemotherapies, robbing them of cancer-killing potency. And vitamin C, in megadoses, can interfere with the effectiveness of cancer drugs.

Next: Have blood clots? Beware of garlic supplements. »

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Although supplements may be labeled as "natural," that doesn't mean there aren't any risks associated with taking them.

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