|
Examples of potential harm:
-Vitamin E can prolong bleeding time and has forced cancellation or delay of cancer surgeries; some studies suggest it may raise the risk of certain cancers.
-Beta carotene, a precursor of vitamin A, may raise smokers' risk of developing lung cancer.
-Folic acid supplements may raise the risk for precancerous growths in the colon.
-Vitamin C in large doses may help cancer cells resist chemo and radiation.
In January, doctors reported that a selenium supplement containing kelp -- which is loaded with iodine -- was interfering with the low-iodine care recommended for a man with thyroid cancer.
Herbals and dietary supplements can undermine cancer treatments in ways that patients can't feel and doctors can't measure. When a treatment fails, it's impossible to say whether it was due to the person's cancer or because a supplement subtly interfered.
"We know that there's some harm going on. We just don't know the magnitude of it," said Dr. Jeffrey White, the National Cancer Institute's complementary and alternative medicine chief.
Studies show that as many as two-thirds of cancer patients who use unproven remedies do not tell their doctors. Sometimes it is because they fear doctors will disapprove, but often it is because they do not realize it can harm their care.
"I didn't think they were medications. They're not prescription, they're not drugs. This is all natural substances, made from natural products," said Vince Palella, a Bradenton, Fla., prostate cancer patient.
During a nutrition counseling session, a Moffitt dietitian, Diane Riccardi, discovered that Palella was taking dozens of pills a day, including a saw palmetto extract. That supplement might have interfered with his hormonal cancer treatments or the monitoring to see if the those treatments were working.
"There's absolutely no way of knowing" if it did, Riccardi said. "The products he was taking were not highly purified -- they were a mishmash," including some labeled "raw herbal extracts," she said. Companies often claim their formulations are trade secrets and do not disclose all ingredients or amounts.
"It's as difficult as finding out what the recipe is for Coca-Cola" to try to decipher what's in them and whether they pose a risk, she said.
Another supplement that can pose a risk for prostate cancer patients is DHEA, which can affect testosterone levels, said Phyllis Matthews, a urology nurse practitioner at a group of Veterans Affairs clinics in the Denver area.
Cancer doctors also worry about isoflavones and other soy-related supplements; some research suggests they might stimulate breast tissue. Breast cancer patients on tamoxifen or aromatase inhibitors like Femara or Arimidex should not use red clover, dong quai or licorice because of estrogen-stimulating components, say guidelines from the Society for Integrative Oncology, a group of cancer experts that Cassileth heads.
Cancer survivors must be careful, too. Using a 2005 nationwide survey, Dr. Richard Lee of the University of Chicago found that half of survivors using supplements were at risk of problems because of other medicines they were taking.
He documented 116 potential interactions, including 9 percent that were major or possibly life-threatening. They included bleeding risks from combining ginkgo and aspirin, and heart rhythm, high blood pressure, and serious muscle problems from taking St. John's wort and Prozac or similar antidepressants.
Supplements also can be dangerous by themselves. Balducci, the cancer specialist at Moffitt, had a leukemia patient who was taking red yeast rice extract, which has been linked to a number of health concerns.
"It caused terrible damage to her liver" and prevented her from receiving chemotherapy for her cancer, which got worse and killed her, he said. Ironically, she was taking the supplement to boost her immune system -- a deceptive claim that has ensnared many cancer patients, including Palella, the prostate cancer patient.
"There are no herbal or vitamin supplements that we know of that will specifically boost the immune system," said Allen, the Moffitt dietitian.
White, at the National Cancer Institute, is angered by ads that tout test-tube results or that make scientific claims like "stimulates T cells" without any evidence that the same substance taken in pill form, or that the T-cell effect described, makes any difference in patients' survival.
"These kinds of leaps are just not acceptable. The purpose of that is to mislead people," he said.
Here, the government does have some authority. In June, the FDA sent 25 warning letters to sellers of teas, pills and other products sold on the Internet that falsely claim to cure, treat or prevent cancer.
The substances included bloodroot, shark cartilage, coral calcium, cesium, ellagic acid, cat's claw, Essiac tea and various mushrooms.
In September, the Federal Trade Commission charged five companies with making false and misleading claims for cancer cures and reached settlements with six others. The agency also started a bogus cures Web site to help consumers. A statement explained its reasoning:
"When you're battling cancer, the last thing you need is a scam."
___
On the Net:
Federal Trade Commission:
http://www.ftc.gov/opa/2008/09/boguscures.shtm
Food and Drug Administration:
Memorial Sloan-Kettering:
http://www.mskcc.org/aboutherbs/
Scam watchdog: http://www.quackwatch.org/
National Cancer Institute:
http://www.cancer.gov/cam/
Alternative medicine agency: http://nccam.nih.gov/
[Associated
Press;
Copyright 2009 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.
News | Sports | Business | Rural Review | Teaching & Learning | Home and Family | Tourism | Obituaries
Community |
Perspectives
|
Law & Courts |
Leisure Time
|
Spiritual Life |
Health & Fitness |
Teen Scene
Calendar
|
Letters to the Editor