Updated: 01/29/2014 4:44 PM
Created: 01/29/2014 4:42 PM WDIO.com
By: LAURAN NEERGAARD, AP Medical Writer
WASHINGTON (AP) - Antioxidant vitamins are widely assumed to be cancer fighters even though research in smokers has found high doses may actually raise their risk of tumors. Now a new study may help explain the paradox.
Swedish scientists gave antioxidants to mice that had early-stage lung cancer, and watched the tumors multiply and become aggressive enough that the animals died twice as fast as untreated mice.
The reason: The extra vitamins apparently blocked one of the body's key cancer-fighting mechanisms, the researchers reported Wednesday.
The scientists stressed that they can't make general health recommendations based on studies in mice, but said their work backs up existing cautions about antioxidant use.
"You can walk around with an undiagnosed lung tumor for a long time," said study co-author Martin Bergo of the University of Gothenburg. For someone at high risk, such as a former smoker, taking extra antioxidants "could speed up the growth of that tumor."
Antioxidants are compounds that help protect cells from certain types of damage, and antioxidant-rich fruits and vegetables certainly are healthy. The question is the health effect of extra-high doses in pill form. Studies in people have shown mixed results but haven't proven that vitamin supplements prevent cancer, and a few have suggested the possibility of harm. One study in the 1990s found beta-carotene increased the risk of lung cancer in smokers. Nor are smokers the only concern: A 2011 study found Vitamin E supplements increased men's risk of prostate cancer.
As for people who already have cancer, the National Cancer Institute says: "Until more is known about the effects of antioxidant supplements in cancer patients, these supplements should be used with caution."
But biologically, scientists couldn't explain why antioxidants might harm. Wednesday's report in the journal Science Translational Medicine is a first step to do so.
The research doesn't examine whether antioxidants might help prevent tumors from forming in the first place - only what happens if cancer already has begun.
The researchers gave Vitamin E, in a range of supplement doses, or an antioxidant drug named N-acetylcysteine to mice engineered to have lung cancer.
The antioxidants did prevent some cell damage. But doing so prevented a well-known tumor-suppressing gene named p53 from getting the signal to do its job, explained study co-author and Gothenburg biologist Per Lindahl.
The antioxidants "allow the cancer cells to escape their own defense system," he said.
(Copyright 2014 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.)
Four Residents Escape Lincoln Park Apartment Engulfed in Flames
A home in the Lincoln Park neighborhood was enveloped by flames early Wednesday morning. All four people were able to leave the apartment complex safely. Our crew arrived around 5:00 a.m. at the 2700 block of West 4th Street in Duluth.
Judge Denies Mistrial in Little Falls Shootings
A Minnesota judge has denied another request for a mistrial in the case of a homeowner who killed two teens who entered his home.
Minn. Senate Backs New Cell Phone Tracking Rules
New restrictions on police use of cell phone tracking technology have won backing from the Minnesota Senate.
Minn. Lawmakers Wrestle with Privacy Protection
Minnesota lawmakers are wrestling with ways to prevent public employees from abusing access to citizen data.
Superior Murder Trial Delayed after New Evidence Released
Juan Leonardo Padilla, 40, of Fort Mohave, Ariz., is charged with the shooting death of 46-year-old Terrance Rodney Luukkonen of Duluth last May. Luukkonen was shot outside his workplace at Genesis Attachments in Superior.