Antioxidants have been long thought of as having a protective effect against cancerous tumors. Much to their surprise, Swedish researchers have found evidence that the opposite is true for some people.
University of Gothenburg professors Martin Bergö, Ph.D.,a researcher at the Sahlgrenska Cancer Center, and Per Lindahl, PhD., a visiting professor, said in an interview that supplementing the diet with the antioxidants N-acetylcysteine (NAC) or vitamin E, can “markedly increase tumor growth and reduced survival by half” in people who have precancerous lung cancer lesions or existing lung cancer.
The paper, "Antioxidants Accelerate Lung Cancer Progression in Mice" was published in the Jan. 29, 2014 issue of Science Translational Medicine, a journal of the American Association for the Advancement of Science. Bergö and Lindahl are the paper’s co-corresponding authors.
The concept that antioxidants can help fight cancer is deeply rooted in the general population and is promoted by the food supplement industry, the paper said. Some scientific studies support this finding.
Researchers chose to study what effect the two antioxidants had on lung cancer because it is the most common form of cancer, aside from skin cancer. Their discovery however came about in an unexpected way.
The research, led by Dr. V.I. Sayin at the University of Gothenburg, used mouse models with lung cancer cells as a control experiment as part of another study. In that study, one group of mice was treated with antioxidants and one group received no treatment.
“We really expected to get a protective effect," Lindahl said referring to the group treated with antioxidants. "When we evaluated the results, to our surprise we saw lung cancer tumors had increased in the treated group by threefold. That prompted us to conduct another study.”
While translating results from animal studies to humans should be done with caution, Lindahl said in this current study, “there are strong arguments that suggest the results may be relevant.”
He pointed to the lung cancer in the animal model. “These are very similar to those that develop in humans, and it’s likely they develop in mice and humans by similar or identical mechanisms,” he said. Additionally, the team has conducted identical research on human lung cancer cell lines where they obtained the same results.
The researchers said that the study raises a lot of important questions.
For starters, do other cancer types respond to antioxidants the same way lung cancers do, with accelerating growth and proliferation? The team is currently studying melanomas, leukemias and gastrointestinal tumors in an attempt to answer this question.
Another key question is this: Are patients with chronic obstructive pulmonary disease (COPD), a condition often associated with tobacco smoking, at an increase risk of developing tumors too?
COPD patients are often prescribed large amounts of Acetylcysteine, a potent antioxidant, to relieve mucous production. Bergö believes it's highly probable that an increased risk exists for COPD patients and they should be evaluated.
In the meantime should people stop taking antioxidants? Bergö says yes. He thinks it’s a good idea for people at risk of developing lung cancer or those who’ve already been diagnosed.
“It’s important to note that our study doesn’t say anything about antioxidant use in healthy people and their future risk of developing lung cancer. What we’re showing is in people with an increased risk of lung cancer or if you already have a small tumor, then antioxidants might be dangerous.”
Lynette Summerill is an award-winning writer and watersports junkie who lives in San Diego with her husband and two beach loving dogs. In addition to writing about cancer-related issues for EmpowHER, her work has been seen in publications internationally.
Sources:
Interview with Martin Bergö and Per Lindahl. Elin Lindström Claessen. Video of interview online at:
http://www.eurekalert.org/multimedia/pub/67940.php
Antioxidants Accelerate Lung Cancer Progression in Mice. V. I. Sayin, M. X. Ibrahim, E. Larsson, J. A. Nilsson, P. Lindahl, M. O. Bergo, Antioxidants Accelerate Lung Cancer Progression in Mice. Sci. Transl. Med. 6, 221ra15 (2014).
http://stm.sciencemag.org/content/6/221/221ra15
Reviewed February 25, 2014
by Michele Blacksberg RN
Edited by Jody Smith