Numerous studies have shown that antioxidants may halt cancer progression. But a new study from researchers at the Sahlgrenska Academy at the University of Gothenburg in Sweden has found that antioxidants may actually speed up the progression of lung cancer.
The findings are published in the journal Science Translational Medicine.
Antioxidants are chemicals that are present in some pharmaceuticals, foods and nutritional supplements.
In the body, antioxidants interact with free radicals and neutralize them. Free radicals are chemicals that can potentially harm cells.
Although they form naturally in the body and play a role in many normal cellular processes, free radicals can damage cell components - such as DNA, proteins and cell membranes - at high concentrations. This process may contribute to the development of cancer.
Laboratory and animal studies have suggested that antioxidants are able to prevent types of free radical damage associated with cancer development.
But in this new study, led by Prof. Martin Bergo of the Sahlgrenska Cancer Center at the University of Gothenburg, the findings suggest otherwise.
Antioxidants 'deactivate p53 protein to cause tumor progression'
Contrary to previous studies, new research suggests a diet with added antioxidants may actually speed up lung cancer progression.
One group of mice received additional antioxidants in their diet in the form of vitamin E and acetylcysteine - two of the most commonly used antioxidants. These were given at levels equivalent to what a human would get from ordinary multivitamins.
The second group received no additional antioxidants in their diet.
The researchers found that the mice who received extra antioxidants in their diet had three times as many tumors and died twice as fast as the mice that had no additional antioxidants.
Furthermore, the mice who received additional antioxidants had bigger tumors than the control mice.
The investigators then confirmed their findings using human lung cancer cells.
Explaining the mechanisms behind tumor progression from antioxidants, Prof. Bergo says:
"When the antioxidants attack reactive oxygen radicals in the tumors, a protein called p53 is deactivated. [This protein] has a neutralizing effect on tumors, and when it's gone the tumors can grow faster and more aggressively."
Implications for patients with chronic lung disease
The researchers note that acetylcysteine is an antioxidant commonly used by patients who have chronic obstructive pulmonary disease (COPD), as it is able to dissolve mucus.
Prof. Bergo says their findings may have important implications for this patient group.
"Many COPD patients have been smokers and therefore have a higher risk of lung cancer. It is too early to give recommendations regarding the use of acetylcysteine in COPD patients, but our study clearly points to a need for new research on this topic," he says.
However, Prof. Per Lindahl, of the Sahlgrenska Academy and co-author of the study, notes that people should not stop taking antioxidants based on the team's findings.
He stresses that the study does not analyze the risk of developing cancer, but looks at how antioxidants may speed up progression of cancer that is already there.
Prof. Lindahl adds:
"For people who already have a small lung tumor but don't know it, there is a risk that antioxidants may speed up the progression to cancer.
Consequently, people in obvious risk groups, such as smokers, may consider not taking extra antioxidants, but we still have no scientific support for such a general recommendation."
The research team plans to carry out further research to determine how antioxidants affect other types of cancer. They also want to see whether antioxidants contribute to the development of cancer in healthy mice.
Last year, Medical News Today reported on a study suggesting that resveratrol - an antioxidant found in red grapes - may counteract the benefits of cardiovascular exercise.