Millions of people take vitamins, minerals and herbal pills every day, hoping to stay healthy, and avoid disease. Much of that money is spent on antioxidants, like vitamins C and E, which is commonly believed to prevent or delay some types of cell damage, such as cancer. But new research suggests that taking high levels of the supplements may actually be increasing the risk by knocking out the body's natural defenses against cancer.
Antioxidants are chemicals naturally produced by the body, or provided by fruits and vegetables, that neutralize what are known as free radicals, harmful molecules that accumulate inside cells and damage DNA. Without antioxidants, cells turn cancerous.
But despite dozens of studies, there’s never been any evidence that taking extra antioxidants, in the form of pills, prevents cancer, said Martin Bergo, a professor of molecular medicine at the University of Gothenburg. In fact, in an interview via Skype, he said excessive doses of the supplements could be harmful.
“But this thing is deeply rooted in the belief of people because [of] these free radicals that form inside the cells,” he said.
Bergo said dozens of studies have shown little or no benefit from taking antioxidants. He said other trials had to be halted because researchers observed an increased cancer risk.
in the journal Science Translational Medicine
described how two research teams, one led by Bergo and another overseen by cancer researcher Par Lindahl, discovered by accident that high doses of two antioxidants - vitamin E and NAC (N-acetyl-cysteine) - fueled lung cancer in mice.
Lindahl, also of the University of Gothenburg, said researchers were looking at how a particular protein that binds to DNA might contribute to lung cancer.
In a Skype interview, Lindahl said all of the mice in the study had small lung tumors. To create a control group, the researchers gave some of the rodents antioxidants, expecting that to limit their tumor growth.
“And it turns out that mice that were treated with extra antioxidants, they developed larger tumors compared to untreated mice. The tumors looked more aggressive, and the mice died twice as fast as the untreated mice," said Lindahl.
Researchers found high antioxidant levels reduced the activity of P-53, a protein that normally limits cell damage and prevents cancer. While more studies are needed before any recommendations for humans can be made, the researchers suggest that people with small, undiagnosed lung tumors could potentially fuel cancer by taking antioxidant supplements.
A spokesman for the American Cancer Society
called the study’s results “intriguing” but agreed it is too early to draw any conclusions.