No, this is by no means an excuse to stop eating berries and beans and apples and all the other healthy foods high in antioxidants, those natural chemical compounds — the most famous are vitamins A, C and E — that help protect cells from damage. If there's one thing scientists agree on, its that plant-based foods are good for us.
But antioxidant supplements or drugs, in people at high risk for lung cancer, may not be. A new study just out in the journal Science Translational Medicine suggests that antioxidants in mice with incipient lung tumors can dramatically boost the risks of cancer, tripling the number of tumors and speeding death. And the researchers say they've figured out how this works: The antioxidants seem to lower levels of a key suppressor of tumors, a protein called p53. From the press release:
Studying two different antioxidants, vitamin E and a drug called acetylcysteine, Martin Bergö and colleagues found that antioxidants sped up the progression of lung cancer in mice and in human cell lines. The authors used normal daily dietary doses of vitamin E and relatively low doses of acetylcysteine (humans typically received the antioxidant in an inhaled form, but the mice received it by mouth). When mice with early stages of lung cancer were given antioxidants, their tumors accelerated in growth, became more invasive, and killed the mice twice as fast compared to mice with early lung tumors that didn’t receive antioxidants.
So what are we to make of this? Oftentimes, basic scientists like Bergö, of the University of Gothenberg, in Sweden, punt on such questions. It's not their job to translate bench work to the bedside. But Bergö answered the question head-on during a press conference.
"If I had a patient with lung cancer, I would probably recommend that they do not take extra antioxidants," he said. "Would I make a general recommendation to healthy patients? Definitely not, because we haven't studied that and we don't have any data on that."
What would he say to a patient with chronic lung disease who was taking the antioxidant drug acetylcysteine to improve breathing? "I don't know what I would say, actually. I would make sure that as much research as possible is sparked from this as soon as possible, to determine if acetylcysteine use in this patient is causing an increased risk of cancer."
Let's add a few more grains of salt. I asked Prof. Robert Weinberg of MIT, famed for his research on cancer-related genes or "oncogenes," what the public should make of this new antioxidant-cancer link. His emailed reply:
I would say that it is very difficult to extrapolate the results of this study to human beings, even hard to issue a caution about overdosing on antioxidants, since there is so much evidence that usually they do a lot of good. To my mind, this study only becomes meaningful (as well as it was done,) once others have explored the effects of antioxidants in other tumor systems, and that the effects that they observed might be very idiosyncratic for one kind of tumor triggered by one type of oncogene in mice.
Bergö made a similar point himself to reporters.
This new study is just one piece of the puzzle, he said, and one of the next tasks is to "understand the scope of this. We need to understand if this is limited to lung cancer, perform those experiments." Researchers also need to understand, he said, "if antioxidants actually can accelerate the growth of other tumors — like malignant melanoma, leukemia, gastro-intestinal tumors — and we don’t really know anything about that. It's possible it could increase the growth of some cancers but it's possible it will prevent others."
So OK, much remains unknown, but are we at the point — given other recent studies as well — where it no longer makes sense to take Vitamin E supplements? I asked Dr. Mohsen Meydani, an expert on antioxidants — particularly Vitamin E — and director of the Vascular Biology Laboratory at the USDA Human Nutrition Research Center on Aging at Tufts University.
He answered that we can get plenty of Vitamin E from eating a healthy diet. "If we're getting enough fruits and vegetables every day — five servings, for example — we're getting enough of all these antioxidants, all these vitamins, that we need, basically," he said.
Some people may react to the study by saying the implications are that they should stop eating fruits and vegetables, but "that's not the case," he said. The study was well done, but more research is needed both in animals and in humans.
"We have to wait and see," he said.