We here at the American Council on Science and Health are basically dubious to the max on the relevance of animal studies (especially rodent tests) to human health and physiology, as you may know. So we take this mouse experiment with a grain (or a pound) of salt. But when an animal study comports with other studies, including human ones, we are allowed to take note of it at least.
A group of researchers from the University of Gothenburg in Sweden studied the effects of two antioxidant substances, vitamin E and n-acetylcysteine (NAS), on tumor cells in mice bred to be cancer-prone. They also planned to investigate the mechanisms involved in causing the effect on tumor cells, whether promotion or suppression of growth. The study was published in this week s Science Translational Medicine.
The results were not good, for the mice anyway: the antioxidant-fed mice had a 2.8-fold increase in lung tumors; further, the tumors behaved in a more invasive and aggressive pattern, and the mice died twice as quickly, as compared to mice not given antioxidants. When the antioxidants were added to human lung tumor cells in lab dishes, they also accelerated those cells growth.
One important advance in the study was determining how the accelerated tumor cell growth was provoked. They found that the antioxidants did in fact decrease DNA damage, but that the damage was rendered insufficiently severe, and so became undetectable by the cell. The cell therefore did not deploy its cancer-defense system, which is based on a protein called p53. By allowing cancer cells to stay below the radar of p53, antioxidants allow tumors to thrive, the study found.
The new antioxidant study seems quite sound," Eliseo Guallar, professor of epidemiology at Johns Hopkins School of Public Health, told Reuters reporter Sharon Begley. "It's unfortunate that the public has the idea that vitamin supplements are good and antioxidants are better."
However, most cancer specialists would likely caution against basing public health advice on a mouse study. You can t extrapolate from this study to make a recommendation to people, Barry Kramer, director of the Division of Cancer Prevention at the National Cancer Institute in Bethesda, Maryland, told Science magazine. He notes that the science of antioxidants is complicated and that the results of mice studies often don t apply to humans. Still, Kramer and others say the new findings demand further exploration.
Here is what the National Cancer Institute fact sheet says on this topic:
Research in humans has not demonstrated convincingly that taking antioxidant supplements can help reduce the risk of developing or dying from cancer, and some studies have even shown an increased risk of some cancers.
And here is a huge JAMA study showing this:
Antioxidant supplements are not associated with lower all-cause mortality. Beta carotene, vitamin E, and higher doses of vitamin A may be associated with higher all-cause mortality.
ACSH s Dr. Gilbert Ross had this perspective: Obviously, for the umpteenth time, Mice are NOT little people. OK, but when numerous previous studies have either failed to show any benefit for the group of substances called antioxidants, or actually shown harm associated with their use as supplements, we here at ACSH ask: Why take the risk of trying to enhance your health when anyone eating a balanced diet will consume these same chemicals in appropriate doses? It seems that taking higher-dose forms in a supplement leads to either no change or worse health, so don t do it.
ACSH s Dr. Josh Bloom adds, Free radicals the target of antioxidants exist because they serve a purpose. We need them. (For more information, see an NIH article on this topic). So, once again we are guinea pigs for unapproved drugs, which are marketed shamelessly by the supplement industry. And guess what? The usual story: unknown risk, unknown benefit. I think I ll pass.