For more than 40 years, the prevailing explanation of why people get old has been tied to the theory of oxidative stress, or essentially the buildup of harmful molecules. But researchers at McGill University now say this theory may be bunk, after showing that some organisms actually live longer when their ability to clean themselves of this toxic molecule buildup is partially disabled.

 

When molecules like free radicals, oxygen ions, and peroxides build up in cells, they overwhelm the cells’ ability to repair the damage they cause, leading the cells to age, or so the theory went. The belief in the perils of oxidative stress has given rise to an industry of antioxidant therapies. Manufacturers hawk mega-doses of supplements, ranging from vitamin E to C0Q10, as a means to fight the ravages of aging. But clinical trials have not shown that these treatments have statistically significant effects. Writing in a study published in journal PLoS Genetics, the researchers say the reason for the lack of success is that the theory of oxidative stress.

Most of the evidence for the oxidative stress theory is circumstantial, says Siegfried Hekimi of McGill’s Department of Biology, says. He says oxidative stress could just as easily be a result of aging as its cause. “The problem with the theory is that it’s been based purely on correlative data, on the weight of evidence,” says Hekimi. “It is true that the more an organism appears aged, whether in terms of disease, or appearance or anything you care to measure, the more it seems to be suffering from oxidative stress. This has really entrenched the theory because people think correlation is causation.”

 

The researchers studied mutant Caenorhabditis elegans worms. They progressively disabled five genes responsible for producing a group of proteins called superoxide dismutases, which detoxify one of the main reactive oxygen species molecules, which refers to the molecules that build up. Earlier studies seemed to show that decreased production of these detoxifying proteins shortened an organism’s lifespan, but the researchers found the opposite.

 

None of their mutant worms showed decreased lifespan compared to wild-type worms, even though oxidative stress was clearly raised. In fact, one variety actually displayed increased lifespan, the researchers say.

 

The researchers are quick to note that they are not suggesting that oxidative stress is good for you. But they say while it does cause damage to the body, it does not appear to be responsible for aging.