Forget the antioxidants? Researchers cast doubt on role of free radicals in aging

February 17, 2009

For more than 40 years, the prevailing explanation of why we get old has been tied to what is called oxidative stress. This theory postulates that when molecules like free radicals, oxygen ions and peroxides build up in cells, they overwhelm the cells’ ability to repair the damage they cause, and the cells age.

An industry of “alternative” antioxidant therapies -- such as Vitamin E or CoQ10 supplements in megadose format --has sprung up as the result of this theory. However, clinical trials have not shown that these treatments have statistically significant effects.

And now researchers at McGill University , in a study published in the February issue of the journal PLoS Genetics, are calling the entire oxidative stress theory into question. Their results show that some organisms actually live longer when their ability to clean themselves of this toxic molecule buildup is partially disabled. Collectively, these molecules are known as reactive oxygen species, or ROS for short.

Dr. Siegfried Hekimi of McGill's Department of Biology, said most of the evidence for the oxidative stress theory is circumstantial, meaning 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,” explained Hekimi, McGill’s Strathcona Chair of Zoology and Robert Archibald & Catherine Louise Campbell Chair in Developmental Biology. “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,” he continued, “because people think correlation is causation. But now this theory really is in the way of progress.”

Hekimi and postdoctoral fellow Jeremy Van Raamsdonk studied mutant Caenorhabditis elegans worms. They progressively disabled five genes responsible for producing a group of proteins called superoxide dismutases (SODs), which detoxify one of the main ROS. Earlier studies seemed to show that decreased SOD production shortened an organism’s lifespan, but Hekimi and Van Raamsdonk did not observe this. In fact, they found quite 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 said.

“The mutation that increases longevity affects the main SOD found in mitochondria inside the animals’ cells,” said Hekimi. “This is consistent with earlier findings that mitochondria are crucial to the aging process. It seems that reducing mitochondrial activity by damaging it with ROS will actually make worms live longer.”

The researchers hasten to point out that they are not suggesting that oxidative stress is good for you.

“ROS undoubtedly cause damage to the body,” Hekimi said. “However, they do not appear to be responsible for aging.”

More information: dx.plos.org/10.1371/journal.pgen.1000361

Provided by McGill University

Explore further: Something in the water—life after mercury poisoning

Related Stories

Something in the water—life after mercury poisoning

September 26, 2017

From 1932 to 1968, hundreds of tonnes of mercury seeped into the clear waters of Minamata Bay, Japan, causing health and environmental problems still felt today. As the first global treaty on mercury finally comes into force, ...

Prevailing theory of aging challenged in Stanford worm study

July 24, 2008

Age may not be rust after all. Specific genetic instructions drive aging in worms, report researchers at the Stanford University School of Medicine. Their discovery contradicts the prevailing theory that aging is a buildup ...

Researchers use banned herbicide to prolong worms' life

December 8, 2010

It sounds like science fiction – Dr. Siegfried Hekimi and his student Dr. Wen Yang, researchers at McGill's Department of Biology, tested the current "free radical theory of aging" by creating mutant worms that had increased ...

Worms control lifespan at high temperatures

April 16, 2009

The common research worm, C. elegans, is able to use heat-sensing nerve cells to not only regulate its response to hotter environments, but also to control the pace of its aging as a result of that heat, according to new ...

Mitochondrial process may predict lifespan of organisms

February 24, 2014

The complexity in biology is astounding. That is why biologists are thankful that model organisms, like the roundworm Caenorhabditis elegans, can be used to breakdown biological processes into simpler units.

Recommended for you

Energy-saving LEDs boost light pollution worldwide

November 22, 2017

They were supposed to bring about an energy revolution—but the popularity of LED lights is driving an increase in light pollution worldwide, with dire consequences for human and animal health, researchers said Wednesday.

Re-cloning of first cloned dog deemed successful thus far

November 22, 2017

(Phys.org)—A team of researchers with Seoul National University, Michigan State University and the University of Illinois at Urbana-Champaign has re-cloned the first dog to be cloned. In their paper published in the journal ...

Testing the advantage of being left-handed in sports

November 22, 2017

(Phys.org)—Sports scientist Florian Loffing with the Institute of Sport Science, University of Oldenburg in Germany has conducted a study regarding the possibility of left-handed athletes having an advantage over their ...

5 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

deatopmg
not rated yet Feb 17, 2009
BFD - this is for a nematode worm. higher forms of life show the opposite effect.
taisha99
not rated yet Feb 18, 2009
Its a WORM ! and a simple one at that
ZeroDelta
not rated yet Feb 18, 2009
I am less concerned with anitoxidants and aging as opposed to dmamage to DNA, RNA and cell funtion, as stated in the article.
Keter
not rated yet Feb 18, 2009
I'm not giving up my antioxidant routine (which works) based on this: there are worms that thrive in the toxic environments around volcanic fumaroles, too - does that mean I should live downwind of a toxic smokestack? (insert gutteral sound of disgust here)
holmstar
not rated yet Feb 18, 2009
animals also tend to live longer when their metabolism is reduced. Seems pretty likely that damaging the mitochondria would have a negative effect on metabolism, thus we get the same result of lower metabolism = longer life.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.