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

Feb 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: Stanford researchers rethink 'natural' habitat for wildlife

add to favorites email to friend print save as pdf

Related Stories

Researchers use banned herbicide to prolong worms' life

Dec 08, 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 ...

Biologists identify a new clue into cellular aging

Jul 07, 2010

The ability to combat some age-related diseases, such as cancer and diabetes, may rest with scientists unlocking clues about the molecular and cellular processes governing aging. The underlying theory is that if the healthy ...

Recommended for you

Plants with dormant seeds give rise to more species

21 hours ago

Seeds that sprout as soon as they're planted may be good news for a garden. But wild plants need to be more careful. In the wild, a plant whose seeds sprouted at the first warm spell or rainy day would risk disaster. More ...

Researchers successfully clone adult human stem cells

Apr 18, 2014

(Phys.org) —An international team of researchers, led by Robert Lanza, of Advanced Cell Technology, has announced that they have performed the first successful cloning of adult human skin cells into stem ...

User comments : 5

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.

More news stories

Plants with dormant seeds give rise to more species

Seeds that sprout as soon as they're planted may be good news for a garden. But wild plants need to be more careful. In the wild, a plant whose seeds sprouted at the first warm spell or rainy day would risk disaster. More ...

Researchers successfully clone adult human stem cells

(Phys.org) —An international team of researchers, led by Robert Lanza, of Advanced Cell Technology, has announced that they have performed the first successful cloning of adult human skin cells into stem ...

Airbnb rental site raises $450 mn

Online lodging listings website Airbnb inked a $450 million funding deal with investors led by TPG, a source close to the matter said Friday.

Health care site flagged in Heartbleed review

People with accounts on the enrollment website for President Barack Obama's signature health care law are being told to change their passwords following an administration-wide review of the government's vulnerability to the ...

Impact glass stores biodata for millions of years

(Phys.org) —Bits of plant life encapsulated in molten glass by asteroid and comet impacts millions of years ago give geologists information about climate and life forms on the ancient Earth. Scientists ...