![The role of antioxidants questioned?](https://img.passeportsante.net/1000x526/2014-03-24/i75552-le-role-des-antioxydants-remis-en-question.jpg)
December 21, 2010 – A study on worms1.2, carried out by researchers at McGill University, calls into question the hypothesis3 wanting free radicals to accelerate aging and the onset of disease. For more than 50 years, the free radicals produced by our body have been considered enemies that must be fought when they are in excess. On the other hand, antioxidants, because they can neutralize these molecules, are perceived as good for health.
The study in question
Both authors of the essay scrutinized the longevity of tiny worms (Caenorhabditis elegans) commonly used in laboratory testing. They subjected them to two types of intervention to increase their production of free radicals. One group has been genetically modified so that its defense system preventing the production of these molecules is neutralized; the other group was exposed to a toxic herbicide (paraquat).
Surprise: these two interventions, which a priori were to cause problems, instead increased the lifespan of the worms. In addition, the mutant worms which were subsequently exposed to antioxidants (vitamin C and N-acetylcysteine) lived less. Principal investigator Siegfried Hekimi, professor in the Department of Biology at McGill University, therefore concluded that the hypothesis that links free radicals with aging needs to be reviewed: they are not the cause of aging, but rather contribute to it. combat.
Can we extrapolate to humans?
“Not really,” replies Charles Couillard, professor at the Institute of Nutraceuticals and Functional Foods and at the Department of Food Sciences and Nutrition at Laval University. The trial is scientifically well conducted, but its conclusions should be viewed with caution. Not on their accuracy, but rather on their applicability to humans, he continues. Humans remain a more complex organism than most cell and animal models used in research. The ultimate test will always remain the clinical study in humans to confirm everything. Impossible to escape from it, ”he emphasizes.
An opinion shared by pharmacist Jean-Yves Dionne and nutritionist Hélène Baribeau. “This essay is interesting because it challenges the dogma of free radicals and aging, but how far? It’s not clear. These worms have no organs or a nervous system, ”says Jean-Yves Dionne.
According to him, if a person were deprived of their ability to fight free radicals, as was done with these worms, a series of harmful effects would occur. He adds that free radicals are also allies in certain situations: “We know, for example, that white blood cells, to be more efficient, bombard enemies with free radicals. “We have known for a long time that free radicals play a beneficial role in certain physiological processes,” adds Hélène Baribeau.
Oxidative stress: the cause or the consequence?
Is oxidative stress the cause or consequence of different diseases, such as cancer, diabetes and cardiovascular disease? Or a protection system?
According to Professor Couillard, we must instead ask the following question: “Should we eliminate oxidative stress?” “” Yes and no, he replies. Everyone agrees that transient oxidative stress is necessary for the proper functioning of the human body (inflammation, tissue repair, protection against infections, etc.). On the other hand, it is chronic oxidative stress that must be eliminated, because it is associated with many complications related to chronic diseases. These complications themselves contribute to the development of chronic diseases, he explains. So an excess of free radicals would be both the cause and the consequence of many chronic disorders ”.
What is oxidative stress? Oxidative stress appears when the defense system available to our cells weakens or is overwhelmed by excessive production of free radicals. These are atoms or fragments of molecules that include unpaired (single) electrons. As they are particularly unstable, these electrons seek to stabilize themselves by binding to an electron belonging to another molecule. Result: they destabilize neighboring molecules, causing a chain reaction that causes damage to cells. For example, oxidation of lens proteins can lead to cataracts. Oxidative stress can even disrupt the cell’s program. If the genes responsible for cell division are affected, cancer can be initiated. Oxidative stress would also be a factor contributing to cardiovascular and neurodegenerative diseases (Parkinson’s disease, Alzheimer’s disease). |
Are the antioxidants outdated?
“Antioxidants are not a panacea. Healthy lifestyle habits (nutrition and exercise) generally provide the body with everything it needs from an antioxidant standpoint, ”says Professor Couillard.
“It is true that the preventive effect of antioxidants on chronic diseases is not proven, but it is a logical assumption and it is not dangerous for our health, advances Jean-Yves Dionne. Turmeric supplements, for example, are often the only way to get an effective dose without having to eat Indian food 3 times a day ”.
“Supplements provide isolated and concentrated compounds, but I’m not sure that’s a good point,” says Hélène Baribeau. The advantage of foods, as the work of Richard Béliveau shows, is that they provide both small doses and a wide variety of antioxidants. They thus probably help to maintain a balanced antioxidant-free radical ratio. “
To be continued
Hélène Baribeau believes that, even if this test shakes up certain certainties, it is far too preliminary to change the nutritional recommendations. “The media coverage of this trial may contribute to public confusion about the importance of eating fruits and vegetables,” she worries.
Jean-Yves Dionne believes that it is necessary to develop a clearer discourse and to specify the specificities of the most active antioxidants, the most interesting, otherwise “we will continue to get lost in the fog”. According to Charles Couillard, other studies, on models more evolved than worms, must be carried out to better understand oxidative stress. “In the meantime, we consume fruits and vegetables because they are good, and we will understand later, we hope – and we are working on it – how these benefits are produced, he concludes.
Antioxidants: too general a word The term “antioxidants” includes hundreds of different substances that have different effects and different sites of action. “It’s like the term” drug “, which brings together extremely diverse molecules, explains Jean-Yves Dionne. For example, it is true that coffee contains as many antioxidants as tea, but they are not the same and those in tea are much more interesting! He argues. Charles Couillard sheds additional light: “For fruits and vegetables, scientists are quietly abandoning the name antioxidant. They prefer the words polyphenols or flavonoids. Why? Because we are beginning to observe that the main activity of these compounds is not an antioxidant effect in the blood: they are very little absorbed in the intestine and only stay in the blood for 4 hours or less. It is more and more the activity of polyphenols at the cellular level that we are trying to understand, that is to say their effect on vascular, adipose, muscular, cerebral tissues, etc. Researchers are also looking at the effects of substances produced as a result of the passage of polyphenols through the intestine. “ Molecules that have antioxidant effects have other equally interesting properties, if not even more, confirms Jean-Yves Dionne. This is the case, for example, with curcuminoids, present in turmeric. “Curcuminoids are antioxidants 50 to 100 times more powerful than vitamin E, but it is especially their anti-inflammatory effect and their anticancer effect that interest people. “ The antioxidant basket therefore overflows because of generalization. “When we generalize a lot, we risk making a lot of mistakes,” says Hélène Baribeau. Preliminary trials indicate, for example, that some people are sensitive to the cancer molecule in broccoli and others are not. Our genes would therefore play an important role in this chapter. Nutrigenomics may give us clearer answers in … twenty years! “ |
Françoise Ruby – PasseportSanté.net
1. Denham Harman is a chemist, biologist and medical gerontologist, professor emeritus at the University of Nebraska.
2. Yang W, Hekimi S (2010) A Mitochondrial Superoxide Signal Triggers Increased Longevity in Caenorhabditis elegans. PLoS Biol. 2010 Dec 7; 8 (12): e1000556. Full text: www.plosbiology.org
Note. This team of researchers had published in 2009, a similar study, which had been the subject of a news in our site: Aging: useless, the antioxidants?
3. This hypothesis was formulated in 1957 by Denham Harman, an American specialist in aging.