The fashion is to take supplements rich in antioxidants supposed to fight against free radicals and their harmful effects on health. However, the role of oxygen and its derivatives is very complex and ambivalent. Oxygen is essential to life, but its metabolites, free radicals, generate oxidative stress, which has long been suspected of contributing to aging and the development of several diseases including cancer. But these molecules are also absolutely essential for maintaining good health and would contribute to an increase in life expectancy.
The bad reputation of free radicals
Over the years, most of the phenomena associated with aging have been attributed to the presence of free radicals formed during metabolism. These very unstable molecules can indeed “attack” all the elements that are within their reach and cause significant damage to DNA, proteins and membranes.
According to the free radical theory, the accumulation of this damage over time exceeds the natural antioxidant capacities of our cells, which would explain the gradual deterioration in the functioning of the body that occurs with aging and the outbreak of diseases such as cancer, heart disease or neurodegeneration.
A certain protective effect against free radicals
However, free radicals do not only have harmful effects on the organism: regular physical exercise, for example, generates large quantities of free radicals, but nevertheless represents one of the main lifestyle factors which make it possible to prevent development and recurrence of several cancers. Free radicals also participate in the attack of immune cells against pathogens, as well as in the elimination of abnormal precancerous cells by the process of apoptosis.
In clinical practice, it is also thanks to the free radicals generated by chemotherapy or radiotherapy that many tumors can be eradicated, the oxidative stress generated by these treatments being absolutely essential for the elimination of cancerous cells.
It is also strongly advised against taking antioxidant supplements during and after radiotherapy treatment, as studies indicate a reduction in the effectiveness of radiation and a significant increase in the risk of recurrence.
These observations therefore indicate that the impact of free radicals is much more nuanced than what is conveyed by the supplement industry and that these molecules could play complex roles in the balance of the organism.
Free radicals help cells protect themselves and increase life expectancy
One of the most intriguing aspects of free radicals is their positive impact on the longevity of simple organisms like the worm Caenorhabditis elegans. For example, several studies have shown that the generation of free radicals is associated with a marked increase in the lifespan of this organism, a positive impact that is reversed by antioxidant supplements.
A research team has shown that this increase in longevity is caused by an activation of the pathways involved in the elimination of cells (apoptosis). Instead of leading to cell death, free radicals cause several changes in the expression of genes that make the cell more resistant to stress and will, on the contrary, increase its lifespan.
In other words, free radicals would not be a cause of aging, but could on the contrary help cells to fight the deterioration of their functions that occurs over time.
Too many antioxidants are harmful to health
These observations are very interesting. In recent years, a very large number of studies have clearly demonstrated that high doses of antioxidants do not reduce the risk of disease in any way and could even, in certain cases (vitamin E, in particular), reduce life expectancy. of life. It is likely that abnormally high concentrations of antioxidants taken in the form of supplements interfere with certain important functions performed by free radicals and thereby disrupt the normal functioning of the body.
Take care of your diet and your lifestyle: that should be enough
As always, the right attitude is one of finding a balance. No need to hunt free radicals at all costs with antioxidant tablets, but on the other hand, our overexposure to pollution, the consumption of junk food and various other negative factors cause the number and activity of radicals to explode. free. Therefore, before using commercial antioxidants, make sure that your diet (Mediterranean type or at least rich in fruits and vegetables with 5 to 10 portions / day) and that your lifestyle provide you with everything your body needs. needs for its antioxidant balance.
Ristow M and Schmeisser S. Extending life span by increasing oxidative stress. Free Radic Biol Med; 51: 327-36.
Yee C et al. The intrinsic apoptosis pathway mediates the pro-lonevity response to mitochondrial ROS in C.elegans. Cell, 157: 897–909.