By Adrien Baccichetti (biologist).
Every living being naturally produces, on contact with the oxygen in the air, free radicals (reactive oxygen species) responsible for oxidative stress. These molecules have an unpaired electron that is highly reactive and can attack cell membranes. We possess enzymes (catalase, superoxide dismutase, glutathione peroxidase) or molecules (vitamin C, vitamin A, vitamin E, zinc, silicon) that defend us against this oxidative stress. Exposure to pollutants, drugs, or radiation increases oxidative stress, and the body’s defense system can be overwhelmed. Introducing antioxidants through diet or dietary supplements can help the body defend itself.
Oxidative stress is one of the mechanisms that explains aging. Aging is accompanied by anatomical, physiological, and psychological changes due to biological mechanism alterations. Particularly characteristic signs of aging include:
Brain level: mental disorders, cognitive disorders, memory loss, decreased concentration.
Hormonal level: menopause, andropause.
Skin level: loss of tissue elasticity.
Cardiovascular disorders.
Musculoskeletal disorders, bone and joint problems.
Aging leads to chronic disorders such as joint and inflammatory diseases, cardiovascular problems, cataracts and macular degeneration of the eye, Alzheimer’s and Parkinson’s diseases, and cancers. Oxidative stress is a common factor in these pathologies. Also, the lack of silicon, as after the age of 50, the body’s silicon reserves decrease, and they are essential for tissue support structures, collagen formation, and calcium assimilation by bones. Numerous studies show that intake of antioxidants and silicon can have a protective effect against aging mechanisms.
The body’s defense systems.
The body has various methods to defend against oxidative stress. There are enzymatic defenses, non-enzymatic defenses at the membrane level, and defenses at the cytosol level (inside cells).
1. Enzymatic defenses.
The following diagram illustrates the antioxidant enzymatic defense mechanism. It involves the following enzymes:
Superoxide dismutase (SOD) and catalase (CAT): SOD metabolizes the free radical superoxide O2° into H2O2 (hydrogen peroxide), which is further degraded by catalase (CAT) into H2O and O2. SOD requires copper, zinc, and manganese to function properly, and CAT requires iron, minerals that must be supplied by the diet. Malfunctioning of these enzymes leads to massive oxidative stress, causing numerous cancers, muscle loss with aging, obesity, or cataracts. Improper functioning of SOD is implicated in Charcot’s disease, which leads to motor neuron destruction and eventual death within a few years.
Glutathione peroxidase (GPx): This enzyme, like CAT, metabolizes toxic peroxides into harmless compounds. It needs glutathione as a substrate to function, which is regenerated by glutathione reductase (GR).
2. Non-enzymatic defenses.
These are molecules that trap the singlet electrons of free radicals to inactivate them.
At the membrane level, β-carotenes, vitamin E, and flavonoids play a protective role. They are present in 100 g of nettle at 5 mg, 14.4 mg, and 2 g, respectively.
At the cytosol level, flavonoids and vitamin C (300 mg per 100 g of nettle) perform this role.
3. Conclusions.
Oxidative stress is naturally produced in the body on contact with oxygen and contributes to aging. External factors due to modern lifestyle accentuate this oxidative stress that surpasses the body’s defenses. To defend itself, the body needs minerals (cofactors of detoxification enzymes) such as zinc, manganese, copper, or iron, as well as elements like vitamin C, vitamin E, beta-carotene, and flavonoids. See the nutritive value of nettle.
This may explain the results of the following studies conducted on nettle extracts and oxidative stress. See nettle, silicon, and antioxidant activity.