Free Radicals and Oxidative Stress
Free radicals are associated with human diseases, including cancer, atherosclerosis, Alzheimer's disease, Parkinson's disease, and many others.
What Are Free Radicals?
In chemistry, a radical is an atom, molecule, or ion that has an unpaired valence electron. Free radicals are unstable atoms that can damage cells, causing illness and aging.
The danger of free radicals
Free radicals are unstable atoms. To become more stable, they take electrons from other atoms. This may cause diseases or signs of aging.
This causes damage to cells, proteins, and DNA.
Antioxidants and free radicals
Antioxidants keep free radicals in check. Antioxidants are molecules in cells that prevent free radicals from taking electrons and causing damage.
Antioxidants are able to give an electron to a free radical without becoming destabilized themselves, thus stopping the free radical chain reaction. "Antioxidants are natural substances whose job is to clean up free radicals.
Just like fiber cleans up waste products in the intestines, antioxidants clean up the free radical waste in the cells," said Wright. Well-known antioxidants include beta-carotene and other carotenoids, lutein, resveratrol, vitamin C, vitamin E, lycopene, and other phytonutrients.
What is Oxidative stress?
Oxidative stress occurs when there are too many free radicals and too much cellular damage.
Oxidative stress is initiated by reactive oxygen species (ROS) that are stabilized through electron pairing with biological macromolecules such as proteins, lipids, and DNA in healthy human cells and, thereby, cause protein and DNA damage and lipid peroxidation (Ames et al., 1993).
Oxidative reactions can produce free radicals, including hydroxyl, peroxyl, and superoxide radicals, which can initiate chain reactions that damage cells (Oyinloye et al., 2015).
These free radicals have been implicated as potential contributors to the pathogenesis of cancer, diabetes, atherosclerosis, cardiovascular diseases, aging, and inflammatory diseases (Braca et al., 2002; Maxwell, 1995).
Consumption of diets that contain foods rich in antioxidants, such as fruits and vegetables, can significantly reduce the risk of many cancers, indicating that such antioxidants could be effective agents for the suppression of carcinogenesis.
What causes oxidative stress?
The generation of reactive oxygen species (ROS) is inevitable for aerobic organisms and, in healthy cells, occurs at a controlled rate.
Oxidative Stress and Diseases
Oxidative stress is now thought to make a significant contribution to all inflammatory diseases (arthritis, vasculitis, glomerulonephritis, lupus erythematous, adult respiratory diseases syndrome), ischemic diseases (heart diseases, stroke, intestinal ischemia), hemochromatosis, acquired immunodeficiency syndrome, emphysema, organ transplantation, gastric ulcers, hypertension and preeclampsia, a neurological disorder (Alzheimer's disease, Parkinson's disease, muscular dystrophy), alcoholism, smoking-related diseases, and many others.
People interested in fighting free radical-related aging should avoid common sources of free radicals, such as pollution and fried food. They should also eat a healthful, balanced diet without worrying about supplementing with antioxidants.
Antioxidant Foods and Supplements
Thousands of chemicals can act as antioxidants. Vitamins C, and E, glutathione, beta-carotene, and plant estrogens called phytoestrogens are among the many antioxidants that may cancel out the effects of free radicals.
Many foods are rich in antioxidants. Berries, citrus fruits, and many other fruits are rich in vitamin C, while carrots are known for their high beta-carotene content. The soy found in soybeans and some meat substitutes are high in phytoestrogens.
The ready availability of antioxidants in food has inspired some health experts to advise antioxidant-rich diets. The antioxidant theory of aging also led many companies to push sales of antioxidant supplements.
Research on antioxidants is mixed. Most research shows few or no benefits. A 2010 study that looked at antioxidant supplementation for the prevention of prostate cancer found no benefits. A 2012 study found that antioxidants did not lower the risk of lung cancer. In fact, for people already at a heightened risk of cancer, such as smokers, antioxidants slightly elevated the risk of cancer.
Some research has even found that supplementation with antioxidants is harmful, particularly if people take more than the recommended daily allowance (RDA). A 2013 analysis [Trusted Source] found that high doses of beta-carotene or vitamin E significantly increased the risk of dying.
A few studies have found benefits associated with antioxidant use, but the results have been modest. A 2007 study, for instance, found that long-term use of beta-carotene could modestly reduce the risk of age-related problems with thinking.