Oxidative stress and antioxidants
Oxidative Stress (OS) is a general term that describes a steady state level of oxidative damage in cells, tissues, or organs (and so the whole body), caused by the reactive oxygen species (ROS or free radicals) (Genox Corp., 2003).
Cellular oxidative stress results from exogenous sources such as exposure to alcohol, medications, trauma, cold, toxins or radiation, cigarette smoke, environmental pollutants such as emission from automobiles and industries, asbestos, exposure to ionizing radiation and bacterial, fungal or viral infections. Free radicals and peroxides are generated through metabolism of oxygen and exist inherently in all aerobic organisms. These reactive oxygen species are generated by endogenous sources as by-products of normal and essential metabolic processes. Normal energy generation by mitochondria or the detoxification activities of the liver cytochrome P-450 enzyme system produces free radicals. Athletes under heavy training routines or regimes are prone to oxidative stress.
Various stresses deplete specific cellular antioxidants such as glutathione, vitamin C or vitamin E. Oxidative stress plays a role in a wide range of degenerative disorders suh as cancer, diabetes, premature aging, a variety of liver diseases, breast cancer and Alzheimer's disease.
The the body's intra-cellular health is determined by its oxidative stress status and the antioxidant reserve. Serum lipid damaged by oxidants leads to measurable, elevated serum peroxide levels and reflects excessive free radical activity. Free radicals increase with increasing metabolic activity (exercise, fighting off disease etc). Aging and associated degenerative diseases are partly associated with the deleterious side-effects of free radicals on cells. Antioxidants play a very important role in helping to protect cells against free radical oxidative damage.
An organism under increased exposure to reactive oxygen species, that is not countered by antioxidants, experiences free radical-induced alterations of cellular components. Protection against these oxidant species is provided by many different natural antioxidants that may be small molecules, such as tocopherol and ascorbate, and larger enzymes such as superoxide dismutase and glutathione peroxidase. Antioxidants are our body’s first line of defense against free radical damage, and are critical for maintaining optimum health and wellbeing.
Free Radicals, Reactive oxygen species (ROS)
ROS (free radicals) react with cellular membrane lipids, nucleic acids, proteins and enzymes, and other small molecules, resulting in many forms of cellular damage or degeneration. Free radicals are electrically charged molecules. Their unpaired electron, acts like a magnet, causing it to capture electrons from other substances and become neutralized. Although the the free radical is neutralized, another free radical is formed in the chemical process, causing a chain reaction to occur. If subsequent free radicals are not deactivated, thousands of free radical reactions can occur within seconds in a type of cascade reaction. Antioxidants deactivate the free radicals, stopping the cascade reactionin the cells. In this way, antioxidants are absolutely critical for maintaining optimal cellular and systemic health and well-being.
Measuring Oxidative Stress
Oxidative Stress is gauged through measures of blood glutathione, lipid peroxides, Glutathione peroxidase (GSH-Px), Superoxide dismutase (SOD) and two derivatives of salicylate: catechol and 2, 3-dihydroxybenzoate (2,3-DHB). Glutathione is the body’s natural antioxidant (in the form of glutathione peroxidase) and also acts as a detoxifying agent in the liver. Toxins such as nicotine and caffene can therefore deplete natural reserves. The glutathione peroxidase enzyme is found in the cytoplasm (70%) the mitochondria (30%) and requires four selenium atoms per active molecule. Lipids oxidation of mitochondrial and cell membranes would have a deleterious effects on cell function and is prevented by GSH-Px. It also helps in the regeneration of Vitamin C.
The body’s level of oxidative stress is a balance between the rate at which oxidative damage is induced and the rate at which it is efficiently repaired and removed. This repair and removal requires antioxidants, hence the nutritional component to the management of oxidative stress. Contributing factors are an individual's hereditary (genetic) propensity, environment and lifestyle (including diet). Modern life-style habits cause many people to develop abnormally high level of oxidative stress that could lead to an early incidence of age-related diseases. The rate at which damage is removed is dependent on the body’s level of repair enzymes.