By: Dr. Abhishek Pandey, Asstt. Editor-ICN
LUCKNOW: An antioxidant can be defined as: “any substance that when present in low concentrations compared to that of an oxidisable substrate significantly delays or inhibits the oxidation of that substrate”. The physiological role of antioxidants, as this definition suggests, is to prevent damage to cellular components arising as a consequence of chemical reactions involving free radicals.
Examples of antioxidants include-
- Vitamin A
- Vitamin C
- Vitamin E
Vegetables and fruits are rich sources of antioxidants. There is good evidence that eating a diet with lots of vegetables and fruits is healthy and lowers risks of certain diseases. But it isn’t clear whether this is because of the antioxidants, something else in the foods, or other factors.
FUNCTIONS OF ANTIOXIDANTS
- It reduces the free radicals.
- It stimulates the growth of normal cells.
- Protects cells against premature and abnormal ageing.
- Helps fight age related molecular degeneration.
- It supports the body immune system
Antioxidants are the components produced by the body to neutralize the effect of free radicals, but the effect will be limited to specific antioxidants. In human body oxidants and anti oxidate ratio will be maintained, any alteration in these oxidants and antioxidate will causes accumulation of ROS within the body, this process is called as oxidative stress. Oxidative stress has an important role in tissue damage and leads to pathological conditions such as cancer.
Oxidants and antioxidants may play a role in the last stages of cancer development. At this stage the levels of antioxidants play a very crucial role in prevention and progression of carcinogenesis. The human body has an inherent mechanism for protection against free radicals and other ROS called as antioxidant stress, it is defined as a “persistent imbalance between antioxidants and pro-oxidants in favor of the latter, resulting in irreversible cellular damage.” They act by scavenging them, suppressing their formation or opposing their action.
Are antioxidant supplements necessary for individuals who exercise regularly? Should antioxidant supplements be part of the “nutritional game plan” of athletes?
These are common questions directed to fitness leaders, athletic trainers, and other health professionals who are consulted about the role of antioxidants in a healthy, active lifestyle. The reason for this interest in antioxidants is the finding that highly reactive chemical species, called free radicals, may increase during exercise. A free radical is broadly defined as a molecule containing ≥1 unpaired electrons in its outer orbit. During oxidative metabolism, much of the oxygen consumed is bound to hydrogen during oxidative phosphorylation, thus forming water. However, it has been estimated that 4–5% of the oxygen consumed during respiration is not completely reduced to water, instead forming free radicals. Thus, as oxygen consumption increases during exercise, a concomitant increase occurs in free radical production and lipid per oxidation. The body contains an elaborate antioxidant defense system that depends on dietary intake of antioxidant vitamins and minerals and the endogenous production of antioxidant compounds such as glutathione. Vitamins C and E and beta-carotene are the primary vitamin antioxidants. In addition to glutathione, there are numerous enzymes involved in the quenching or removal of free radicals.
Free radicals are highly unstable molecules that are naturally formed when you exercise and when your body converts food into energy. Your body can also be exposed to free radicals from a variety of environmental sources, such as cigarette smoke, air pollution, and sunlight. Free radicals can cause “oxidative stress,” a process that can trigger cell damage. Oxidative stress is thought to play a role in a variety of diseases including cancer, cardiovascular diseases, diabetes, Alzheimer’s disease, Parkinson’s disease, and eye diseases such as cataracts and age-related macular degeneration.
Vitamin E is the major lipid-soluble antioxidant in cell membranes. It protects against lipid per oxidation by acting directly with a variety of oxygen radicals, including singlet oxygen, lipid peroxide products, and the superoxide radical, to form a relatively innocuous tocopherol radical. Vitamin C can interact with the tocopherol radical to regenerate reduced tocopherol. Vitamin C is water soluble and can directly react with superoxide, hydroxyl radicals, and singlet oxygen. Beta-carotene, the major carotenoid precursor of vitamin A, is the most efficient “quencher” of singlet oxygen.
- High-dose antioxidant supplements may be harmful in some cases. For example, the results of some studies have linked the use of high-dose beta-carotene supplements to an increased risk of lung cancer in smokers and use of high-dose vitamin E supplements to increased risks of hemorrhagic stroke (a type of stroke caused by bleeding in the brain) and prostate cancer.
- Like some other dietary supplements, antioxidant supplements may interact with certain medications. For example, vitamin E supplements may increase the risk of bleeding in people who are taking anticoagulant drugs (“blood thinners”).
There is conflicting evidence on the effects of taking antioxidant supplements during cancer treatment; some studies suggest that this may be beneficial, but others suggest that it may be harmful. The National Cancer Institute recommends that people who are being treated for cancer talk with their health care provider before taking supplements.
Excessive free radicals contribute to chronic diseases including cancer, heart disease, cognitive decline, and vision loss. This doesn’t automatically mean that substances with antioxidant properties will fix the problem, especially if they are taken out of their natural context. The studies so far are inconclusive but generally don’t provide strong evidence that antioxidant supplements have a substantial impact on disease.
Keep in mind that most of the trials conducted have had fundamental limitations due to their relatively short duration and inclusion of people with existing disease. At the same time, abundant evidence suggests that eating whole in fruits, vegetables, and whole grains—all rich in networks of naturally occurring antioxidants and their helper molecules—provides protection against many scourges of aging.
Free radical can damage the cell, it can be reversible or irreversible this will be depending up on external factors such as environmental or biochemical agents. The damage to the cell is reversible depending up on the levels of antioxidant stress. Antioxidants acts like first line of defense for protection of cells. Increased intake of antioxidants in the diet will help maintain cell integrity and also the normal physiological and biochemical functions of living system. The antioxidants help in neutralizing the free radicals and thus protect the cells.