Free radicals are actually atoms or groups of atoms having an odd (or unpaired) number of electrons and are formed on the interaction of oxygen with certain molecules. Once formed, they begin a chain reaction and being highly reactive, react with important cellular components such as the cell membrane or DNA and can cause immense damage. This may cause the cells to function poorly or die. To prevent the damage caused by free radicals there is a defence system of antioxidants in the body.

Antioxidants are also molecules that safely react with free radicals and terminate the chain reaction before vital cellular components are damaged. Vitamin E, vitamin C and beta-carotene are the principle micronutrients that restrict the free radicals from reacting and causing damage.

Selenium, a trace metal required for the functioning of one the antioxidant enzyme systems body is sometimes also included in this category. These micronutrients have to be supplied to the body through the diet as it is not manufactured by the body.

Vitamin E: This is a fat soluble vitamin and is present in seeds, nuts, fish oils, vegetables, whole grains (especially wheat), apricots and fortified cereals. The current recommended daily allowance or RDA is 12 IU per day for women and 15 IU per day for men.

Vitamin C: Vitamin C or Ascorbic acid is a vitamin that is water soluble and is present in juices and citrus fruits, cabbage, spinach, green peppers, broccoli, cantaloupe, kale, kiwi and strawberries. 60 mg is the RDA per day. Intake of more than 2000 mg of this vitamin may have adverse side effects.

Beta-carotene is vitamin A's precursor (retinol) and is present in egg yolk, liver, butter, milk, carrots, spinach, broccoli, squash, yams, peaches, tomato, cantaloupe, and grains. On account of it being converted to vitamin A there is no specific requirement in the body. The RDA is expressed as retinol equivalents (RE). Vitamin A does not have any antioxidant properties and can be toxic if taken in excess.

Preventing heart disease and cancer - how do antioxidants help?

Epidemiologic observations demonstrate lower rates of cancer in people having diets that are rich in vegetables and fruits. Because of this fact, a theory developed stating that these foods contained certain substances that acted against the development of cancer, but there is no scientific evidence to prove this fact.

Thus some studies and research reveal that dietary supplements along with increased level of antioxidants reduce the risk of developing cancer. Antioxidants may have a role top plat in slowing process of aging and preventing strokes, and heart disease but this is still not conclusive.

Exercise and oxidative damage

Exercise increases oxygen utilization 10 to 20 times more than in the resting state. This increases the generation of free radicals greatly which then prompts concerns about damage to tissues and muscles. The question that now arises is that how effectively can athletes defend their bodies against the increased free radicals that result from exercise? Do they require taking extra antioxidants?

Since it is not possible to measure the amount of free radicals in the body physically; this can be done by measuring the by-products resulting from free radical reactions. If the free radicals exceed the antioxidant defense mechanisms of the body then there would be more by-products. Athletes are seen to perform these measurements to enable derive at the free radical amount.

These experimental studies have revealed certain facts that regular physical exercise enhances the antioxidant defense system of the body and protects it against intense exercise induced free radical damage. This is a vital finding because it illustrates the smartness of the body in adapting to the exercise demands.

On the contrary, intense exercise patterns among untrained individuals induce damage to antioxidant defenses resulting in enhanced free radical damage.