What is Oxidative Stress?

Oxidative stress or oxidative cell damage occurs when there is an accumulation of free radicals. These radicals are harmful oxygen-derived chemicals called reactive oxygen species (ROS).

Normally these free radicals are promptly neutralized by efficient antioxidant mechanisms found within the cell. When there is an over-accumulation of free radicals and the antioxidant mechanism is not able to cope it results in oxidative cell damage or injury. Oxidative injury is also referred to as free radical derived cell injury.

Free radicals are highly reactive with other molecules in the body because they have an uneven number of electrons. Some of these reactions can be harmful and cause tissue damage.

Antioxidants are the antidote chemicals as they are capable of giving an electron to the free radical without becoming unstable. Thus, the free radical stabilizes and becomes less reactive.

Research has shown that most of the process of biological aging and degenerative diseases are caused by the deleterious effect of free radical reactions. The common degenerative diseases include atherosclerosis, cancer, asthma, diabetes, senile dementia, inflammatory joint disease and degenerative eye disease. The eye is particularly prone to injury by free radicals.

The most important oxygen-containing free radicals (reactive oxygen species or ROS) implicated in many disease conditions are -

  • Hydroxyl radical
  • Hydrogen peroxide
  • Superoxide anion radical
  • Oxygen singlet
  • Nitric oxide radical
  • Hypochlorite
  • Peroxynitrite radical

Some of the key antioxidants such as glutathione, ubiquinol, and uric acid, are formed during normal metabolic processes in the body. Other antioxidants are obtained from the diet. There are numerous enzyme systems (superoxide dismutase, catalase, glutathione peroxidase) in the body that play a role in the removal of free radicals. However, they need the presence of  vitamin E (á-tocopherol), vitamin C (ascorbic acid) or beta-carotene. The body cannot synthesize these micronutrients, and these have to be supplied in the diet.

Not all free radical reactions are harmful and not all cause disease. Production of free radicals is actually one of the defense mechanisms of the immune system to destroy and eliminate pathogens and microorganisms that attack the body.


  1. Free radicals, antioxidants and functional foods: Impact on human health - (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5922001/)
  2. Laboratory assessment of oxidative stress in semen - (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3249911/)

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