How does reactive oxygen species harm our body?

Mitochondria are also known as the cell’s power house within aerobic organisms and they supply energy to the cell. During this process of energy production via respiratory chain, oxygen gets converted to water. This reduction of oxygen leads to the production of chemically reactive molecules like •O₂^- (Superoxide anion), •OH (hydroxyl ion) and H₂O₂ (hydrogen peroxide), OCl^- (hypochlorite ion) etc. These molecules are also known as free radicals or reactive oxygen species (ROS). They are highly reactive as they contain unpaired elector which waits to get paired and attain stability.

There are several mechanisms involved in their production. These free radicals are continuously generated during the process of cellular respiration. At least 1-2% of oxygen utilized by the cell fails to form water rather gets converted into free radical, •O₂^-(Superoxide anion). During the battle between the WBCs and pathogens, free radicals are generated. Some external sources which aggravate the formation of free radicals are exposure to ultraviolet radiations, drugs and pollutants like cigarette smoke and toxic chemicals.

Free radicals have been detected to cause damage to a variety of biomolecules. It damages the basic genetic material of the cell that is DNA and RNA. They act as mutagens ultimately leading to cancer. These mutations tend to get accumulated with increasing age. It affects the proteins stimulating structural changes as a result of which the enzymes or hormones loose their functions. One of the most damaging effects of ROS is lipid peroxidation of polyunsaturated fats. As a result the cell membranes and the lipoproteins which help in the transportation of lipids are hampered. Lipid peroxidation has a prominent role in increasing the intensity of cardiovascular problems and diabetes.

Our body has a defense mechanism which neutralizes the free radicals so formed. Enzymes like superoxide dismutase and catalase help in detoxifying free radicals. Now- a-days the concentration of free radicals within human cells has been found to be very high. This higher concentration is due to the drastic changes in the life style habits of the modern man and increasing pollution. The levels of these reactive species have been found to be so high that body’s self defense mechanism fails to fight against them. In such conditions it is very essential that man consumes a lot of antioxidants which can fight against these free radicals. The defensive system organized by the antioxidants protects the human body at multiple levels. They act as scavengers and remove the excess of ROS generated within our body. Antioxidant enzymes like catalase and superoxide dismutase perform their function within the cell where as the small molecule antioxidants scavenge the ROS present within the extracellular space and blood. Vitamins obtained from fruits and vegetables act as small molecule antioxidants. Alpha-tocopherol obtained from vitamin E prevents lipid peroxidation and acts as a strong antioxidant. Carotenoids like beta-carotene (rich in Vitamin A sources of food), alpha-carotene, lutein and lycopene (found in tomatoes) are considered to be good antioxidants. Water soluble vitamin likes vitamin C, scavenges a large variety of free radicals. Some flavonoids obtained from plants also show antioxidant properties.

In a nut shell a conscious effort to modulate out diet can bring great positive results. Consumption of whole grains, fruits and vegetables can relieve us of free radicals. This will protect us not only from deadly diseases like cancer but also act as anti-ageing substances.