What is a free radical?
Atoms and molecules are most stable when their electrons are paired. A free radical is an atom or molecule that has an unpaired electron. This makes it very unstable and highly reactive: it tries to grab an electron from a nearby molecule to become stable again. In doing so it damages that molecule and often turns it into a new radical, starting a chain reaction inside the body.
Where do free radicals come from?
The body makes some free radicals naturally during normal metabolism, when cells use oxygen to release energy from food. Their numbers rise sharply because of factors from outside the body:
- Cigarette smoke and vehicle exhaust
- Ultraviolet (UV) rays from strong sunlight
- Air pollution and industrial fumes
- Radiation and some processed or fried foods
Example
When cooking oil is heated again and again at a hawker stall, more free radicals form in the oil. Eating a lot of such repeatedly-fried food adds free radicals to the body.
Why are they harmful?
When free radicals outnumber the body's defences, the result is oxidative stress. The radicals damage cell membranes, proteins and even DNA. Over time this is linked to faster ageing, heart disease and some cancers. A small number of radicals is normal and even useful for fighting germs, but too many cause harm.
The body has its own defences and repair systems, and it also uses antioxidants from the food we eat to mop up extra radicals. Trouble begins only when the number of free radicals produced becomes greater than the body can safely handle, so a healthy lifestyle and a diet rich in fruits and vegetables help keep the balance.
Key idea
A free radical = an atom or molecule with an unpaired electron. It is unstable and reactive, and steals electrons from healthy molecules, damaging cells.
Remember
Reduce free radicals by not smoking, avoiding too much sun, and cutting down on repeatedly-fried food.