Atoms are made up of protons and electrons - the number of protons (positively + charged) dictate the number of electrons (negatively - charged). Atoms are programmed to find stability with equal number of both by gaining or losing electrons, or bonding with other atoms to share their electrons. This is how molecules are formed.
Where, for example through UV damage, a proton is unpaired the atom becomes an unstable Free Radical (FR) attacking other molecules to seize the electron they need to stabilise. The attacked molecules then becomes a FR itself, causing a chain reaction that eventually harms living cells, causing ageing. Oxygen atom FRs are particularly virulent, which is where the term oxidative stress comes from.
Anti-oxidants are key to preventing cellular damage because they can donate electrons without becoming 'radicalised' themselves, therefore breaking the chain. Our cells have a natural defense system called superoxide dismutase (SOD), but it's sod's law that this degenerates with age, so as our cells are becoming less efficient they are also less protected. This is why anti-oxidants are important to delay ageing and give you the best chance to fight ill-health.
The best way to combat Free Radicals is to protect yourself from the sun and pollution, eat lots of leafy greens and purple fruit and veg, avoid alcohol, smoking, polluted environments and errr oxygen...
If life tends to get in the way of daily juicing, yoga on mountaintops and drinking hourly from glacial springs, try a two-pronged attack using both ingestible and topical anti-oxidants. look for Vitamins C & E, Alpha & Beta Carotenes, Resveratrol, Niacinamide, Lycopene, Polyphenols and Bioflavenoids. Altrient C gel is a brilliant source of Vitamin C, so bio-available that they guarantee 98% absorption (vit C supplements can be as inefficient as 30% absorption) as are the Strong Nutrients Cellution pills, which are designed to encourage flourishing cell rejuvenation and overall youthful efficiency.