Our body has some beneficial uses for free radicals. They are atoms or molecules which are highly reactive because of an unpaired electron. They tend to balance themselves by stealing electrons from nearby atoms or molecules. Once they are balanced, the atom or molecule whose atom was stolen now becomes a free radical and just like the 'stealer', it will balance itself...and it goes on and on until an antioxidant quenches or scavenges the free radical by donating an electron without becoming reactive. That's the property of an antioxidant, it can donate an electron and not become unstable. There are instances when our body intentionally produces free radicals.
How our body uses free radicals
Our body's response to foreign invaders like bacteria and viruses is to mark them as 'foreign' which is done by the antibodies and then have them terminated by killer cells(leukocytes). One way for the killer cells to kill the foreign invaders is to encapsulate them and produce free radicals to terminate its existence. The process is called respiratory burst or oxidative burst. Free radical chain reaction occurs inside the encapsulation which eventually kills the cells of the foreign invaders.
That's how free radicals can be harmful to cells, it can kill or damage cells. In the case above, the body benefits from free radicals by terminating the existence of harmful foreign invaders in our body. On the other side of the coin, it was harmful for the foreign invaders.
The encapsulation for sure is also equipped with antioxidants to end the process because the encapsulation itself is composed of cells which are also subject to oxidative damage when the free radical chain reaction is left to do its thing. There are chances however that some free radicals can escape the encapsulation exposing other cells to probable oxidative damage. If there are antioxidants present outside the encapsulation, then there will be no problem.
Free radicals can really be beneficial for our body if it is intentionally produced by our body. If it was not intentionally generated to perform a specific task, then it would be harmful and antioxidants are needed to neutralize them. Free radical by products resulting from energy production in the mitochondria of our cells can also produce a chain reaction but if there are ample antioxidants nearby, the chain reaction would break before it can do damage to the cell.
We are constantly exposed to potential free radical chain reaction. Smoking, long exposure to sunlight, psychological or emotional stress, unhealthful eating habits are some free radical generators. If our body's supply of antioxidants fall short from the free radical generation, then its possible that it could do damage to our cells before the free radicals are 'quenched'.
Our body's supply of its own antioxidants like glutathione may not be adequate that's why eating fruits and vegetables could be very beneficial to us. It's not just the antioxidants contained in fruits and vegetables that our body can benefit, they are abundant in nutrients and vitamins that our bodies can surely utilize.
'Tis a holiday season and there are so much delicious food being served, some are good for the health and some may be not especially the sweets. Vegetables will likely be ignored in favor of those delicious looking preparations. Try to balance the quality of food you eat but don't overdo it. After all it's a holiday, a time for enjoyment! - there's always time to make up for it.