What are antioxidants? Food, free radicals, oxidative stress explained

You may have heard that antioxidants are an important part of your diet – but what are they and what do they do? Generally, antioxidants balance out something called oxidants or free radicals, which are potentially harmful molecules. Together, these molecules help stabilize the number of electrons that surround our atoms – the units that make up our cells.

Antioxidants play a role in a complex biochemical process, but don't worry, we will break it down into simple terms. We spoke with Dr. Gerardo Mackenzie, an associate professor in the Department of Nutrition at the University of California at Davis, to help walk us through one of the great marvels of our body.

To know what antioxidants are, we must first define free radicals.

Our cells are made of atoms. Atoms are surrounded by electrons. Atoms are stable when the electrons in the outer shell are in pairs. If the atom loses an electron, that atom will be unstable. To regain stability it will strip an electron from some other atom with which it comes in contact. This creates free radicals. These free radicals will take electrons from anywhere, even your own healthy cells, which can lead to damage. Free radicals are often associated with aging skin, cancer, dementia and other diseases.

Antioxidants can readily donate an electron to stabilize the free radical without becoming unstable itself. When antioxidants give up some of their own electrons to satisfy free radicals, they put the molecules back in balance.

When there isn't a sufficient amount of antioxidants to neutralize the free radicals, an imbalance called "oxidative stress" may occur.

Mackenzie defines oxidative stress as, "An imbalance or difference between reactive oxygen species being generated by our cells, through metabolic processes that occur in our cells, and the ability of our antioxidant defenses to interact and quench these reactive products."

Mackenzie explains free radicals play a normal, vital role in some cell processes.

While some low-level oxidative stress may be helpful, Mackenzie speculates that what most people think of when they talk about oxidative stress is likely the chronic, overload of oxidative stress. "This occurs when oxidative stress cannot be properly counteracted or detoxified by antioxidants. That can be a bigger problem." He adds, "When it's too much for our antioxidant defense systems, it can damage our cells. Oxidative stress can damage our cell's membranes, it can damage proteins, and it can also damage the DNA."

Antioxidants, the antidote for oxidative stress, can be found in our diet. Mackenzie says that vegetables and fruits are great sources of antioxidants. "The best-known antioxidants are vitamin C, vitamin E, selenium, carotenes, lycopene, etc., and they are found in many nuts, fresh fruits and vegetables." He recommends:

The old adage, "An apple a day keeps the doctor away" does have some truth. While antioxidants are not intended to treat any disease, they can help neutralize free radicals, which do appear to play a role in the development of certain diseases.

More about oxidative stress:What is oxidative stress? Everything you need to know.

What you should know about vitamins:Many people take daily vitamins. What they should know first.

What are dietary supplements?What are dietary supplements and how can they lead to better health?

What is the healthiest vegetable?There isn't one 'best,' but these are great nutrient-dense options.