FRIDAY, Feb. 23, 2018 (HealthDay News) -- Antioxidants -- it's a hot nutrition buzzword, but do you know what they really are?

Antioxidants are naturally occurring chemicals that block the activity of other chemicals called free radicals. Free radicals are formed naturally in the body and actually play an important role in many everyday processes, such as exercise and metabolism. But at high concentrations, they can be hazardous to your health, with the potential to cause cell damage that could lead to cancer.

Your body makes some needed antioxidants to battle free radicals, and you can get others through a healthy diet, notably from richly colored fruits and vegetables.

Well-known dietary antioxidants and their sources include:

• Beta-carotene: carrots, squashes, sweet potatoes.
• Lycopene: pink grapefruit, tomatoes (cooked), watermelon.
• Lutein: most leafy green vegetables.
• Selenium: grains, protein sources, nuts, legumes.
• Vitamin A: butter, eggs, milk, liver.
• Vitamin C: berries, oranges and other citrus, cantaloupe, bell peppers, broccoli, kale, papaya, tomatoes.
• Vitamin E: almonds, hazelnuts, other nuts and seeds and their oils.

There are actually hundreds of antioxidants. Many are categorized as phenols, polyphenols and flavonoids. And unlike vitamins, it's not possible to capture them all in a supplement, so boosting the quality of your diet is a must.

Berries have some of the highest antioxidant levels of any fresh fruit. Kale and spinach are the top vegetable sources. Eating a wide variety of produce can bring many different health benefits. For instance, eating oranges and grapefruits might lower your stroke risk because of their flavonoids, just one type of antioxidant in these fruits.

The different colors of fruits and vegetables reflect their nutrient makeup. That's why the advice to "eat a rainbow" is a best bet.

More information

The American Academy of Family Physicians details the most important antioxidants and their best food sources.