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Antioxidants: what they are, why you need them, and where to find them

Antioxidants have built a reputation as dietary powerhouses that provide strong health benefits. It’s antioxidants that have made news stories describe blueberries as a “superfood,” boosted the health benefits of green tea, and even given us hope that wine and chocolate might be part of a balanced diet. A look behind the hype can help clarify what antioxidants are, what they do, and how they can enhance health.

Antioxidants are naturally occurring substances found in certain foods, says Carolyn Christo, a registered dietitian with TRIDEC, the diabetes management program at Women’s College Hospital. They take several forms: some antioxidants are vitamins (such as vitamin A and vitamin C), some are minerals and some are phytochemicals (chemicals found naturally in plants).

Fighting radicals

Factors such as an unhealthy diet, exposure to pollution, smoking, stress and aging can create unstable molecules called free radicals, which cause “oxidative damage” to our body’s cells. Antioxidants help prevent cell damage by fighting  or “stabilizing” free radicals.

Dietitians of Canada compares the process to a car that might rust:

“It can rust when the metal in the car reacts with oxygen. If you cover it with a protective coating, it does not rust as quickly,” the organization’s website explains. “For our bodies, antioxidants are that protective coating. They protect your body’s cells from damage caused by pollutants, smoke, unhealthy diets and the normal aging process.”

Researchers believe that’s how antioxidants may contribute to good health, and help prevent conditions that may be linked to oxidative stress, such as heart disease and cancer.

Types of antioxidants, and where to find them

Several vitamins – including vitamins C, E and A – are antioxidants.

Vitamin C            citrus fruits, bell peppers, broccoli, strawberries, tomatoes

Vitamin E            nuts, seeds, whole grains, green leafy vegetables, vegetable oils

Vitamin A            carrots, squash, broccoli, sweet potato, tomatoes, cantaloupe, dark leafy greens

Many phytochemicals behave as antioxidants. Christo notes that there are more than 1,000 known phytochemicals, and researchers continue to discover more. These are not nutrients, but compounds that plants produce to protect themselves from things like fungi, bacteria and cellular damage. When we eat them, they can help keep us healthy, too. Antioxidant phytochemicals fall under four main subgroups:

Carotenoids       carrots, leafy greens, citrus fruits, tomatoes

Flavonoids          berries, cherries, green tea, black tea, red grapes, citrus fruits, apples, cocoa, chocolate, broccoli, cranberries, wine, peanuts, cinnamon

Indoles                 broccoli, cauliflower, cabbage

Sulphides            garlic, onions, leeks, scallions, broccoli, cabbage

Some minerals are also antioxidants:

Selenium            nuts, whole grains, meat, poultry, seafood, sunflower seeds

Zinc                      dairy products, meat, fish, poultry, beans

Can a food be “super”?

Because they are believed to have health benefits, antioxidants are often in the news. For example, you may have read about “superfoods,” or that wine and chocolate may have health benefits due to their antioxidant properties.

“’Superfood’ is a media term, not a scientific term,” Christo says. That’s why there are different lists of superfoods from different sources and at different times. But in general, they’re foods that can have a positive impact on health.

Examples of antioxidant- and phytochemical-rich foods that are often promoted as superfoods include berries, leafy greens such as kale and spinach, nuts, broccoli, tomatoes, garlic, green tea and salmon.

Whether or not you assign them “super” status, these foods definitely have a place in a healthy diet.

“You don’t need to eat them every day, but incorporate them on a regular basis,” says Christo.

So is chocolate a health food?

As for the wine and chocolate, there may be a place for them in a balanced diet.

“Dark chocolate has a high amount of flavonoids,” Christo says. “Research supports that because of the flavonoids, it might have a positive effect on heart health.”

That doesn’t mean all chocolate is good for you. Choose dark chocolate, with at least 70 per cent cocoa solids, Christo says. She also notes that it’s important to limit the amounts you eat because, of course, there’s a catch.

“It’s high in fat,” she says. Too much fat has negative health effects. “Eating it freely in large portions might cancel out the positive effects.”

Wine is similar: the right type can have benefits, but moderation is key.

Red wine contains the antioxidants resveratrol, quercetin and catechins. Christo explains that animal studies have linked these antioxidants to reduced inflammation of blood vessels, which may reduce risk for heart disease.

“As with any type of alcohol, moderation matters,” she says. “Too much can increase your risk of other health issues.” That means alcohol should be limited to one drink per day for women and two drinks per day for men.

A balanced approach

The chocolate and wine examples illustrate the importance of balance, and of interpreting nutrition research carefully. Current research suggests that antioxidants are associated with reduced risk of chronic conditions, but there are no definitive results showing that eating specific foods will ward off disease. What research has shown consistently is that certain eating habits are linked with health benefits.

“A dietary pattern that is high in fruits and vegetables and other plant foods is associated with a lower risk of disease,” Christo says. While those foods are rich in antioxidants, it may not be the antioxidants that are providing those benefits. It might be other factors, such as what’s NOT present in that dietary pattern.

“It could be that people who eat more fruits and vegetables and other natural plant foods are eating less unhealthy, damaging foods,” Christo explains. “One of the biggest benefits of eating lots of fruits and vegetables and other plant-based foods is that it means you’re not eating lots of brownies, candies, ice cream and chips.”

Regardless of where the benefits are coming from, enjoying antioxidant-rich foods such as whole grains, broccoli, citrus fruits, berries and other foods rich in vitamins and phytochemicals is an important component of a dietary pattern with proven health benefits.



This information is provided by Women’s College Hospital and is not intended to replace the medical advice of your doctor or healthcare provider. Please consult your healthcare provider for advice about a specific medical condition. This document was last reviewed on: April 12, 2012

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