Antioxidants: What Are They and Why Do We Need Them?

Anti-cancer, anti-aging, anti-dementia – with health claims like these, it’s no wonder people are looking for ways to increase antioxidant intake from the foods they eat to their skin care routines.

But what exactly are antioxidants? And what can we do to harness the power of these mighty compounds?

“Antioxidant” is basically an umbrella term that encompasses different substances that help maintain cell health and neutralize or limit damage caused by free radicals, which are compounds that attack healthy cells and can lead to DNA damage.

“Free radicals are implicated in cancer and a number of conditions, including heart disease,” says Dr. Donald Hensrud, an associate professor of nutrition and preventive medicine at Mayo Clinic and editor of The Mayo Clinic Diet.

There are hundreds of antioxidants that have been identified by scientists so far. Some of the best-known and most-studied types are:

As you can see, some vitamins and minerals also play an antioxidant role in the body, which can be confusing. Antioxidants are compounds that prevent or diffuse the damaging effects of free radicals. Vitamins A, C, and E can react with certain free radicals and prevent them from harming your cells. Minerals, such as zinc, form the active sites of antioxidant enzymes in the body – and these enzymes can remove free radicals before they can cause damage.

“Vitamins and minerals are often considered superior antioxidants because they can work in tandem with the body’s defense systems and can often be restored after they act to protect cells, unlike compounds from plants, which are lost,” says Alexander Michels, research associate with the Linus Pauling Institute at Oregon State University in Corvallis, Oregon.

Your body naturally produces some antioxidants to counteract the effects of free radicals, but the foods you eat play a big role in giving your body the ammunition it needs to counteract potential damage. Diet and nutrition experts frequently encourage eating a “rainbow” of colorful foods for optimal health – and no, they don’t mean M&Ms or Skittles.

“Many of the antioxidants themselves are the plant pigments that make them such bright colors,” says Dr. Michael Greger, founder of NutritionFacts.org and a member of the U.S. News Best Diets expert panel. “The same biochemical property that gives them those beautiful colors is actually the same property that allows them to detox free radicals.”

You can see for yourself which foods are richest in pigment, Greger says, like the difference between white and sweet potatoes. Red cabbage has more pigment than regular cabbage, red onions have more than white onions, purple grapes are better than green grapes and so forth. Even black sesame seeds are richer in antioxidants compared to the regular version, he says.

However, pigmentation alone is only part of the picture, at least when it comes to certain vegetables, like cauliflower and potatoes. Several studies and reviews support the rich antioxidant benefits of white potatoes. White potatoes exceed sweet potatoes in total antioxidant content and contribute a significant portion of specific antioxidants in the flavonoid, phenolic acid and carotenoid types, evidence shows.

There is much we do not know yet about how the various properties in foods work together. Different antioxidants have unique properties and chemical makeup meaning they play different roles and have different health benefits. For example, eating or taking a supplement with a high level of vitamin C and calling it a day will not have the health benefits that eating a wide variety of foods of various colors and nutritional content that includes vitamin C will.

In a way, antioxidants function together as a team – so focusing on a single or a few antioxidants alone may be counterproductive. They also work with other properties in food like phytochemicals, which are various biologically active compounds found in plants.

“Antioxidants work in concert,” Greger says. “Supplements might have a few antioxidants, whereas our bodies rely on hundreds of them – all working together to create this network to help our bodies dispose of free radicals. And high doses of a single antioxidant can upset this delicate balance. So, the whole food may be greater than the sum of its parts, creating a kind of synergistic reaction. That’s why we should try to get our antioxidants the way nature intended – and that’s from real food.”

“In the past, we used a reductionist approach to nutrition: ‘What’s the one nutrient that’s beneficial or one food that’s beneficial?’” Hensrud says. “As in: ‘Blueberries are the best source of antioxidants so how many blueberries should I eat?’”

Instead, he prefers to talk to his patients in practical, pragmatic terms.

“The bulk of the evidence supports a diet of minimally processed foods and mostly plants,” Hensrud says. “It sounds deceptively simple, but that’s what’s most important.”

Here are examples of foods with relatively high antioxidant content (measured by millimoles per 100 grams):

The big takeaway: Plant foods have 64 times more antioxidants than animal foods, on average, according to Greger. In particular, berries have about 10 times as much as other fruits and vegetables and are only beaten out by herbs and spices in their antioxidant proportions.

Being mindful of your antioxidant intake is a great way of maintaining your overall health and promoting your longevity. A review study published in the journal Advances in Nutrition evaluated results from 41 studies involving more than 500,000 total participants. In 74,000 cases, they found an inverse association between death risk and overall dietary antioxidants or certain specific antioxidants, including carotenoids and vitamin C. This suggests a reduced risk in all-cause mortality with greater antioxidant intake.

Antioxidants may also play a role in reducing the risk of heart disease, cancer and age-related conditions like dementia and macular degeneration, according to a large body of research.

Teasing out antioxidants’ prevention power is challenging in one way.
“Total antioxidant capacity in a diet correlates with lower risk of getting cancer, lower risk of dying from cancer and lower risk of dying prematurely altogether,” Greger says. “The problem, of course, is that high-antioxidant foods are among the healthiest foods, so there are all sorts of wonderful things found in these foods. How do we really know it’s the antioxidants?”

The bottom line is: If you focus on diverse, healthy, plant-based foods, you’ll reap benefits from antioxidants along with other key substances.

“There is not enough scientific evidence to suggest one group of phytochemicals-antioxidants versus another, so it would be best to work on the foods with dense amounts of phytochemicals-antioxidants in general. Focusing on the darkest colors of fruits and vegetables (greens, reds, and purples, for example) is a good way to get more of the compounds that are beneficial,” Michels says.

Antioxidant supplements may be ineffective and, in some cases, harmful.

“Antioxidant supplements are a multibillion-dollar industry, touted for anti-aging properties, but we have hundreds of studies to the contrary,” Greger says.

However, an antioxidant ‘cocktail’ has been found beneficial for some patients with age-related macular degeneration, a progressive eye disease.

Building on our knowledge of healthy antioxidant properties in food, there was a wave of studies on antioxidant supplements. One study conducted in part by the National Cancer Institute followed 30,000 male smokers in Finland to determine whether specific supplements prevented lung and other cancers. No prevention benefit was seen from either supplement, and there may have even been unintended negative effects of supplementation.

“Unexpectedly, we observed a higher incidence of lung cancer among the men who received beta-carotene than those who did not,” researchers reported.

A different study published in JAMA followed nearly 40,000 healthy women to determine if vitamin E supplementation decreases risk of cardiovascular disease and cancer. Researchers found no overall preventive benefit for major cardiovascular events including heart attacks, stroke or cardiovascular death, no overall cancer benefit or effect on total mortality in women taking vitamin E. The data did not support vitamin E supplementation for preventing cardiovascular disease or cancer among healthy women.

Many antioxidant supplementation studies have not shown to confer health benefits, which may be because many antioxidants work best in tandem with other nutrients, plant chemicals (polyphenols) and even other antioxidants. Also, there are differences in types and amounts of antioxidants found in food versus supplements. For example, vitamin E supplements typically come in one form, alpha-tocopherol, whereas in food there are eight different forms of it.

When considering a supplement, keep in mind the supplement industry is not regulated by the Food and Drug Administration. Therefore, ingredients may not be as advertised, and the suggested dose may be too high to be healthy or too low to be effective. Speak to your doctor to find out if a particular supplement and dosage may be right for you.

On the flip side of antioxidants, certain foods are higher in harmful substances – known as pro-oxidants – that can actually contribute to unhealthy oxidative stress. While they may confer some health benefits, it’s important to counterbalance them with antioxidant-rich foods.

Try to be aware of your consumption and limit these pro-oxidant foods:

“Sugar is a pro-oxidant,” Greger says. “Drink a soda and you’re going to decrease the total antioxidant content of your bloodstream. However, interestingly, if you drink the same amount of sugar in the form of orange juice, you don’t get the spike on oxidation. Why? Because the sugar in food is part of a package deal, with antioxidants like vitamin C – just like nature intended.”

So, rather than spooning sugar in your coffee or eating frosting-rich cake, satisfy your sweet tooth with some fruit.

If you have a meal like a bagel with cream cheese, adding strawberries for dessert can neutralize free radical damage.

“Otherwise, by lunchtime, you’re already in oxidative debt,” Greger says. “You’ve used up antioxidants and dug your hole deeper.”

Ultimately, it’s important to stay mindful of what you eat.

“Every meal … is an opportunity to tip the balance from a pro-oxidant to an antioxidant direction,” Greger says.