Antioxidants

What Are They and How DoThey Work

Hardly a week goes by without news of antioxidants' health-promoting benefits. Experts believe these nutritional substances may help prevent heart disease, fight certain cancers, ward off dementia, and even slow certain aging processes.Understanding the benefits of the different things we eat is crucial to maintaining a balanced diet.

Antioxidants are compounds found in plants that provide the ability to prevent damage caused by oxidation during our metabolic processes.There are thousands of antioxidants found in fruits, vegetables, whole grains, nuts, legumes, meats, poultry, and fish. Even foods once not known for being especially healthful, such as chocolate, coffee, and red wine, are now recognized as providers of powerful antioxidants.

However, the growing number of antioxidants being discovered (so far, there are more than 4,000 known flavonoids, and that's only one class of antioxidant) and the continual discoveries of new antioxidant food sources cloud understanding of these substances.

What Are Antioxidants?

We need oxygen to live. It travels from the lungs to every corner of the body, helping cells metabolize food into energy. But oxygen has a downside. Normally, the molecules in our cells have a full set of electrons, which keep them stable (think of them as a fortress surrounding a castle). But when these molecules come into contact with oxygen (i.e., they are "oxidized") they lose an electron, converting to an unstable type of molecule known as a free radical.

"Free radicals, if not neutralized, damage cells, proteins, fats and cellular DNA.

Ingeniously, Antioxidants disable free radicals by donating electrons to replace those lost during oxidation. Some antioxidants can be manufactured by your body; others must be obtained from food. Dietary antioxidants fall into two groups. The first is made up of certain familiar vitamins and minerals, like vitamins C and E, selenium, and zinc that have antioxidant capabilities. The second consists of the thousands of organic compounds found in plant foods that have functions like giving grapes their purple skins or cabbages their slightly sulfurous odor. They have names like anthocyanidins, catechins, lutein, quercetin, and resveratrol.

Preventing oxidation may have earned antioxidants their name, but we now know these substances do more than disable free radicals. Antioxidants also help reduce inflammation, keep arteries flexible, and preserve the genetic material every cell contains to prevent mutation. Each antioxidant also offers unique perks. For example, flavonoids in berries may help improve artery health, while lutein in spinach may help protect your vision by preventing macular degeneration.

Antioxidant Food Sources

To measure a food's antioxidant content, scientists test it in a lab, where they usually measure equal quantities of each food they test. However, that amount may not be close to the serving size we usually eat. Realizing this, many-but not all-researchers convert their findings to common portion sizes before publishing the results of their work. That's one reason why Monday's health news may place blueberries on top of the antioxidant heap, while Thursday's may claim broccoli contains the highest levels of the compounds. In addition the ORAC score can change depending on the time of harvest, the soil nutrient content it grown in and the stress the plant was exposed to.

Also, several kinds of tests are used to measure a food's antioxidant power, another reason for the multiplicity of findings. The most popular test is Oxygen Radical Absorbance Capacity (ORAC). ORAC measures an antioxidant's ability to protect against the most common free radical in human plasma, the peroxyl radical.

ORAC is a helpful starting point to guide consumers to foods that are rich in antioxidants as part of a diet that contains many different antioxidant-rich foods, especially since new antioxidants are being discovered all the time.

Anthocyanidin-rich blueberries are a good example. They may be antioxidant powerhouses in a test tube, but we don't absorb their antioxidants well and their effectiveness in our bodies is short lived. To gain the full benefit, you'd likely need to eat more of them than foods with a lower ORAC score that contain more readily absorbable antioxidants, such as kiwifruit or grapes.

What's more, antioxidant levels vary among different samples of the same food. For example, all apples don't have the same amount of quercetin and all lettuces don't provide the same dose of lutein.

Eating for optimal nutrition

When it comes to dietary antioxidants, variety and timing are the key points.

Experts agree-while there's no formal recommendation for the amount of antioxidants we need-the best way to obtain them is from a varied diet.  Antioxidants work synergistically and may provide a greater benefit together than they do individually. Consider a recent European Journal of Clinical Nutrition study that found the total antioxidants in a person's diet had a more substantial impact on plasma beta-carotene levels than the amount of beta-carotene in a person's diet. Researchers surmise other antioxidants pitch in to "spare" beta-carotene so it can work harder when it's needed. The same is true for other antioxidant vitamins. By consuming antioxidant-rich foods, you end up protecting or recycling compounds like vitamins C and E, increasing their levels so they're more available to function.

Unlike many other nutrients, you can't store antioxidants, so you have to keep replenishing the supply. "The important thing is getting antioxidants throughout the day and keeping levels high because they go down very quickly," Vinson says. Even small amounts can provide significant benefits. When German researchers recently looked at the impact of small amounts of polyphenols in dark chocolate on blood pressure, they found that just 0.2 ounces of dark chocolate shaved three systolic points and two diastolic points off hypertensive subjects' blood pressure.

Should You Supplement?

As a Nutritionist I will first tell you that supplements are not substitutes for a healthy diet. Many people think they can take a few antioxidant supplements and then eat anything they want and still gain health. It just doesn't work that way.  Depending on the latest antioxidant in the news I get asked about just taking that antioxidant. When you eat a variety of vegetables and fruits you get thousands of nutrient compounds including hundreds of antioxidants. With that being said because of the stress we are under and the nutrient depletion of our foods I strongly recommend a "whole food core health supplement" this means the nutrients are coming from the foods they are found in and not as an isolated nutrient. "You need to have diversity in your diet, and there is no pill that provides it all."

 

The astounding array ofantioxidants

Although there are thousands of known antioxidant compounds, scientists speculate that many antioxidants are as yet undiscovered, others are increasingly well known. Listed below are antioxidants you may have read about; they're categorized by family of associated compounds and listed with some of their most common food sources.

Carotenoids

Beta-carotene: Orange/yellow fruits and vegetables (carrots, cantaloupe); dark leafy greens (spinach, kale)

Lycopene: Red-fleshed fruits and vegetables (watermelon, tomato)

Lutein/Zeaxanthin: Romaine lettuce, dark leafy greens, citrus fruits, corn, egg yolks

Flavonoids

Anthocyanidins: Berries, grapes, wine

Catechins: Tea, cocoa

Flavonols: Tea, cocoa, coffee, berries, grapes, apples, wine

Flavonones: Citrus fruits

Isoflavones/Phytoestrogens: Soybeans, whole wheat, flaxseed

Quercetin: Apples, tea, capers, citrus fruits

Organosulfurs: Cabbages, Brussels sprouts, cauliflower

Selenium: Brazil nuts, red meat, tuna

Sulfides: Onions, garlic, leeks, chives

Vitamin C: Citrus fruits, bell peppers, broccoli, kiwifruit

Vitamin E (tocopherols): Wheat germ, mono-unsaturated oils (sunflower oil, safflower oil), tree nuts (almonds, hazelnuts), peanuts