Antioxidants

Overview

In order to understand what an antioxidant is, it helps to know what oxidation is.

At its most basic level, oxidation is the loss of electrons. And when a compound loses electrons, its properties change.

Let’s take some real-life examples:

An un-oxidized iron nail will be strong and have a dark silvery grey color. However, once it begins to oxidize, it will change color and begin to lose its structure, eventually turning to a reddish-brown powder. This all happens due to oxidation. In food, we can see oxidation in process when a fruit begins to brown. When you cut an apple, the flesh inside will start to turn brown very quickly due to a loss in electrons. Similarly, a rusting car is an oxidation process, as is digestion, as is exercise.

Oxidation causes the production of free radicals, which are unstable compounds that can cause damage, including cell or tissue damage. It is thought that this damage underlies the cause of many chronic diseases such as diabetes, cancer, cardiovascular disease, and others. It’s not that oxidation is bad, it’s just that when it’s rampantly unmanaged, it can be destructive.

Antioxidants are therefore (can you guess?) anti-oxidation. Antioxidants inhibit the oxidation process by “giving electrons”, thereby neutralizing free radical damage. Using one of the examples above, if you slice an apple then dust it with some powdered vitamin C (an antioxidant), the apple will resist browning.

The main categories of dietary antioxidants include vitamin A, vitamin C, vitamin E, carotenoids, and phenols. While selenium, zinc, manganese, and some other nutrients are often referred to as antioxidants, they don’t actually have antioxidant potential themselves, but rather act as co-factors in the antioxidant activity of other compounds.

Although antioxidants can include industrial chemicals as well as chemicals produced in the body, this entry concerns dietary antioxidants, which are the antioxidants that naturally occur in whole foods.

Importance

Oxidation is always occurring in the body. It is a natural by-product of digestion, exercise, excessive sun exposure, and the aging process. Oxidation can also be induced by exposure to toxins such as alcohol, cigarette smoke, and environmental pollutants.

Due to their ability to offset the oxidation process, dietary antioxidants ensure that we age well, resist disease, and recover properly, whether from exercise, an infection, a sunburn, or a scraped knee.

Because oxidation is always occurring, our need for antioxidants is ongoing. Luckily, antioxidants are abundant in whole foods, particularly in colorful plants. So as long as we keep eating a diet rich in antioxidants (read: plates covered in colorful plants), we can keep oxidation in check.

Food Sources

As mentioned, the best sources of antioxidants are found in colorful plants. Generally, the deeper pigmented the plant is, the more antioxidants it will have. For example, purple cabbage will have more antioxidants than regular cabbage, which is pale green.

Although there is a lot of overlap, certain foods are better sources than others for specific antioxidants.

Vitamin A

• Can come in the form of retinol from animal sources, or can be synthesized from beta-carotene from plants
• Fat-soluble
• Good sources: Animal liver and cod liver oil; dark green, yellow, orange, or coral-colored plants (e.g. kale, collard greens, carrots, squash, mangos, oranges, goji berries, apricots, watermelon)

Vitamin C

• Very heat sensitive so only present in raw or very lightly cooked plants
• Water-soluble
• Good sources: (raw) Red pepper, citrus fruits, leafy greens, berries (especially acerola cherries and a rare Amazonian berry called camu camu)

Vitamin E

• Includes eight different compounds: four tocopherols (alpha, beta, delta, gamma) and four tocotrienols (alpha, beta, delta, gamma)
• Fat-soluble
• Good sources: Nuts, seeds, whole grains (particularly the germ portion, such as wheat germ), leafy greens

Carotenoids

• Includes a number of compounds: alpha-carotene, astaxanthin, beta-carotene, canthaxanthin, lutein, lycopene, zeaxanthin
• Good sources: Dark leafy greens, spirulina, tomatoes, guava, goji berries, salmon, squash, carrots, sweet potatoes

Phenols

• Phenols, sometimes referred to as phenolic compounds, are a class of chemicals produced by plants. (They can also be produced synthetically or by microorganisms, but this article concerns the dietary variety which come from whole foods.) Although they are not considered essential nutrients, they do benefit health due to their antioxidant properties.
• Good sources: Green tea, black tea, cocoa, red wine, berries, herbs / spices (e.g. turmeric, clove, oregano), vegetables, coffee, olives, extra virgin olive oil.

Deficiencies

While a person can become clinically deficient in the antioxidant vitamins [vitamin A (which includes carotenoids), vitamin C, and vitamin E], phenols are not considered essential so therefore deficiencies in them are not recognized.

A deficiency in either vitamin A, vitamin C, or vitamin E will manifest in unique symptoms (see the entry for the specific vitamin for more details), but a general lack of antioxidants in the diet may not exhibit such predictable patterns.

However, it is recognized that a lack of dietary antioxidants makes an individual more vulnerable to oxidative stress (unmanaged oxidation in the body), which is thought to underlie many disease processes.

It is still unclear what role supplements play in the management of oxidation. A good diet rich in antioxidants, however, is indisputably crucial for good health.

The best tip for “getting enough”? Turn your plate into a rainbow of colorful whole foods at every meal.

Excess/Toxicity

It is likely nearly impossible to get an excess of antioxidants through food alone. However, as mentioned, it is unclear what role supplements play in the management of oxidation.

Although they are thought of as “bad guys” by the masses, free radicals do actually serve a purpose in the body and oxidation should occur as a natural and healthy part of human metabolism.

Managing oxidation is about balance, not about making it go away completely, so before you start taking antioxidant supplements with abandon, thinking “more is better”, make sure you know what you’re doing.

Try a bowl of blueberries instead.

Recipe

For a recipe rich in antioxidants, check out the entries for any of the food sources mentioned in this entry.

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Related Foods

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  Phytochemicals
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  Zinc
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  Sodium
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  Selenium