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Antioxidants, Super Nutrients: Why they are Good for Your Health and Where to Find Them in Your Diet

by Roy Stevenson(more info)

listed in antioxidants, originally published in issue 166 - January 2010

Oxygen – you need to know two things about this gas. The first thing is, as aerobic animals, we need oxygen to survive. The second is that, ironically, it contributes to human ageing and illness.

How can the very gas that supports life contribute to the end of life? It goes like this. When we metabolize oxygen, nasty little by-products known as free radicals form through a process called oxidation, (when molecules lose an electron from their outer shell).

Vegetables

The free radicals, now with an unpaired electron in their outer shell, seek out other nearby molecules with complete electron pairings, to try to steal one of them-a sort of internal chain reaction.

The free radicals rampage through our cells disrupting other molecules, damaging their internal structure and impairing their function, which in turn contributes to ageing and other health problems and diseases.

Oxidative stress damages proteins, lipids, and carbohydrates, even DNA. Also implicated in diseases like cancer, cardiovascular disease, Alzheimer's disease, Parkinson's Disease, immune dysfunction, cataracts and macular degeneration, we suspect this is just the tip of the iceberg of free radical malfeasance iceberg.

Free radicals present a problem for fitness buffs too, because when we exercise, enormous numbers of free radicals form because we process copious amounts of oxygen. This translates into increased post-exercise muscle damage and inflammation, and a myriad of other less than desirable effects.

Antioxidants 101

However, all is not lost in this never-ending battle against rampaging free radicals. Antioxidants, produced naturally in the body, or obtained from our food, deal with most free radicals by blocking this reaction. They stabilize free radicals before they can react and can cause harm by donating electrons to replace those lost during the oxidation process, hence their name. Antioxidant reactions occur about 2,000 times per second in our body under normal circumstances, and many multiples of this during aerobic exercise.

The overall benefits of antioxidants seem like the holy grail of medical panaceas: reduction in inflammation, healthier arteries, reduced macular degeneration, and less damage to genetic materials in the cells, to name a few.

However, the body's antioxidant defences do not block 100% of the free radical activity, and antioxidants do not store well in our body, so we must keep replenishing the supply, preferably throughout the day.

Studies and Guidelines for Antioxidants

Much research has looked at free radical production and the ensuing blocking of the chain reaction that takes place when we increase our antioxidant levels through diet and dietary supplements.

Some studies show promising results that could have major implications for our longevity and health, although questions still remain about how they work and the optimal levels of antioxidants for health benefits.

Currently no government guidelines exist for consumers on how many and what kind of antioxidants we should consume in our daily diet, because nutrition researchers have not arrived at a consensus on uniform antioxidant measurements and dosages. They're also not exactly sure how effective individual antioxidants are against certain conditions – how a food behaves in a test tube and how it behaves in our body, due to digestion, absorption and metabolism – could be two different things. Some antioxidants may be absorbed well and others hardly at all.

Researchers use a test called Oxygen Radical Absorbance Capacity (ORAC), to measure an antioxidant's ability to protect against the free radical peroxyl that is abundant in our bloodstream. This provides a starting point to guide consumers to antioxidant-rich foods.

Where Do We Find Antioxidants?

Most antioxidants are found in fruits and vegetables. The literature suggests that the combination of fruit and vegetables have synergistic effects on antioxidants, causing a reduction in cancer and heart disease.

So when your mother said, "eat your vegetables and you'll grow big and strong and won't get sick", she was dispensing good advice. Antioxidants are also found in whole grains, nuts, legumes, meats, poultry, and fish.

Nutritionists consider whole foods to be the best way to boost antioxidant levels, versus taking individual antioxidant/vitamin supplements. Whole foods have a wide variety of antioxidant substances and provide other important macronutrients such as vitamins, minerals and fibre.

Antioxidant
Common Food Sources Antioxidant Properties Dietary Reference Intake
Beta-Carotene Cantaloupe, orange fruits & vegetables (carrots, sweet potatoes), leafy green vegetables (broccoli, spinach) Reduces free radical production from exercise and protects against muscle cell damage from free radicals 2,500 IU daily (one large carrot)
Vitamin C Green leafy vegetables, green peppers, raw cabbage, citrus fruits and juices, cantaloupe, berries Reduces exercise-induced free radical damage, protects muscle tissue from damage Upper limit 2,000 mg/daily
Vitamin E Raw wheat germ, mixed nuts, seeds, sunflower seeds, fish liver oils, polyunsaturated vegetable oils Helps with cell respiration, scavenges for free radicals during exercise, protective effect against free radical muscle cell damage, helps with immune function and DNA repair Upper limit 1,000 mg daily
Selenium Whole grain cereals, egg yolk, milk, chicken, seafood, broccoli, garlic, onions, cereal bran, Brazil nuts, whole grain cereals, meats, tuna, plant foods Helps activate glutathione peroxidase enzyme, protective effect against cellular damage from free radicals 400 mcg daily
Copper Whole grains, shellfish, eggs, almonds, leafy green vegetables, beans Helps produce antioxidant enzyme superoxide dismutase 10,000 mcg daily
Manganese Whole grains, egg yolks, dried peas and beans, leafy green vegetables Helps use superoxide dismutase Women 2.6 mg/daily; men 2.3
mg/daily
Table of Common Sources of Antioxidant Vitamins and Minerals
                                

Phytonutrients

There's more good news: fruits and vegetables contain thousands of organic compounds called phytonutrients, many of which act like super antioxidants. Their function is to protect the plant. In most cases, they're much more powerful than the antioxidant vitamins and minerals A, C, E and Selenium, and increase quality of life and possibly lifespan.

Types of Phytonutrients

The phytonutrient family has several siblings and offspring by the names of Carotenoids, Flavonoids, Isothiocyanates, Phenols, Sulfides, and many others. To give you some idea of how many phytonutrients exist, there are 4,000 flavonoids alone.

Benefits of Phytonutrients
  • Reducing cholesterol levels;
  • preventing cancers;
  • lowering blood pressure;
  • protecting against diabetes;
  • protecting eyes;
  • protecting cell differentiation;
  • regulating the immune system;
  • preventing tooth decay;
  • reducing blood clotting;
  • reducing inflammation;
  • and regulating hormones.
A list of the phytonutrient families and their major sources follows at the end of this article.

With this all in mind, what foods should we eat to keep our antioxidant levels topped up? Here are some antioxidant rich foods you should be including in your diet.

Fruits

Fruits are high in antioxidants, packed with vitamins, with lots of fibre. If you're eating from a selection of the following, you're getting adequate antioxidants: cranberries, red grapes, peaches, raspberries, strawberries, red currants, figs, cherries, pears, guava, oranges, apricots, mango, cantaloupe, watermelon, papaya, and tomatoes.

Dried Fruits

The antioxidant concentration is higher in dried fruits than in fresh – and they make excellent healthy snacks: try dried pears, plums, apples, peaches, figs, dates and raisins.

Vegetables

To boost your antioxidant stores eat: Broccoli, spinach, carrots, potatoes, artichokes, cabbage, asparagus, avocados, beetroot, radish, lettuce, sweet potatoes, squash, pumpkin, collard greens and kale.

Spices and Herbs

Many cooking spices are loaded with antioxidants: cinnamon, oregano, turmeric, cumin, parsley, basil, curry powder, mustard seed, ginger, pepper, chilli powder, paprika, garlic, coriander, onion and cardamom. Herbs with good quantities of antioxidants include sage, thyme, marjoram, tarragon, peppermint, oregano, savoury, and basil and dill weed.

Cereals and Nuts

Corn flakes, oatmeal and granola bars have antioxidants, and walnuts, hazelnuts, pistachio nuts, almonds, cashews, and macadamia nuts.

Beverages

Most antioxidants come from beverages in high concentrations that are very bioavailable and absorbed quickly. Fruit and vegetable juices such as apple juice, cider, tomato juice, pomegranate juice and pink grapefruit juice have many antioxidants.

Green and black tea have high levels of antioxidants. Coffee is also high in antioxidants, but should be consumed in moderation. However, adding milk to coffee or tea blocks antioxidants. Speaking of moderation, red wine and beer (if brewed from grains) provide a healthy dose.

Remember to eat a variety of fruits and vegetables of many colours. Foods with darker, richer colours like orange, yellow, blue, and red tend to be higher in antioxidants, so try to eat a variety of them.

How many fruit and vegetables should we be eating for some sort of protective effect against cancers, heart disease and other illnesses attributed to free radical damage?

The American Heart Association recommends that we "Eat a variety of fruit and vegetables. Choose 5 or more servings per day". Likewise, the American Cancer Society recommends we "Eat 5 or more servings of fruits and vegetables each day".

Class/Components Common Sources Potential Benefit
Carotenoids
Beta-carotene carrots, various fruits neutralizes free radicals which may damage cells; bolsters cellular antioxidant defences
Lutein, Zeaxanthin kale, collards, spinach, corn, eggs, citrus may contribute to maintenance of healthy vision
Lycopene tomatoes and processed tomato products may contribute to maintenance of prostate health
Flavonoids
Anthocyanidins berries, cherries, red grapes bolster cellular antioxidant defences; may contribute to maintenance of brain function
Flavanols-Catechins, Epicatechins, Procyanidins tea, cocoa, chocolate, apples, grapes may contribute to maintenance of heart health
Flavanones citrus foods neutralize free radicals which may damage cells; bolster cellular antioxidant defences
Flavonols onions, apples, tea, broccoli neutralize free radicals which may damage cells; bolster cellular antioxidant defences
Proanthocyanidins cranberries, cocoa, apples, strawberries, grapes, wine, peanuts, cinnamon may contribute to maintenance of urinary tract health and heart health
Isothiocyanates
Sulforaphane cauliflower, broccoli, sprouts, cabbage, kale, horseradish may enhance detoxification of undesirable compounds and bolster cellular antioxidant defences
Phenols
Caffeic acid, Ferulic acid apples, pears, citrus fruits, some vegetables may bolster cellular antioxidant defenses; may contribute to maintenance of healthy vision and heart health
Sulfides/Thiols
Diallyl sulfide, Allyl methyl trisulfide garlic, onions, leeks, scallions may enhance detoxification of undesirable compounds; may contribute to maintenance of heart health and healthy immune function
Dithiolthiones cruciferous vegetables-broccoli, cabbage, bok choy, collards contribute to maintenance of healthy immune function
Whole Grains
Whole grains
cereal grains may reduce risk of coronary heart disease and cancer; may contribute to reduced risk of diabetes
Chart adapted from International Food Information Council Foundation: Media Guide on Food Safety and Nutrition: 2004-2006.
Antioxidants: Classes, Sources and Benefits

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About Roy Stevenson

Roy Stevenson MSc has a Master's Degree in Exercise Physiology from Ohio University. He has taught Health and Nutrition at Highline Community College and Lake Washington Technical College for 18 years and currently teaches exercise science at Seattle University in Washington State. As a freelance writer, Roy has more than 200 articles on health, fitness, running, sports and triathlons published in over forty regional, national and international magazines in the USA, Canada, England, Scotland, Ireland, South Africa, Australia, and New Zealand. He may be contacted via roy_stevenson@hotmail.com

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