What is an Antioxidant?
You may have heard about the health benefits of antioxidants, but do you know what an antioxidant is -- and how they actually work?
Antioxidants help fight oxidation, a normal chemical process that takes place in the body every day. It can be accelerated by stress, cigarette smoking, and alcohol. When there are disruptions in the natural oxidation process, highly unstable and potentially damaging molecules called free radicals are created. Oxygen triggers the formation of these destructive little chemicals, and, if left uncontrolled, they can cause damage to cells in the body. It's much like the chemical reaction that creates rust on a bicycle or turns the surface of a cut apple brown.
Simply put - Picture your body as a highway. Sometimes there are cracks and potholes in the road. Free radicals are like the cracks on the road and the antioxidants is the "stuff" used to fill those cracks to make the road normal again.
Antioxidants are our friends, they are dietary substances including some nutrients such as beta carotene, vitamins C and E and selenium, that can prevent damage to your body cells or repair damage that has been done.
Antioxidants are the knights in shining armour that subjugate the attack of free radicals in the body, the hazardous molecules that damage cells and procure aging and disease. Though antioxidants are produced naturally in the body, these decline with age, hence there is an increasing need to acquire them from the foods in our diet.
Antioxidants work by significantly slowing or preventing the oxidative
-- or damage from oxygen -- process caused by substances called free
radicals that can lead to cell dysfunction and the onset of problems like
heart disease and diabetes. Antioxidants may also improve the immune
function and perhaps lower your risk of infection and cancer. In your
body, the antioxidant process is similar to stopping an apple from
browning. Once you cut an apple, it begins to brown, but if you dip it in
orange juice, which contains vitamin C, it stays white.
From warding off heart disease to slowing degeneration of the brain and eyes, talk of the health benefits of antioxidants are quite common today. Antioxidants work by neutralizing highly reactive, destructive compounds called free radicals.
The Antioxidant Process
Antioxidants block the process of oxidation by neutralizing free radicals. In doing so, the antioxidants themselves become oxidized. That is why there is a constant need to replenish our antioxidant resources.
How they work can be classified in one of two ways:
Chain-breaking - When a free radical releases or steals an electron, a second radical is formed. This molecule then turns around and does the same thing to a third molecule, continuing to generate more unstable products. The process continues until termination occurs -- either the radical is stabilized by a chain-breaking antioxidant such as beta-carotene and vitamins C and E, or it simply decays into a harmless product.
Preventive - Antioxidant enzymes like superoxide dismutase, catalase and glutathione peroxidase prevent oxidation by reducing the rate of chain initiation. That is, by scavenging initiating radicals, such antioxidants can thwart an oxidation chain from ever setting in motion. They can also prevent oxidation by stabilizing transition metal radicals such as copper and iron.
The effectiveness of any given antioxidant in the body depends on which free radical is involved, how and where it is generated, and where the target of damage is. Thus, while in one particular system an antioxidant may protect against free radicals, in other systems it could have no effect at all. Or, in certain circumstances, an antioxidant may even act as a "pro-oxidant" that generates toxic oxygen species.
Free radicals are atoms or groups of atoms that contain an odd number of electrons. They can be formed when certain molecules interact with oxygen. Once formed, free radicals can start a chain of damaging chemical reactions. The biggest danger to the human body is their potential to react with cellular components like DNA or the cell membrane, causing cells to function poorly or die.
Free radicals are not only generated by the body, they are present in foods you eat as well as in the air you breathe. Some even come through exposure to sunlight that can harm the eyes and the skin. Free radicals can trap a low-density lipoprotein (LDL) in an artery wall and begin the formation of plaque; they can damage DNA; or they can change the course of what enters and leaves a cell. Any of these actions can be the start of a disease process.
Free radical production is actually a normal part of life, part of the equation of simply breathing in oxygen. Usually, the body's natural defence systems neutralize free radicals that develop, rendering them harmless. However, environmental assaults on the body, such as UV-radiation, pollutants and alcohol, can overpower the body's ability to neutralize free radicals, allowing them to cause damage to the structure and function of the body's cells. There is good evidence that this damage contributes to aging and leads to a host of illnesses, including cancer and heart disease.
Consuming more antioxidants helps provide the body with tools to neutralize harmful free radicals. It's estimated that there are more than 4,000 compounds in foods that act as antioxidants. The most studied include vitamins C and E, betacarotene and the mineral selenium.
Many people think "supplements" when they think about getting more antioxidants. The supplement aisle, however, is not the only place to find these important compounds. Better places include the produce section, the frozen fruit and vegetable section and the whole grains section of your supermarket. Why? Because the foods in these sections come packaged with other complementary nutrients and phytochemicals. They can provide better insurance than supplements that you're getting the antioxidants you need in the right amount and form.
The best way to get a variety of antioxidants in the diet is to eat foods that represent all the colours of the rainbow. Each colour provides its own unique antioxidant effects. Bright orange, deep yellow fruits and vegetables like carrots, sweet potatoes, and apricots provide one type of antioxidant. Red foods like tomatoes, provide another. Green vegetables, such as broccoli and cabbage, and blue or purple foods, like blueberries and eggplant, each have their own antioxidant packages. Curcumin, the substance that makes turmeric yellow, is also believed to offer benefits.
WHAT ANTIOXIDANTS CAN -- AND CAN'T -- DO Scientists began to theorize that free-radical damage was involved in the early stages of atherosclerosis and might play a role in the development of many other chronic medical conditions in the 1990s. Studies at the time suggested that people who ate few antioxidant-rich fruits and vegetables had a greater risk of developing these medical conditions. So began several clinical trials in which antioxidant supplements like beta carotene and vitamin E were tested for their protection against heart disease, cancer, and other conditions. As a result, "antioxidants" became a buzzword in the '90s, and their benefits were glorified by the media, by the the food industry who began labelling foods as "rich in antioxidants," and by the supplement industry as they began hyping the health benefits of antioxidant supplements. They were even promoted as anti-aging ingredients in beauty products.
IS THERE ANY HARM IN TAKING ANTIOXIDANT SUPPLEMENTS? Whether they are taken singularly or in combination concoctions, antioxidants could have adverse health effects, as the prostate cancer and lung cancer studies mentioned earlier suggest. Supplementation has also been linked to an increased risk of skin cancer in women. Another study indicated that those who took vitamin A, E, and beta carotene supplements may be at risk for premature death. Excessive intake of vitamin E has also been associated with heart failure and increased bleeding. The Food and Drug Administration does not regulate dietary supplements, and they can be sold with little or no research as to their safety, purity, and effectiveness. Dietary supplement manufacturing methods are not always standardized, so how well they work and their side effects can differ between brands or even within a brand. The form of a dietary supplement purchased in a drug store or health food store is likely not the same form used in research. The long-term effects of supplemental antioxidants are not known.
Important for the Eyes Perhaps the most promising area in antioxidant research is the area of eye health. A study found that a combination of the antioxidants beta carotene, vitamins C and E, and the mineral zinc reduced the risk of developing advanced stages of age-related macular degeneration (AMD) in those who had intermediate or advanced AMD in one eye.
The Bottom Line - Despite numerous studies, no substantial health benefits have been demonstrated for supplemental antioxidants. Antioxidants in food, however, are considered safe. Until there is more conclusive research, the best source of antioxidants is a diet rich in fruits, vegetables, and whole grains. Health organizations such as the American Heart Association, the American Cancer Society, and the American Institute for Cancer Research recommend getting antioxidants from food instead of supplements until research determines whether supplements are safe and provide the same benefits as antioxidants found naturally in food.
There is plenty of research that suggests that whole grains, fruits, and vegetables, all of which contain extensive networks of antioxidants, are beneficial to health. The best assurance of consuming adequate amounts of protective antioxidants is to eat between five and nine servings of fruits and vegetables representing all the colours of the rainbow every day. Snacking on small amounts of nuts and consuming wine in moderation also contribute to antioxidant consumption. To prevent the "biological rust" that oxidation and the stress of life can wreak on your cells, help them help themselves by choosing your foods wisely. Your cells need the variety of antioxidants provided by different foods to fight the destructive little molecules that wage war in the body on a daily basis.
Here are some good food sources of the most studied antioxidants.
Beta-carotene -- It is found in many foods that are orange in colour including, Carrots, squash, broccoli, sweet potatoes, tomatoes, kale, collards, cantaloupe, peaches and apricots. are particularly rich sources of beta-carotene. Beta carotene now has a separate page - here.
The most studied of more than 600 different carotenoids that have been discovered, beta-carotene protects dark green, yellow and orange vegetables and fruits from solar radiation damage. It is thought that it plays a similar role in the body.
Beta-carotene (C40 H56) is an orange pigment found in most fruits and vegetables. It was discovered by Heinrich Wilhelm Ferdinand Wackenroder in 1831 in the roots of carrots and named the substance "carotin." Wackenroder was an analytical chemist at the Pharmaceutical Institute in Jena, Germany (www.life.illinois.edu/govindjee/CarFin 1.html).
In 1907, Richard Willstater assigned the formula C40 H56 to carotin (http://lpi.oregonstate.edu/infocenter/phytochemicals/carotenoids/).
In 1831, beta-carotene was first isolated from the roots of carrots, but it was not until the Nobel prize-winning research of Paul Karrer in the early 1930s that the structure of the substance was determined. The earliest use of synthesized beta-carotene was as a food colorant, but during the 1980s the vitamin precursor’s growing reputation as an antioxidant and a possible cancer-fighter resulted in its frequent inclusion in vitamin supplements. Since that time, however, conflicting findings about the benefits of taking synthesized beta-carotene have surfaced.
Tests have shown that three percent of the total beta-carotene content is released from raw carrots when consumed in raw pieces. When homogenized (pulped) 21% was released. Cooking the pulp increased the accessibility to 27%. Addition of cooking oil to the cooked pulp further increased the released amount to 39%. (European Journal of Clinical Nutrition (2002) 56, 425–430- Estimation of carotenoid accessibility from carrots determined by an in vitro digestion method, Hedren et al)
Vitamin C -- Important sources include citrus fruits, green peppers, broccoli, green leafy vegetables, strawberries, raw cabbage and potatoes. It is also found in cereals, beef, poultry and fish.
Also called ascorbic acid, vitamin C is a water-soluble vitamin found in all body fluids, so it may be one of our first lines of defence. This powerful antioxidant cannot be stored by the body, so it's important to get some regularly -- not a difficult task if you eat fruits and vegetables.
Vitamin E -- Important sources include wheat germ, nuts (almonds), seeds, whole grains, green leafy vegetables, broccoli, mangos corn and soybean oil and fish-liver oil.
A fat-soluble vitamin also known as alpha-tocopherol, it can be stored with fat in the liver and other tissues, vitamin E is promoted for a range of purposes -- from delaying aging to healing sunburn. While it's not a miracle worker, it's another powerful antioxidant.
Selenium -- Good food sources include fish, shellfish, red meat, grains, eggs, chicken and garlic.
Selenium is a mineral, not an antioxidant nutrient. However, it is a component of antioxidant enzymes. This mineral is thought to help fight cell damage by oxygen-derived compounds and thus may help protect against cancer. It is best to get selenium through foods, as large doses of the supplement form can be toxic. Vegetables can also be a good source if grown in selenium-rich soils. The amount of selenium in soil, which varies by region, determines the amount of selenium in the foods grown in that soil. Animals that eat grains or plants grown in selenium-rich soil have higher levels of selenium in their muscle. In the United States, meats and bread are common sources of dietary selenium. Brazil nuts also contain large quantities of selenium.
Lutein, best known for its association with healthy eyes, is abundant in green, leafy vegetables such as collard greens, spinach, and kale.
Lycopene is a potent antioxidant found in tomatoes, watermelon, guava, papaya, apricots, pink grapefruit, blood oranges, and other foods. Estimates suggest 85 percent of American dietary intake of lycopene comes from tomatoes and tomato products.
Every time they neutralise a free radical, the antioxidant loses an electron and stops being able to function as an antioxidant. This is why you must continually re-supply your body with the vitamins and other chemicals that act as antioxidants.
In light of the role free radicals play in the onset of aging and disease, it is important to ensure our diets include a rich, diverse and constant supply of antioxidants. These protective agents can be found abundantly in vegetables, fruits, nuts and seeds and are particularly high in superfoods, like Carrots!
Research is divided over whether or not antioxidant supplements offer the same health benefits as antioxidants in foods. Antioxidants are compounds in foods that scavenge and neutralise free radicals. Evidence suggests that antioxidant supplements don’t work as well as the naturally occurring antioxidants in foods such as fruits and vegetables.
The Carrot Museum recommends that people eat a wide variety of fresh fruits, vegetables, whole grains, lean meats and dairy products every day. The diet should include five daily serves of fruit and vegetables. One serve is a medium-sized piece of fruit or a half-cup of cooked vegetables.
Of course, in addition to eating plenty of fruits and vegetables, getting regular exercise and abstaining from tobacco use are also critical to a healthy lifestyle
But as always - see your doctor or dietitian and health physician for specific advice.
A bit of history
The term antioxidant (also "antioxygen") originally referred specifically to a chemical that prevented the consumption of molecular oxygen. In the 19th and early 20th century, antioxidants were the subject of extensive research in industrial processes such as the corrosion of metals, explosives, the vulcanization of rubber, and the knocking of fuels in internal combustion engines.
Early nutrition researchers focused on the use of antioxidants for preventing the oxidation of unsaturated fats, the cause of rancidity. Antioxidant activity could be measured simply by placing the fat in a closed glass container with oxygen and observing the rate of oxygen consumption. However, it was the identification of vitamins A, C, and E as antioxidants that revolutionized the field and led to the realization of the importance of antioxidants in biology.
The possible mechanisms of action of antioxidants were first explored thoroughly by Moreau and Dufraisse (1926), who recognized that a substance with anti-oxidative activity is likely to be one that is itself a target for oxidation. Research into how vitamin E prevents the process of lipid peroxidation led to the current understanding of antioxidants as reducing agents that break oxidative chain reactions, often by scavenging reactive oxygen species before they can cause damage to the cells.
NOTE:The information on this website is for informational purposes only and is not intended to be a replacement for medical advice from your personal physician.
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