Information AboutAntioxidant |
| CATEGORIES ABOUT ANTIOXIDANT | |
| antioxidants | |
| physiology | |
| SHOPPER'S DELIGHT | |
|
An antioxidant is a substance that slows or halts s and/or Enzyme s to prevent chemical damage to the cells' components by oxidation. However, plants are the most important source of organic antioxidant chemicals, and a diet containing antioxidants from plants are required for the health of most Mammals . The importance and complexity of antioxidants in biology is reflected in a medical literature of more than 142,000 scholarly articles {Link without Title} . Antioxidants are widely used as ingredients in Dietary Supplements that are used for health purposes such as preventing cancer and heart disease. However, while many studies have suggested benefits for antioxidant supplements, several large Clinical Trial s have failed to clearly demonstrate a benefit for the formulations tested, and excess supplementation may be harmful. 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, explosions, the Vulcanization of rubber, and the knocking of fuels in internal combustion engines (Mattill 1947). Early nutrition researchers focused on the use of antioxidants for preventing the oxidation of unsaturated fats (which made them rancid). 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 for the action of antioxidants was 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 Agent s that break oxidative chain reactions, often by scavenging Reactive Oxygen Species before they can cause damage to the cells (Wolf 2005). ANTIOXIDANTS IN BIOLOGY In biological systems, the normal processes of oxidation (plus contributions from Ionizing Radiation and pro-oxidant chemicals) produce highly reactive Free Radical s. These can readily react with and damage other molecules, including DNA in cell nuclei or mitochondria. In some cases, the body uses free radicals to destroy foreign or unwanted objects, such as in an infection or cancer. However, in the wrong place, the body's own Cells may become damaged. Should the damage occur to DNA, the result could increase the possibility of cancer. Antioxidants decrease the damage done to cells by Reducing oxidants before they can damage the cell. Antioxidants may be further classified by the products they form on oxidation (these can be antioxidants themselves, inert, or pro-oxidant), by what happens to the oxidation products (the antioxidant may be regenerated by different antioxidants or, in the case of "sacrificial" antioxidants, its oxidised form may be broken down by the organism) and how effective the antioxidant is against specific free radicals. Free radical damage in the Mitochondria of living cells is a byproduct of Aerobic Metabolism . Superoxide radicals are generated, which can damage mitochodria and mitochondrial membranes. Unlike DNA in the Cell Nucleus , mitochondrial DNA has only a few DNA-repair Enzyme s and the DNA is not protected by Histone s. Cells have evolved antioxidant chemicals and enzymes that work together to tightly regulate the Redox State of the cell and to protect from damage by Reactive Oxygen Species . Important examples include:
APPLICATIONS IN NUTRITION AND IN MEDICINE How antioxidants preserve health Free Radicals are atoms or molecules with unpaired electrons, making them highly reactive and oxidative. Some of the common free radicals inside the human body are the hydroxyl, peroxide, and superoxide radicals, and metal ions. Free radicals serve important functions inside the body, but they can also damage cells and biochemicals. Antioxidants are chemicals that bind with and destroy free radicals, reducing oxidative damage to cells and biochemicals. Researchers have found high correlation between oxidative damage to cells and biochemicals, and the occurrence of disease. For example, LDL oxidation is associated with cardiovascular disease. The process leading to atherogenesis, artherosclerosis, and cardiovascular disease is complex, involving multiple chemical pathways and networks, but the precursor is LDL oxidation by free radicals, resulting in inflammation and formation of plaques. Research suggests that consumption of antioxidant-rich foods reduces damage to cells and biochemicals from free radicals. This can slow down, prevent, and even reverse certain diseases that result from cellular damage, and perhaps even slow down the natural aging process (see Free-radical Theory of aging). Some of the reactions in the body that produce free radicals involve metal ions. Futhermore, metal ions are themselves free radicals that can cause oxidation directly. Some antioxidants, such as the Tannins in walnuts, chelate (wrap around) metal ions. This not only reduces the formation of ion-dependent free radicals, but also prevents the metal ions from oxidizing cells and biochemicals directly. By destroying free radicals and reducing cellular damage, antioxidants, as a group, can:
Any specific antioxidant may perform only a small fraction of these functions. Dietary antioxidants are not the primary antioxidant inside the body, and there are still many questions as to how polyphenols and other dietary antioxidants protect cells and biochemicals from oxidation. Some antioxidants preserve, or even recycle, other antioxidants such as vitamin E. Some antioxidants have far-reaching effects, such as moderating insulin, that are not clearly understood. How some antioxidants can harm health Some of the plant based reducing acids, most notably Oxalic and Phytic , bind to needed dietary minerals, rendering them unabsorbable in the gastrointestinal tract. Some of the Tannin s also have this negative characteristic. Calcium and iron deficiencies are not uncommon in mideastern diets where there is high consumption of Phytic Acid present in beans and unleavened Whole Grain bread. Such antinutrients can sometimes result in deceptively high Oxygen Radical Absorbance Capacity (ORAC) ratings given to various "healthy" beverages and foods, particularly:
Other extremely powerful Nonpolar antioxidants such as Eugenol also happen to have toxicity limits that can easily be exceeded with the misuse of Essential Oils . High levels of antioxidants can be powerful agents against tumours, but in some scenarios can interfere with the effects of other cancer treatments. Recent laboratory studies suggest that at levels much higher than occur through normal diets, antioxidant vitamins such as A, E and C can have pro-oxidant effects, increasing the formation of free radicals. Natural antioxidants are always ingested together with a wide variety of Flavonoids and other Phytochemicals are also likely to play a part. Many supplement manufacturers supply products containing antioxidants in combination with these other natural chemicals. Another significant factor is that the mechanisms by which different antioxidants regenerate each other require balanced levels to work optimally. Newer liquid nutritional supplements using plant ionic compounds are believed to be more readily absorbed in the human body. Calorie restriction and reduced oxidative stress Virtually all studies of mammals have concluded that a Restricted Calorie Diet (CR) extends median and maximum lifespan (CR is almost the only protocol to have achieved this). This benefit appears to be at least partly due to substantially reduced oxidative stress Very large increases in lifespan (up to around 100%) have only been observed in short lived species and the effect in humans is expected to be far less dramatic. The best evidence from animal studies is likely to come from ongoing studies in primates where median life spans have already been shown to be increased and biomarkers of health significantly improved. Due to the long life span of primates, confirmation of maximum lifespan increase will not be available until around 2014 [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=10630591&query_hl=8&itool=pubmed_DocSum . The striking results from animal experiments provide strong evidence that an excess of food reduces life expectancy, although the relationship is not a simple one. Other research suggests that being a little overweight is actually a healthier option in humans (New Scientist 26 November 2005), and a recent major study concluded that mortality rates were positively correlated with waist size, but for a fixed waist size mortality rates were negatively correlated with body mass index (particularly for underweight subjects) [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=15930225&query_hl=25&itool=pubmed_docsum]. As food produces free radicals (oxidants) when metabolized, antioxidant-rich diets are thought to stave off the effects of aging significantly better than diets lacking in antioxidants. Clinical trials of antioxidant supplements Although some levels of antioxidant vitamins and minerals in the diet are required for good health, there is considerable doubt as to whether antioxidant supplementation is beneficial, and if so, which and what amount of antioxidant(s) are optimal. One study of lung cancer patients found that those given beta-carotene supplements had worse prognoses. Two 1994 studies found an increased rate of lung cancer in smokers supplementing with beta carotene. This is believed to be due to antioxidant interference with the body's normal use of localised free radicals e.g. Nitric Oxide for cell signalling. Due to the complex nature of the interactions of antioxidants with the body, it is difficult to interpret the results of many experiments. In vitro testing (outside the body) has shown many natural antioxidants, in specific concentration, can halt the growth of or even kill cancerous cells. In the early 1990s, it was hypothesized that oxidation of LDL Cholesterol contributes to heart disease, and several observational studies found that people taking Vitamin E supplements had a lower risk of developing heart disease (Rimm 1993). Taken together, this led researchers to conduct at least seven large clinical trials testing the effects of antioxidant supplement with Vitamin E, in doses ranging from 50 to 600 mg per day. However, none of these trials found a statistically significant effect of Vitamin E on overall number of deaths or on deaths due to heart disease (Vivekananthan 2003). While several trials have investigated supplements with high doses of antioxidants, the "Supplementation en Vitamines et Mineraux Antioxydants" (SU.VI.MAX) study tested the effect of supplementation with doses comparable to those in a healthy diet (Hercberg 2003). Over 12,500 French men and women took either low-dose antioxidants (120 mg of ascorbic acid, 30 mg of vitamin E, 6 mg of beta carotene, 100 g of selenium, and 20 mg of zinc) or Placebo pills for an average of 7.5 years. The investigators found there was no statistically significant effect of the antioxidants on overall survival, cancer, or heart disease. However, a subgroup analysis showed a 31% reduction in the risk of cancer in men, but not women. The authors interpreted these results as suggesting that "an adequate and well-balanced supplementation of antioxidant nutrients, at doses that might be reached with a healthy diet that includes a high consumption of fruits and vegetables, had protective effects against cancer in men." The significant effect of supplementary selenium in reducing incidence of prostate cancer was strongly supported by the Nutrition for the Prevention of Cancer (NPC) trial (designed primarily to determine the effect of selenium supplementation on skin cancers) and found significant effects for subjects whose plasma selenium levels were in the middle and lower thirds, but not for those in the top third. The SELECT project further investigating the effects of selenium supplementation (in combination with vitamin E) on prostate cancer incidence, but final results will not be available until 2013 [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=15753149&query_hl=5&itool=pubmed_docsum . ANTIOXIDANTS IN FOOD INDUSTRY - FOOD PRESERVATIVES Antioxidants used as Food Additive s to help Guard Against Food Deterioration include:
FOOD SUPPLEMENTS Many Nutraceutical and health food companies have, in light of scientific studies, produced products that supplement the diet with antioxidants. Many companies have products that are explicitly composed of derivatives that contain antioxidants, like Resveratrol in grape seeds. Other companies produce supplements that contain a combination of antioxidants, like elagic acid with tummeric, or the ubiquitous "ACES" formulas that contain beta carotene (provitamin A), vitamin '''C''', vitamin '''E''' and '''S'''elenium often with additional antioxidants and nutrients. Specialty herbs such as Green Tea and Jiaogulan have benefitted tremendously from recent articles on antioxidants in green tea delaying onset of age-related Macular Degeneration . Antioxidants especially recognized for their liver protective properties as well as other uses in conventional, Naturopathic and Orthomolecular Medicine include:
Nutritional antioxidants There are hundreds of different types of antioxidants. The following substances have shown positive nutritional antioxidant effects: Vitamins
Vitamin cofactors and minerals
Hormones
Carotenoid terpenoids
Non-carotenoid terpenoids ''' and Cinnamon . Saponins and limonoids ''Editor's note: Not certain if these are antioxidants; work in progress...'' Flavonoid polyphenolics (also known as bioflavonoids) Bioflavonoids are present in many dark berries such as pomegranate, Seabuckthorn , Noni , blueberries, and blackberries, as well as in certain types of Tea and Coffee , especially Green Tea . Coffee is often depleted of antioxidants due to the high-temperature roasting process. The US FDA may have recently suggested that the average person should consume up to 7000 ORAC units daily, in order to reduce the risk of cancer. As this is nearly 12 servings of high-ORAC-value fruit, the use of nutritional supplements containing bioflavonoids is likely necessary to reach this target. Flavonols:
Flavones: Flavanones:
Flavan-3-ols (anthocyanidins):
Isoflavone Phytoestrogens - found primarily in soy, peanuts, and other members of the Fabaceae family. Besides having antioxidant characteristics, isoflavones also protect and maintain the skeletal system.
Anthocyanins protect plants from UV damage:
Phenolic acids and their esters
Other nonflavonoid phenolics Other (someone please classify):
Other organic antioxidants
BEVERAGES AND FOODS HIGHEST IN ANTIOXIDANTS #1 Undutched Cocoa powder #2 Dark, semisweet Chocolate ; particularly that which is 85% cocoa solids #3 White Tea #4 Green Rooibos #5 Green Tea #6 Red Rooibos #7 Oolong tea #8 Black Tea Certain fruits and berries, especially: #9 Blueberry (especially '''wild''' blueberry; AKA ''' Bilberry ''') contain more antioxidants than any other fruit or vegetable, when compared on the basis of equal calories. They are high in anthocyanins, Chlorogenic Acid , ellagic acid, catechins, and resveratrol.
Leafy, dark green cruciferous vegetables:
Certain other vegetables, especially:
Generally, the deeper and richer the color of fruits and vegetables, the higher the quantity of antioxidants. Many fruits and vegetables are also high in fiber, minerals, and vitamins. Note, however, that the most commonly eaten fruits and vegetables (apples, bananas, iceberg lettuce, and potatoes) are not on the list. Fruit juice can contain some antioxidants, but not nearly as much as the fruit from which they are made (antioxidants are concentrated in the skins and pulps), and fruit juice tends to consist primarily of corn syrup and water. To consume the greatest quantity of antioxidants, try to eat a variety of foods, and buy fruits and vegetables locally when they are in season. Note that the color rule of thumb does not apply to varieties of tea. The darker the variety of tea, the lower is its antioxidant concentration. Nuts, especially:
Besides being high in polyphenols, nuts are also high in beneficial, unsaturated fatty acids. There is a correlation between nut consumption and a reduced incidence of ischemic heart disease. This is most likely due partly to the favorable lipid content and partly to the high polyphenol content. Walnuts have the highest phenolic content, which is why they taste bitterer than pecans and hazelnuts. To help preserve the antioxidants in nuts, keep them in a freezer. They have almost no water, so the freezer won’t harm them. Certain herbs and spices. Even though people typically use spices in small amounts, some spices have extremely high antioxidant content per unit mass, especially:
Tea, esp. white tea - high in polyphenols and tannins. Seeds and grains, especially:
Other plants:
List of the 20 foods with the highest concentration of antioxidants (“total antioxidant capacity”), according to the USDA:
Foods that score well in Oxygen Radical Absorbance Capacity:
ANTIOXIDANTS IN FUELS Some antioxidants are added to liquid industrial chemicals, most often Fuel s and Lubricant s to prevent oxidation, and in gasolines to prevent polymerization leading to Gumming . Some examples are:
Antioxidants are frequently used together with Metal Deactivator s and Corrosion Inhibitor s. REFERENCES
EXTERNAL LINKS
|