The main source is plant-based foods, but your body makes some, too. You’re probably familiar with vitamins C and E, beta-carotene, and the minerals selenium and manganese. Plant nutrients and chemicals like flavonoids, phenols, polyphenols, and phytoestrogens are also. “Antioxidants” is one of those buzzwords that gets thrown around a lot, even though most people don't fully understand what it means. We know. Antioxidants are incredibly important, but most people don't really understand what they are. This article explains it all in human terms.
Antioxidants? What are
Because both the ultraviolet light from the sun and the reactive oxygen species generated during photosynthesis would cause irreparable damage, plants produce antioxidants to protect themselves. It is these same antioxidants—vitamins, polyphenols, carotenoids, xanthophylls, and others—in plants that you are able to absorb and use in your own body to protect you from the free radicals generated in your own body.
These antioxidants are necessary to protect you from both the free radicals you normally generate via metabolism, and other sources of free radicals such as environmental stressors. In other words, the more you slow down free radical damage, the slower you age.
This is accomplished from two sides: Antioxidants, it seems, can help you live longer and healthier. There is some evidence to support this. People who eat fruits and vegetables have a lower risk of disease and dementia. There is also strong evidence that a diet high in vegetables, and fruit, may lower the risk of cancer. Vitamins, of course, are essential for health and vitamin deficiencies can lead to diseases. Vitamin A aids vision, immune function, metabolism, reproduction, and skin health.
Vitamin C is essential for the synthesis of collagen and many other structures in your body. Vitamin E also contributes to skin and eye health and has a number of other functions. Carotenes and polyphenols have shown a variety of other benefits: In the eye, the xanthophylls lutein, zeaxanthin, and astaxanthin can all absorb light to help protect the macula of your retina from ultraviolet radiation.
Carotenes and polyphenols have also been shown to prevent redness and support your skin during sun exposure. You can find a little research on antioxidants that promote your defenses against the effects of sun exposure here:. Antioxidants For Supplemental Sun Support. You need antioxidants to prevent free radical damage and lead a healthy life, and obtaining a variety of antioxidants from different foods in a healthy diet seems like a wise choice.
Examples Of Antioxidants There are a variety of different types of antioxidants, including vitamins, enzymes , and other classes of molecules. Enzymes Antioxidant enzymes include glutathione , superoxide dismutase , and coenzyme Q10 ubiquinol. Others Some other types of antioxidants are carotenes including carotenoids such as lycopene and beta-carotene, and xanthophylls including astaxanthin , zeaxanthin, and lutein , polyphenols including tannins, flavonols such as quercitin, catechins such as epigallocatechingallate, cinnamic acids, and many other classes , and alpha-lipoic acid ALA.
Sources Of Antioxidants The antioxidants that you ingest in foods come from many different sources: Vitamin A Liver, sweet potatoes, butter, cheese, carrots, broccoli, and spinach Vitamin C Red peppers, guavas, broccoli, oranges, lemons, pineapples, cauliflower, kale, and cantaloupe Vitamin E Nuts, oils from nuts, olive oil, avocados, and some green leafy vegetables Carotenes Sweet potatoes, carrots, cantaloupe, tomatoes, broccoli, spinach, kale, beets, and many other colorful fruits and vegetables Polyphenols Tea , fruits and vegetables, chocolate, olives, grapes, olive oil, wine, nuts, herbs, and spices Enzymes For enzymatic antioxidants, while they are assembled in your body, they are made from amino acids.
Antioxidants In Plants Plants derive their energy from sunlight via photosynthesis , which generates free radical byproducts call reactive oxygen species. Antioxidants are classified into two broad divisions, depending on whether they are soluble in water hydrophilic or in lipids lipophilic.
In general, water-soluble antioxidants react with oxidants in the cell cytosol and the blood plasma , while lipid-soluble antioxidants protect cell membranes from lipid peroxidation. Some antioxidants are only found in a few organisms and these compounds can be important in pathogens and can be virulence factors. The relative importance and interactions between these different antioxidants is a very complex question, with the various antioxidant compounds and antioxidant enzyme systems having synergistic and interdependent effects on one another.
Some compounds contribute to antioxidant defense by chelating transition metals and preventing them from catalyzing the production of free radicals in the cell. Particularly important is the ability to sequester iron, which is the function of iron-binding proteins such as transferrin and ferritin.
Uric acid is by far the highest concentration antioxidant in human blood. Uric acid UA is an antioxidant oxypurine produced from xanthine by the enzyme xanthine oxidase , and is an intermediate product of purine metabolism. Uric acid has the highest concentration of any blood antioxidant  and provides over half of the total antioxidant capacity of human serum. Ascorbic acid or " vitamin C " is a monosaccharide oxidation-reduction redox catalyst found in both animals and plants.
As one of the enzymes needed to make ascorbic acid has been lost by mutation during primate evolution , humans must obtain it from the diet; it is therefore a vitamin. In other cells, it is maintained in its reduced form by reaction with glutathione, which can be catalysed by protein disulfide isomerase and glutaredoxins.
Glutathione is a cysteine -containing peptide found in most forms of aerobic life. In cells, glutathione is maintained in the reduced form by the enzyme glutathione reductase and in turn reduces other metabolites and enzyme systems, such as ascorbate in the glutathione-ascorbate cycle , glutathione peroxidases and glutaredoxins , as well as reacting directly with oxidants.
Vitamin E is the collective name for a set of eight related tocopherols and tocotrienols , which are fat-soluble vitamins with antioxidant properties. Antioxidants that are reducing agents can also act as pro-oxidants. For example, vitamin C has antioxidant activity when it reduces oxidizing substances such as hydrogen peroxide,  however, it will also reduce metal ions that generate free radicals through the Fenton reaction. The relative importance of the antioxidant and pro-oxidant activities of antioxidants is an area of current research, but vitamin C, which exerts its effects as a vitamin by oxidizing polypeptides, appears to have a mostly antioxidant action in the human body.
That is, paradoxically, agents which are normally considered antioxidants can act as conditional pro-oxidants and actually increase oxidative stress. Besides ascorbate, medically important conditional pro-oxidants include uric acid and sulfhydryl amino acids such as homocysteine. Typically, this involves some transition-series metal such as copper or iron as catalyst. The potential role of the pro-oxidant role of uric acid in e. Another example is the postulated role of homocysteine in atherosclerosis.
As with the chemical antioxidants, cells are protected against oxidative stress by an interacting network of antioxidant enzymes.
This detoxification pathway is the result of multiple enzymes, with superoxide dismutases catalysing the first step and then catalases and various peroxidases removing hydrogen peroxide. As with antioxidant metabolites, the contributions of these enzymes to antioxidant defenses can be hard to separate from one another, but the generation of transgenic mice lacking just one antioxidant enzyme can be informative. Superoxide dismutases SODs are a class of closely related enzymes that catalyze the breakdown of the superoxide anion into oxygen and hydrogen peroxide.
Catalases are enzymes that catalyse the conversion of hydrogen peroxide to water and oxygen, using either an iron or manganese cofactor. Here, its cofactor is oxidised by one molecule of hydrogen peroxide and then regenerated by transferring the bound oxygen to a second molecule of substrate. Peroxiredoxins are peroxidases that catalyze the reduction of hydrogen peroxide, organic hydroperoxides , as well as peroxynitrite.
The thioredoxin system contains the k Da protein thioredoxin and its companion thioredoxin reductase. Plants, such as Arabidopsis thaliana , have a particularly great diversity of isoforms. In its active state, thioredoxin acts as an efficient reducing agent, scavenging reactive oxygen species and maintaining other proteins in their reduced state. The glutathione system includes glutathione, glutathione reductase , glutathione peroxidases , and glutathione S -transferases.
There are at least four different glutathione peroxidase isozymes in animals. Surprisingly, glutathione peroxidase 1 is dispensable, as mice lacking this enzyme have normal lifespans,  but they are hypersensitive to induced oxidative stress. Oxidative stress is thought to contribute to the development of a wide range of diseases including Alzheimer's disease ,   Parkinson's disease ,  the pathologies caused by diabetes ,   rheumatoid arthritis ,  and neurodegeneration in motor neuron diseases.
Here, low density lipoprotein LDL oxidation appears to trigger the process of atherogenesis , which results in atherosclerosis , and finally cardiovascular disease. Oxidative damage in DNA can cause cancer. Several antioxidant enzymes such as superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, glutathione S-transferase etc. It has been proposed that polymorphisms in these enzymes are associated with DNA damage and subsequently the individual's risk of cancer susceptibility.
A low calorie diet extends median and maximum lifespan in many animals. This effect may involve a reduction in oxidative stress. Antioxidants are used as food additives to help guard against food deterioration. Exposure to oxygen and sunlight are the two main factors in the oxidation of food, so food is preserved by keeping in the dark and sealing it in containers or even coating it in wax, as with cucumbers.
However, as oxygen is also important for plant respiration , storing plant materials in anaerobic conditions produces unpleasant flavors and unappealing colors. Antioxidants are an especially important class of preservatives as, unlike bacterial or fungal spoilage, oxidation reactions still occur relatively rapidly in frozen or refrigerated food. The most common molecules attacked by oxidation are unsaturated fats; oxidation causes them to turn rancid.
Thus, these foods are rarely preserved by drying; instead, they are preserved by smoking , salting or fermenting. Even less fatty foods such as fruits are sprayed with sulfurous antioxidants prior to air drying. Oxidation is often catalyzed by metals, which is why fats such as butter should never be wrapped in aluminium foil or kept in metal containers.
Some fatty foods such as olive oil are partially protected from oxidation by their natural content of antioxidants, but remain sensitive to photooxidation. Antioxidants are frequently added to industrial products.
A common use is as stabilizers in fuels and lubricants to prevent oxidation, and in gasolines to prevent the polymerization that leads to the formation of engine-fouling residues. Antioxidant polymer stabilizers are widely used to prevent the degradation of polymers such as rubbers, plastics and adhesives that causes a loss of strength and flexibility in these materials. They can be protected by antiozonants.
Solid polymer products start to crack on exposed surfaces as the material degrades and the chains break. The mode of cracking varies between oxygen and ozone attack, the former causing a "crazy paving" effect, while ozone attack produces deeper cracks aligned at right angles to the tensile strain in the product. Oxidation and UV degradation are also frequently linked, mainly because UV radiation creates free radicals by bond breakage. The free radicals then react with oxygen to produce peroxy radicals which cause yet further damage, often in a chain reaction.
Other polymers susceptible to oxidation include polypropylene and polyethylene. The former is more sensitive owing to the presence of secondary carbon atoms present in every repeat unit. Attack occurs at this point because the free radical formed is more stable than one formed on a primary carbon atom. Oxidation of polyethylene tends to occur at weak links in the chain, such as branch points in low-density polyethylene.
Antioxidant vitamins are found in vegetables, fruits, eggs, legumes and nuts. Vitamins A, C, and E can be destroyed by long-term storage or prolonged cooking. Other antioxidants are not obtained from the diet, but instead are made in the body. For example, ubiquinol coenzyme Q is poorly absorbed from the gut and is made through the mevalonate pathway. As any glutathione in the gut is broken down to free cysteine, glycine and glutamic acid before being absorbed, even large oral intake has little effect on the concentration of glutathione in the body.
Measurement of antioxidant content in food is not a straightforward process, as antioxidants collectively are a diverse group of compounds with different reactivities to various reactive oxygen species.
In food science , the oxygen radical absorbance capacity ORAC was once an industry standard for estimating antioxidant strength of whole foods, juices and food additives, mainly from the presence of polyphenols. Alternative in vitro measurements of antioxidant content in foods — also based on the presence of polyphenols — include the Folin-Ciocalteu reagent , and the Trolox equivalent antioxidant capacity assay.
As part of their adaptation from marine life, terrestrial plants began producing non-marine antioxidants such as ascorbic acid vitamin C , polyphenols and tocopherols. In the late 19th and early 20th centuries, extensive study concentrated on the use of antioxidants in important industrial processes, such as the prevention of metal corrosion , the vulcanization of rubber, and the polymerization of fuels in the fouling of internal combustion engines. Early research on the role of antioxidants in biology focused on their use in preventing the oxidation of unsaturated fats , which is the cause of rancidity.
However, it was the identification of vitamins C and E as antioxidants that revolutionized the field and led to the realization of the importance of antioxidants in the biochemistry of living organisms. From Wikipedia, the free encyclopedia. A compound that inhibits the oxidation of other molecules. Pathology , Free-radical theory , and Oxidative stress. List of antioxidants in food and Polyphenol antioxidant.
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H2O2, a necessary evil for cell signaling". Molecular and Cellular Biochemistry.
Antioxidants help prevent free radicals from damaging your cells. They are found in a lot of fruits and vegetables, as well as supplements. Antioxidants are man-made or natural substances that may prevent or delay some types of cell damage. Antioxidants are found in many foods, including fruits . Oxygen free radicals set off damaging and lethal chain reactions within cells. Antioxidants reduce oxidative damage and may therefore slow ageing.