Antioxidants are compounds that inhibit oxidation. Oxidation is a chemical reaction that can produce free radicals, thereby leading to chain reactions that may damage the cells of organisms. Antioxidants such as thiols or ascorbic acid terminate these chain reactions. To balance the oxidative stress and animals maintain complex systems of overlapping antioxidants, such as glutathione and enzymes, produced internally, or the dietary antioxidants vitamin C and vitamin E; the term "antioxidant" is used for two different groups of substances: industrial chemicals that are added to products to prevent oxidation, occurring compounds that are present in foods and tissue. The former, industrial antioxidants, have diverse uses: acting as preservatives in food and cosmetics, being oxidation-inhibitors in fuels. Antioxidant dietary supplements have not been shown to improve health in humans, or to be effective at preventing disease. Supplements of beta-carotene, vitamin A, vitamin E have no positive effect on mortality rate or cancer risk.

Additionally, supplementation with selenium or vitamin E does not reduce the risk of cardiovascular disease. Although certain levels of antioxidant vitamins in the diet are required for good health, there is still considerable debate on whether antioxidant-rich foods or supplements have anti-disease activity. Moreover, if they are beneficial, it is unknown which antioxidants are health-promoting in the diet and in what amounts beyond typical dietary intake; some authors dispute the hypothesis that antioxidant vitamins could prevent chronic diseases, others declare that the hypothesis is unproven and misguided. Polyphenols, which have antioxidant properties in vitro, have unknown antioxidant activity in vivo due to extensive metabolism following digestion and little clinical evidence of efficacy. Common pharmaceuticals with antioxidant properties may interfere with the efficacy of certain anticancer medication and radiation therapy. Strong reducing acids can have antinutrient effects by binding to dietary minerals such as iron and zinc in the gastrointestinal tract and preventing them from being absorbed.

Examples are oxalic acid and phytic acid, which are high in plant-based diets. Calcium and iron deficiencies are not uncommon in diets in developing countries where less meat is eaten and there is high consumption of phytic acid from beans and unleavened whole grain bread. High doses of some antioxidants may have harmful long-term effects; the beta-Carotene and Retinol Efficacy Trial study of lung cancer patients found that smokers given supplements containing beta-carotene and vitamin A had increased rates of lung cancer. Subsequent studies confirmed these adverse effects; these harmful effects may be seen in non-smokers, as one meta-analysis including data from 230,000 patients showed that β-carotene, vitamin A or vitamin E supplementation is associated with increased mortality, but saw no significant effect from vitamin C. No health risk was seen when all the randomized controlled studies were examined together, but an increase in mortality was detected when only high-quality and low-bias risk trials were examined separately.

As the majority of these low-bias trials dealt with either elderly people, or people with disease, these results may not apply to the general population. This meta-analysis was repeated and extended by the same authors, confirming the previous results; these two publications are consistent with some previous meta-analyses that suggested that vitamin E supplementation increased mortality, that antioxidant supplements increased the risk of colon cancer. Beta-carotene may increase lung cancer. Overall, the large number of clinical trials carried out on antioxidant supplements suggest that either these products have no effect on health, or that they cause a small increase in mortality in elderly or vulnerable populations. A paradox in metabolism is that, while the vast majority of complex life on Earth requires oxygen for its existence, oxygen is a reactive molecule that damages living organisms by producing reactive oxygen species. Organisms contain a complex network of antioxidant metabolites and enzymes that work together to prevent oxidative damage to cellular components such as DNA, proteins and lipids.

In general, antioxidant systems either prevent these reactive species from being formed, or remove them before they can damage vital components of the cell. However, reactive oxygen species have useful cellular functions, such as redox signaling. Thus, the function of antioxidant systems is not to remove oxidants but instead to keep them at an optimum level; the reactive oxygen species produced in cells include hydrogen peroxide, hypochlorous acid, free radicals such as the hydroxyl radical and the superoxide anion. The hydroxyl radical is unstable and will react and non-specifically with most biological molecules; this species is produced from hydrogen peroxide in metal-catalyzed redox reactions such as the Fenton reaction. These oxidants can damage cells by starting chemical chain reactions such as lipid peroxidation, or by oxidizing DNA or proteins. Damage to DNA can cause mutations and cancer, if not reversed by DNA repair mechanisms, while damage to proteins causes enzyme inhibition and protein degradation.

The use of oxygen as part of the process for generating metabolic energy produces reactive oxygen species. In this process, the superoxide anion is produced as a by-product of several steps in the electron transport chain. Important is the reduction of coenzyme Q in complex III, since a reactive free radical is

Section Paloise Béarn Pyrénées called Pau, is a French rugby union club from Pau in Pyrénées-Atlantiques competing in Top 14, the highest level of the French league system. They most earned promotion by winning the championship of the second-level Rugby Pro D2 in 2015, nine years after having been relegated from the top flight, they were founded in 1902 as Section Paloise de la Ligue Girondine before adopting their current name in 1905, which refers to the ancient region of Béarn and to the Pyrenees mountains. Section Paloise first joined the French first division in 1911, were crowned champions for the first time in 1928. "La Section" have won the French Championship on three occasions, the last being in 1964. They have, reached the semi-finals of the Heineken Cup and Top 14 as as 1998 and 2000, respectively. Section Paloise added to their trophy case in 2000, winning the European Challenge Cup. At the end of the 2004–05 season, "La Section" survived a play-off game with Aurillac to remain in the Top 16.

However, they were relegated the following season, would remain in Pro D2 until earning promotion for the 2015–16 season. The club colors are green and white and their home ground is the Stade du Hameau, they are sponsored by French petroleum company Total. Recent France internationals Imanol Harinordoquy, Damien Traille, Lionel Beauxis began their professional club careers with Section Paloise. French premiership Champions: 1928, 1946, 1964 Challenge Yves du Manoir Champions: 1939, 1952, 1997 European Challenge Cup Champions: 2000 Rugby Pro D2 Champions: 2015 The Pau squad for the 2019–20 season is:Note: Flags indicate national union as has been defined under WR eligibility rules. Players may hold more than one non-WR nationality. List of rugby union clubs in France Rugby union in France Section Paloise Official website

This list shows an overview of postal code notation schemes for all countries that have postal or ZIP code systems. LegendA = letter N = number? = letter or number CC = ISO 3166-1 alpha-2 country code The use of the country codes in conjunction with postal codes started as a recommendation from CEPT in the 1960s. In the original CEPT-recommendation the distinguishing signs of motor vehicles in international traffic were placed before the postal code, separated from it by a "-". Codes were only used on international mail and were hardly used internally in each country. Since the late 1980s, however, a number of postal administrations have changed the recommended codes to the two-letter country codes of ISO 3166; this would allow a universal, standardized code set to be used, bring it in line with country codes used elsewhere in the UPU. Attempts were made to make this part of the official address guidelines of the UPU. Introduced postal code systems where the UPU has been involved have included the ISO 3166 country code as an integral part of the postal code.

At present there are no universal guidelines as to which code set to use, recommendations vary from country to country. In some cases, the applied country code will differ according to recommendations of the sender's postal administration. UPU recommends. In the list above, the following principles have been applied: Integral country codes have been included in the code format, in bold type and without brackets; these are used on internal mail in the respective countries. The ISO 3166 codes is used alone for countries. Where there is no explicit recommendation for ISO 3166 codes and the codes differ, both "car codes" and ISO 3166 codes are listed, with the "car code" listed first. Universal Postal Union "Postal addressing systems in member countries". Berne: Universal Postal Union. Retrieved 11 January 2018. Updated