KFD.PL: Antyoksydanty - Forum KFD.pl

Poza tym ani wit C ani wit E nie są witaminami chemicznej rodziny witaminy A. Beta karoten jak i większość karotenoidów są przekształcane w witaminę A.

Troszkę rozjaśnię
Antyoksydanty występują powrzechnie w rożnych formach generalnie bardzo silnie działającymi są flawonoidy(antocyjany, antocyjanozydy, antocyjanonidyny, flawonolignany, izoflawony ,proantocyjanidy, flawonole, flawony, dwuflawony, flawanony, flawononole), glutation, karotenoidy ( np. beta karoten, alfa karoten, kryptoksantyna, zeaksantyna, likopen, luteina), selen, cynk, kwas liponowy, niektóre aminokwasy,koenzym Q 10, hormony ( DHEA i melatonina), enzymy ( dysmutaza nadtlenkowa, katalaza, peroksydaza glutationowa, reduktaza glutationowa, transferaza glutationowa) itp jak widać z powyższego kawal zakresu chemii organicznej z elementami biochemii i niestety wszystko to znajdziemy w żywności więć możemy z nią dostarczać mniej lub więcej antyoskydatów. Warto patrzeć co jemy

Wolne rodniki to
- rodnik ponadtlenkowy
- rodnik hydroksylowy
- tlen singletowy
- nadazotanowy
Występują naturalnie w naszym organiźmie i poza tym że oczywiściw wyrządzają duże szkody to jednak są niezbędne. Ich redukcję warto prowadzić zawsze mimo , że organizym ma mechanizmy walki z nimi na poziomie komórkkowym to jednak w realich obecnego świata i potęgowaniu się czynników stresotwórczych nie zawsze daje sobie z tym radę więc warto patrzeć na to co zjadamy bo w ten sposób dostarczamy dobroczynnych antyoxydantów które tak na marginesie jeżeli w nadmiarze to tez mogą przejść na ciemna stronę mocy stając się prooksydantami czyli nie wymiatają rodników lecz je tworzą.

Ogólnie temat szeroki tak bardzo jak ciekawy

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Praktycznie wszyscy eksperci są zgodni, iż codzienne zażywanie multiwitaminowych preparatów nikomu nie zaszkodzi. Opinie są jednak podzielone, gdy chodzi o fakt, czy ludzie powinni przyjmować duże dawki witamin w celu zapobiegania przewlekłej choroby lub opóźnienia starzenia. Niektórzy uczeni twierdzą, że dowody są wystarczające, aby podjąć takie działanie. Przeprowadzono ogromną ilość badań, a ponad 30.000 Opublikowano. Te doświadczenia są nadal celem badań i prowadzone są pod ścisłą obserwacją.


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Individuals with low levels of physical activity are at risk for high levels of oxidative stress , as are individuals engaged in highly intensive exercise programs; however individuals engaged in moderately intensive, regular exercise experience lower levels of oxidative stress. High levels of oxidative stress have been linked by some with the increased incidence of a variety of diseases [ 5 ] , It has been claimed that this relationship, characterized by positive effects at an intermediate dose of the stressor (exercise), is characteristic of hormesis [ 6 ] . However, it is important to point out that there is evidence that the oxidative stress associated with intensive exercise may have long term health benefits. This would imply that oxidative stress, itself, provides an example of hormesis (see section on Mitochondrial hormesis ), but physical exercise does not. [ 7 ]

Mitochondria are sometimes described as "cellular power plants" because they generate most of the cell's supply of adenosine triphosphate (ATP), a source of chemical energy. Reactive oxygen species (ROS) have been regarded as unwanted by-products of oxidative phosphorylation in mitochondria by the proponents of the free-radical theory of aging promoted by Denham Harman . The free-radical theory suggests that the use of compounds which inactivate ROS, such as so-called antioxidants , would lead to a reduction of oxidative stress and thereby produce an increase in lifespan. However in clinical trials the expected health-promoting effects of antioxidants were not found and results suggested that antioxidants may promote cancer in humans. Other studies have now shown that antioxidant supplements may be disease-promoting and increase mortality in humans. [ 22 ]

ROS may perform an essential and potentially lifespan-promoting role as redox signaling molecules which transduce signals from the mitochondrial compartment to other compartments of the cell. Increased formation of reactive oxygen species (ROS) within the mitochondria may cause an adaptive reaction which produces increased stress resistance and a long-term reduction of oxidative stress. This kind of reverse effect of the response to ROS stress has been named mitochondrial hormesis or mitohormesis and is hypothesized to be responsible for the respective lifespan-extending and health-promoting capabilities of glucose restriction and physical exercise. [ 22 ]

Hormesis may also be induced by endogenously produced, potentially toxic agents. For example, mitochondria consume oxygen which generates free radicals ( reactive oxygen species ) as an inevitable by-product. It was previously proposed on a hypothetical basis that such free radicals may induce an endogenous response culminating in increased defense capacity against exogenous radicals (and possibly other toxic compounds). [ 23 ] Recent experimental evidence strongly suggests that this is indeed the case, and that such induction of endogenous free radical production extends life span of a model organism. Most importantly, this extension of life span is prevented by antioxidants , providing direct evidence that toxic radicals may mitohormetically exert life extending and health promoting effects. [ 24 ] Since mitochondrial activity was found to be increased in the before-mentioned studies, this effect cannot be explained by an excess of free radicals that might mark mitochondria for destruction by lysosomes , with the free radicals acting as a signal within the cell to indicate which mitochondria are ready for destruction, as proposed by Nick Lane . [ 25 ]

Another study on yeasts explains the underlying mechanism of the process that prevents cellular damage by reactive oxygen species . [ 26 ] Whether this concept applies to humans remains to be shown, although recent epidemiological findings support the process of mitohormesis , and even suggest that some antioxidant supplements may increase disease prevalence in humans. [ 2

Antioxidants Fall From Grace

To anyone who feels guilty for not gorging on antioxidants—actually, make that “antioxidants!,” which seems to be how grocery manufacturers think of them—redemption is nigh. For years the media, food labels, dietitians, and even scientists who should know better have bombarded us with advice to load up on antioxidants: compounds found (mostly) in fruits and vegetables that mop up free radicals, which are highly reactive clusters of atoms that have been fingered as the evildoers responsible for aging and for illnesses from cancer to heart disease.

Not so fast. First, studies piled up showing that taking antioxidants—even such common and seemingly innocuous ones as beta carotene and vitamins C and E—as supplements was not beneficial to health and might even be dangerous, though the reason for the danger wasn’t clear. (One always pays attention when a study concludes with a phrase like “seems to increase overall mortality.”) Now the research is challenging an even more fundamental tenet of the antioxidant craze. Many of the free radicals that are neutralized by antioxidants perform valuable functions in the body. The most important: fighting toxins (white blood cells churn out free radicals by the battalion to fight bacterial infection) and fighting cancer. Maybe it’s not such a fabulous idea to flood the body with something that neutralizes these warriors of the immune system. Or as British chemist and science writer David Bradley noted in his blog, Reactive Reports, “It’s always struck me as odd that you would want to ingest extra antioxidants anyway, given that oxidising agents are at the front-line of immune defence against pathogens and cancer cells ... Suffice to say that taking antioxidant supplements ... may not necessarily be good for your health if you already have health problems,” especially cancer or an infection.
The first hints that the bandwagon was crashing came from the hundreds of studies that have tried to assess the health effects of antioxidant supplements. The results have not been pretty. In 2008 the Cochrane Collaboration, an international consortium of scientists who assess medical research, scrutinized 67 studies with nearly 400,000 participants. The goal: to determine whether antioxidant supplements reduce mortality in either healthy people or in people with cardiovascular, neurological, rheumatoid, renal, endocrine, or other diseases. Conclusion: “We found no evidence to support antioxidant supplements for primary or secondary prevention, [and] Vitamin A, beta-carotene, and vitamin E may increase mortality.” In analyses of antioxidant supplements and Lou Gehrig’s disease, Alzheimer’s or mild cognitive impairment, and lung cancer, the Cochrane scientists’ verdict was the same: no, no, no, and no. And each analysis had an alarming refrain about increasing overall mortality.

It’s not clear why antioxidants in supplement form might be so dangerous. One idea holds that at high doses they become pro-oxidants, stimulating the harmful DNA- and cell-damaging reactions they’re supposed to prevent. But a more likely explanation is that we are seeing the human version of what scientists are finding in studies of lab animals: antioxidants interfere with immune-system cells that fight infection and cancer.
For those who got to this party late, free radicals are generated by normal metabolism, though dietary fat and iron-rich foods such as red meat generate more of them. Free radicals can damage proteins, fats, carbohydrates, and DNA—the biological stuff we’re made of. They also harm the cells that line blood vessels, enabling tumor cells to enter the bloodstream and metastasize. All this destruction, explains Jeffrey Blumberg, director of the Antioxidants Research Lab at Tufts University, “is believed to initiate, promote, or stimulate the progression of many chronic diseases, including cardiovascular disease and cancer,” as well as normal aging. “The hypothesis that emerged is that if you prevent the damage, you prevent the disease.”

That was music to the ears of food manufacturers, especially as research suggested that some antioxidants are better than others at quenching different free radicals. Beta carotene, for instance, slays superoxide dismutase, but vitamin E is relatively impotent against it. On the other hand, vitamin E makes LDL (“bad” cholesterol) more resistant to oxidation, which should be good for health: oxidized LDL is more likely to form plaque deposits that clog arterial walls. The different functions of different antioxidants opened the door to marketers pushing supplements for each one, as well as otherwise-unhealthy foods fortified with a cornucopia of antioxidants (Chocolatey Peanut Butter FiberPlus Antioxidants, anyone?).
In addition to the alarming findings from studies of people who take antioxidant supplements, new research is casting doubt on the benefits even more directly:

• A paper to appear in an upcoming issue of the Proceedings of the National Academy of Sciences finds that antioxidants might impair fertility. When scientists led by developmental biologist Nava Dekel of Israel’s Weizmann Institute of Science applied antioxidants to the ovaries of female mice, ovulation levels plummeted: follicles released very few eggs. That suggested that ovulation might require the free radicals that antioxidants neutralize. Further experiments confirmed it: a type of free radical called reactive oxygen species is produced in response to luteinizing hormone, the physiological trigger for ovulation. That suggests that luteinizing hormone triggers ovulation through an intermediary—namely, reactive oxygen species. If reactive oxygen species are being mopped up by antioxidants, there’s no ovulation.

• A 2010 study in lab rats found that two popular antioxidants, quercetin (found in black and green tea, red onion, and other plant foods) and ferulic acid (in apples, artichokes, wheat, and other plants), aggravated and possibly triggered kidney cancer. As the scientists put it in the Journal of Agricultural and Food Chemistry, “It is time to reevaluate the tumorigenic detrimental effect of” antioxidants.

• Finally, a new study in lab mice finds that a natural protein that boosts antioxidant levels in the blood may actually promote atherosclerosis, or clogging of the arteries. The study, in the January issue of Arteriosclerosis, Thrombosis, and Vascular Biology, offers clues about why taking antioxidants has not been shown to improve heart health. The protein Nrf2 indeed boosts antioxidants, but in the study it also raised blood-cholesterol levels, as well as cholesterol content in the liver—both of which are excellent ways to get atherosclerosis.

In 2009, 108 new food products with antioxidants touted on the label reached store shelves in the United States, according to the market-research firm Mintel. That compares with 16 in 2005 and 82 in 2007. “Buyer beware” doesn’t begin to cover it.