Adverse effects Antioxidant

structure of metal chelator phytic acid.

relatively strong reducing acids can have antinutrient effects binding dietary minerals such iron , zinc in gastrointestinal tract , preventing them being absorbed. notable examples oxalic acid, tannins , phytic acid, high in plant-based diets. calcium , iron deficiencies not uncommon in diets in developing countries less meat eaten , there high consumption of phytic acid beans , unleavened whole grain bread.

nonpolar antioxidants such eugenol—a major component of oil of cloves—have toxicity limits can exceeded misuse of undiluted essential oils. toxicity associated high doses of water-soluble antioxidants such ascorbic acid less of concern, these compounds can excreted rapidly in urine. more seriously, high doses of antioxidants may have harmful long-term effects. beta-carotene , retinol efficacy trial (caret) study of lung cancer patients found smokers given supplements containing beta-carotene , vitamin had increased rates of lung cancer. subsequent studies confirmed these adverse effects.

these harmful effects may seen in non-smokers, recent meta-analysis including data approximately 230,000 patients showed β-carotene, vitamin or vitamin e supplementation associated increased mortality saw no significant effect vitamin c. no health risk seen when randomized controlled studies examined together, increase in mortality detected when high-quality , low-bias risk trials examined separately. majority of these low-bias trials dealt either elderly people, or people disease, these results may not apply general population. meta-analysis later repeated , extended same authors, new analysis published cochrane collaboration; analysis confirmed previous results. these 2 publications consistent previous meta-analyzes suggested vitamin e supplementation increased mortality, , antioxidant supplements increased risk of colon cancer. beta-carotene may increase lung cancer. overall, large number of clinical trials carried out on antioxidant supplements suggest either these products have no effect on health, or cause small increase in mortality in elderly or vulnerable populations.

while antioxidant supplementation used in attempts prevent development of cancer, antioxidants may interfere cancer treatments, since environment of cancer cells causes high levels of oxidative stress, making these cells more susceptible further oxidative stress induced treatments. result, reducing redox stress in cancer cells, antioxidant supplements (and pharmaceuticals) decrease effectiveness of radiotherapy , chemotherapy. on other hand, other reviews have suggested antioxidants reduce side effects or increase survival times.