Baradaran, Azar.

Rafieian, Morteza.

Rafieian-Kopaei, Mahmoud.

PubMed

shahrekord university of medical scinces

Journal of Research in Medical Sciences| July 2013 | 628Mahmoud Rafieian‑Kopaei, Azar Baradaran1, Morteza RafieianMedical Plants Research Center, Shahrekord University of Medical Sciences, Shahrekord, 1Department of Pathology, Isfahan University of Medical Sciences, Isfahan, IranAddress for correspondence: Prof. Mahmoud Rafieian‑Kopaei, Medical Plants Research Center, Shahrekord University of Medical Sciences, Shahrekord, Iran. E‑mail: rafieian@yahoo.comREFERENCES1. Halliwell B. Free radicals and antioxidants: Updating a personal view. Nutr Rev 2012;70:257‑65.2. Rafieian‑Kopaei M, Baradaran A, Rafieian M. Plants antioxidants: From laboratory to clinic. J Nephropathology 2013;2:152‑3.3. Minaiyan M, Ghannadi AR, Mahzouni P, Abed AR. Preventive effect of Cichorium Intybus L. Two extracts on cerulein‑induced acute pancreatitis in mice. Int J Prev Med 2012;3:351‑7.4. Tabesh M, Hariri M, Askari G, Ghiasvand R, Tabesh M, Heydari A, et al. The relationship between vegetables and fruits intake and glycosylated hemoglobin values, lipids profiles and nitrogen status in type II inactive diabetic patients. Int J Prev Med 2013;4 (Suppl 1):S63‑7.5. Sahni N, Gupta KL. Dietary antioxidants and oxidative stress in predialysis chronic kidney disease patients. J Nephropatholology 2012;1:134‑42.6. Vafa MR, Haghighatjoo E, Shidfar F, Afshari S, Gohari MR, Ziaee A. Effects of apple consumption on lipid profile of hyperlipidemic and overweight men. Int J Prev Med 2011;2:94‑100.7. Tavafi M. Diabetic nephropathy and antioxidants. J Nephropatholology 2013;2:20‑7.8. Nasri H, Nematbakhsh M, Ghobadi S, Ansari R, Shahinfard N, Rafieian‑Kopaei M. Preventive and curative effects of ginger extract against histopathologic changes of gentamicin‑induced tubular toxicity in rats. Int J Prev Med 2013;4:316‑21.9. Solati M, Mahboobi HR. Paraoxonase enzyme activity and dyslipidemia in chronic kidney disease patients. J Nephropatholology 2012;1:123‑5.10. Rafieian‑Kopaei M, Nasri H, Nematbakhsh M, Baradaran A, Gheissari A, RouhiH, et al. Erythropoietin ameliorates genetamicin‑induced renal toxicity: A biochemical and histopathological study. J Nephropatholology 2012;1:109‑16.11. Baillie JK, Thompson AA, Irving JB, Bates MG, Sutherland AI, Macnee W, et al. Oral antioxidant supplementation does not prevent acute mountain sickness: Double blind, randomized placebo‑controlled trial. QJM 2009;102:341‑8.12. Khajehdehi P. Turmeric: Reemerging of a neglected Asian traditional remedy. J Nephropatholology 2012;1:17‑22.13. Minaiyan M, Mostaghel E, Mahzouni P. Preventive therapy of experimental colitis with selected iron chelators and anti‑oxidants. Int J Prev Med 2012;3(Suppl 1):S162‑9.14. Bjelakovic G, Nikolova D, Gluud LL, Simonetti RG, Gluud C. Mortality in randomized trials of antioxidant supplements for primary and secondary prevention: Systematic review and meta‑analysis. JAMA 2007;297:842‑57.15. Mohanty P, Hamouda W, Garg R, Aljada A, Ghanim H, Dandona P. Glucose challenge stimulates reactive oxygen species (ROS) generation by leucocytes. J Clin Endocrinol Metab 2000;85:2970‑3.Oxidative stress and the paradoxical effects of antioxidantsSir,Oxidative stress is referred to imbalance between the reactive oxygen species and antioxidants system to detoxify the reactive intermediates or to repair the resulting damage.[1‑3] Oxidation is a chemical reaction that transfers electrons or hydrogen from a substance to an oxidizing agent.[4‑6] Although oxidation reactions are crucial for life, they can also be damaging.[1,2,7‑9] Insufficient levels of antioxidants or inhibition of the antioxidant enzymes, cause oxidative stress which may damage all components of the cell, including proteins, lipids and deoxyribonucleic acid.[1] The oxidative stress is thought to be involved in the development of atherosclerosis, heart failure, myocardial infarction, cancer, Parkinson’s disease, Alzheimer’s disease, sickle cell disease, lichen planus, vitiligo, autism, chronic fatigue syndrome and renal failure.[1,2,6,10‑14] Antioxidants are reducing agents such as thiols, ascorbic acid, or polyphenols molecules that inhibit the oxidation of other molecules by being oxidized themselves. Plants and animals maintain complex systems of multiple types of antioxidants such as glutathione, vitamin C, vitamin A and vitamin E as well as enzymes such as catalase, superoxide dismutase and various peroxidases.[1,2,6,13] Antioxidants are widely used in dietary supplements and have been investigated for the prevention of diseases such as cancer, coronary heart disease and even altitude sickness. Although initial studies suggested that antioxidant supplements might promote health, later large clinical trials with a limited number of antioxidants detected no benefit and even suggested that excess supplementation with certain putative antioxidants may be harmful.[11,14] From the literature review we may conclude that the diets high in antioxidants (fruits and vegetables) are nearly almost beneficial, but this is not the case for diet supplementations. The possible explanation is that, in the diet, there is a mix of antioxidants and it is well recognized that they work as a continuous chain, while supplementation is usually given using one or two substances. Therefore, the antioxidant chain is not completely available.[1,2,6,13] In this regard, it is well‑known that after scavenging free radicals, if an antioxidant is not restored by the following antioxidant in the chain, it begins to be a pro‑oxidant. In this situation, the final effect of such supplementations would be no effect or a damaging effect.[14,15] Therefore, in antioxidant therapy complimentary antioxidants cannot always substitute the fruits and vegetables high in antioxidants. letter tO editOr

Oxidative stress and the paradoxical effects of antioxidants

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