אין הוכחה חד-משמעית שאנטיאוקסידנטים מונעים סרטן

ואם כן, השפעתם קטנה הרבה יותר ממה שסברו בעבר. J Gen Intern Med. 2006 Jul;21(7):735-44 Antioxidants vitamin C AND vitamin e for the prevention AND treatment of cancer. OBJECTIVE: To evaluate the evidence of the supplements vitamin C AND vitamin E for treatment AND prevention of cancer. METHODS: Systematic review of trials AND meta-analysis. DATA SOURCES AND MAIN RESULTS: Thirty-eight studies showed scant evidence that vitamin C OR vitamin E beneficially affects survival. In the ATBC Cancer Prevention Study Group, no statistically significant effect of treatment was seen for any cancer individually, AND our pooled relative risk (regardless of tumor type) for alpha-tocopherol alone was 0.91 (95% confidence interval [CI]: 0.74, 1.12). All cause mortality was not significant. In the Linxian General Population Trial, the relative risks for cancer death for vitamin C (combined with molybdenum) was 1.06 (95% CI: 0.92, 1.21) AND for vitamin E (combined with beta-carotene AND selenium) was 0.87 (95% CI: 0.76, 1.00). We identified only 3 studies that reported statistically significant beneficial results: vitamin C (in combination with BCG) was found to be beneficial in a single trial of bladder cancer AND vitamin E (in combination with omega-3 fatty acid) increased survival in patients with advanced cancer. In the ATBC trial, in analyses of 6 individual cancers, the prevention of prostate cancer in subjects treated with alpha-tocopherol was statistically significant (RR=0.64, 95% CI: 0.44, 0.94). CONCLUSIONS: The systematic review of the literature does not support the hypothesis that the use of supplements of vitamin C OR vitamin E in the doses tested helps prevent and/or treat cancer in the populations tested. There were isolated findings of benefit, which require confirmation. ----------------------------------------------------------------------------- Ann Intern Med. 2006 Jul 31; The Efficacy AND Safety of Multivitamin AND Mineral Supplement Use To Prevent Cancer AND Chronic Disease in Adults: A Systematic Review for a National Institutes of Health State-of-the-Science Conference. BACKGROUND: Multivitamin AND mineral supplements are the most commonly used dietary supplements in the United States. PURPOSE: To synthesize studies on the efficacy AND safety of multivitamin/mineral supplement use in primary prevention of cancer AND chronic disease in the general population. DATA SOURCES: English-language literature search of the MEDLINE, EMBASE, AND Cochrane databases through February 2006 AND hand-searching of pertinent journals AND articles. STUDY SELECTION: Randomized, controlled trials in adults were reviewed to assess efficacy, AND randomized, controlled trials AND observational studies in adults OR children were reviewed to assess safety. DATA EXTRACTION: Paired reviewers extracted data AND independently assessed study quality. DATA SYNTHESIS: 12 articles from 5 randomized, controlled trials that assessed efficacy AND 8 articles from 4 randomized, controlled trials AND 3 case reports on adverse effects were identified. Study quality was rated fair for the studies on cancer, cardiovascular disease, cataracts, OR age-related macular degeneration AND poor for the studies on hypertension. In a poorly nourished Chinese population, combined supplementation with beta-carotene, alpha-tocopherol, AND selenium reduced the incidence of AND mortality rate from gastric cancer AND the overall mortality rate from cancer by 13% to 21%. In a French trial, combined supplementation with vitamin C, vitamin E, beta-carotene, selenium, AND zinc reduced the rate of cancer by 31% in men but not in women. Multivitamin AND mineral supplements had no significant effect on cardiovascular disease OR cataracts, except that combined beta-carotene, selenium, alpha-tocopherol, retinol, AND zinc supplementation reduced the mortality rate from stroke by 29% in the Linxian study AND that a combination of 7 vitamins AND minerals stabilized visual acuity loss in a small trial. Combined zinc AND antioxidants slowed the progression of advanced age-related macular degeneration in high-risk persons. No consistent adverse effects of multivitamin AND mineral supplements were evident. Limitations: Only randomized, controlled trials were considered for efficacy assessment. Special nutritional needs, such as use of folic acid by pregnant women to prevent birth defects, were not addressed. Findings may not apply to use of commercial multivitamin supplements by the general U.S. population. CONCLUSIONS: Evidence is insufficient to support the presence OR absence of benefits from use. ------------------------------------------------------------- Ann N Y Acad Sci. 2006 May;1067:22-6. The free radical fantasy: a panoply of paradoxes. Overly exuberant AND exaggerated past expectations AND claims of the free radical theory have been quieted by extensive randomized, double-blind, controlled human studies. A half century of data demonstrates its lack of predictability AND it has not been validated by the scientific method. Widespread use of antioxidants has failed to quell the current pandemic of cancer, diabetes, AND cardiovascular disease OR to stop OR reverse the aging process. Electronically modified oxygen derivatives contribute to the modulation of cellular redox status, which is of primary importance in disease prevention AND homeostasis. ------------------------------------------------------------------------ : Curr Pharm Des. 2006;12(5):599-613. Antioxidant vitamins AND risk of lung cancer. . Tobacco use is the leading risk factor for lung cancer, yet in addition to smoking habit, diet may also play a role in the disease's appearance. While there are reports to indicate that antioxidant vitamins AND carotenoids may decrease the risk of lung cancer, results to date have been somewhat ambiguous. This review aimed to describe the results yielded by different studies, which have addressed antioxidant vitamin intake AND lung cancer, AND to indicate the mechanisms whereby these nutrients might be exercising their activity. Antioxidant vitamins were observed to have no clear protective effect, though there was some evidence pointing to a protective role for vitamins C AND E. Vitamin A, in contrast, evinced no clear effect. Insofar as provitamin A carotenoids were concerned, lutein/zeaxanthin, lycopene AND alpha-carotene displayed a certain protective trend, yet beta-carotene exhibited no protective effect whatsoever; AND indeed, there was speculation as to whether it might even be pernicious in smokers. Beta-criptoxanthin, on the other hand, showed a more consistent protective effect. The study highlighted the need to conduct further research on smokers AND non-smokers alike, AND in particular, to investigate the effect, if any, on lung cancer of carotenoids OR vitamins when ingested in differing dosages.