בטה קרוטן עישון וסרטן ריאה

מחקרים עדכניים יותר ורבי היקף מגלים כי: במרביתם לא הוכח כי באנשים בריאים לקיחת תוספים מגינה מפני סרטן, במקצתם לקיחת תוספים מגינה מפני גידולים מסויימים ובאוכלוסיות מסויימות, ובמקצתם תוספים מעלים את שכיחות הסרטן והתמותה. להלן מספר מחקרים חדשים. (אמרנו כבר שרפואה זה לא מדע מדוייק). --------------------------------------------------------------------------------- J BUON. 2006 Jan-Mar;11(1):7-20. Nutritional aspects regarding lung cancer chemoprevention. Lung cancer is still one of the major causes of cancer-related deaths AND its mortality figures argue powerfully for new approaches to control this leading cancer threat. Chemoprevention can be defined as the use of specific agents to reverse, OR prevent premalignancy from progressing to invasive cancer. The use of foods AND dietary supplements present a safe chemopreventive strategy. Data for this review were identified by searches of PubMed AND references from relevant articles. Articles were identified by use of the search terms "lung cancer", "chemoprevention", "carcinogenesis", AND "retinoids". Only papers published in English were included. Trials in lung cancer chemoprevention have so far produced either neutral OR harmful primary endpoint results, whether in the primary, secondary, OR tertiary settings. Lung cancer was not prevented by beta-carotene, alpha-tocopherol, retinol, retinyl palmitate, N-acetylcysteine, OR isotretinoin in smokers. Ongoing trials may help define new avenues for chemoprevention. The concept of chemoprevention in lung cancer is still in its infancy, but in the future it may have a significant impact on the incidence AND mortality of lung cancer. In addition to epidemiologic studies, basic science research to detect mechanisms AND evaluate the chemopreventive potential of food components is necessary. The overwhelming evidence of a major role of nutrition in carcinogenesis, the many leads that nutritional intervention may reduce cancer incidence, AND the growth AND increasing sophistication of clinical trials networks point to a very promising future for nutritional intervention trials leading to substantial public benefit. ------------------------------------------------------------------------------------------- Cancer. 2007 Mar 1;109(5):891-8. Effects of alpha-tocopherol AND beta-carotene supplementation on upper aerodigestive tract cancers in a large, randomized controlled trial. Wright ME, Virtamo J, Hartman AM, Pietinen P, Edwards BK, Taylor PR, Huttunen JK, Albanes D. Division of Cancer Epidemiology AND Genetics, National Cancer Institute, NIH, DHHS, Bethesda, Maryland, USA. [email protected] BACKGROUND: Although smoking AND alcohol consumption are the major risk factors for upper aerodigestive tract cancers, observational studies indicate a protective role for fruits, vegetables, AND antioxidant nutrients. METHODS: The authors examined whether daily supplementation with 50 mg dl alpha-tocopheryl acetate and/or 20 mg beta-carotene reduced the incidence of OR mortality from oral/pharyngeal, esophageal, AND laryngeal cancers in the Alpha-Tocopherol, Beta-Carotene Cancer Prevention (ATBC) study, a double-blind, placebo-controlled primary prevention trial conducted in southwestern Finland. A total of 29,133 male smokers, aged 50-69 years AND free of cancer at baseline, were randomized in a 2 x 2 factorial design to the supplementation regimen for 5-8 years (median, 6.1 years). Incident cancers of the oral cavity AND pharynx (n = 65), esophagus (n = 24), AND larynx (n = 56) were identified through the Finnish Cancer Registry. Intervention effects were assessed using survival analysis AND proportional hazards models. RESULTS: There was no effect of either agent on the overall incidence of any upper aerodigestive tract cancer. For larynx, however, exploratory subgroup analyses were suggestive of a protective effect of beta-carotene supplementation on the incidence of early stage malignancies (stage I, relative risk [RR], 0.28, 95% confidence interval [CI]: 0.10-0.75). Neither agent affected mortality from these neoplasms. CONCLUSIONS: The results do not provide support for a protective effect of vitamin E OR beta-carotene supplementation on upper aerodigestive tract cancers, although beta-carotene supplementation may impact the incidence of some subtypes of laryngeal tumors. ------------------------------------------------------------------------------------------- 1: Am J Clin Nutr. 2007 Jan;85(1):314S-317S. Clinical trials of vitamin AND mineral supplements for cancer prevention . Greenwald P, Anderson D, Nelson SA, Taylor PR. Division of Cancer Prevention, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892-7309, USA. [email protected] Approximately 20-30% of Americans consume multivitamin supplements daily, indicating high public interest in the prevention of cancer AND other chronic diseases through a nutrition-based approach. Although several bioactive food components, including vitamins AND minerals, have been investigated for their ability to affect cancer risk, few large, randomized, placebo-controlled clinical trials of multivitamins with cancer as the primary endpoint have been performed. The results of most large-scale trials of multivitamin supplements (combinations of > OR = 2 vitamins AND minerals) to prevent cancer have been mixed. The Linxian General Population AND Dysplasia trials found a decreased risk of cancer, particularly stomach cancer, for participants taking a multivitamin supplement, but this was in a borderline-deficient population in China. Two trials, the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study AND the beta-Carotene AND Retinol Efficacy Trial, found an increased risk of lung cancer among male cigarette smokers OR asbestos-exposed persons taking beta-carotene-a surprising result, considering that most epidemiologic studies have suggested that consumption of fruit AND vegetables appears to lower cancer risk. To clarify the effects of multivitamin supplements, several large randomized clinical trials are underway, including the Physicians' Health Study II, the Selenium AND Vitamin E Cancer Prevention Trial, AND a European study, Supplémentation en Vitamines et Minéraux Antioxydants (SU.VI. MAX). Because epidemiologic studies generally evaluate foods rather than specific bioactive food components, a systematic approach to determining how combinations of vitamins AND minerals may interact to ameliorate cancer risk is necessary to further our understanding of the potential benefits AND risks of supplement use. --------------------------------------------------------------------------------------- 1: Int J Cancer. 2007 Mar 1;120(5):970-7. Prospective study of vitamins C, E, AND A AND carotenoids AND risk of oral premalignant lesions in men. Maserejian NN, Giovannucci E, Rosner B, Joshipura K. Department of Epidemiology, Harvard School of Public Health, Boston, MA, USA. [email protected] Case-control studies indicate that vitamins C, E, A AND carotenoids decrease risk of oral premalignant lesions (OPLs) AND oral cancer, but clinical trials have failed to find protective effects of beta-carotene AND suggest that vitamin E may increase risk. The authors prospectively evaluated the association between intake of vitamins C, E, A AND carotenoids AND incidence of OPL. Participants were 42,340 men in the Health Professionals Follow-up Study who provided information on supplement use AND diet every 2-4 years by food frequency questionnaire. The authors confirmed 207 clinically OR histopathologically diagnosed OPL events occurring between 1986 AND 2002 by medical record review. Multivariate-adjusted relative risks (RR) of OPL were calculated with proportional hazards models. Total intake of vitamin C, vitamin A OR carotenoids was not significantly associated with OPL risk. Dietary vitamin C was significantly associated with reduced risk (quintile 5 vs. 1, RR = 0.52, 95% CI 0.31-0.85, p(trend) = 0.04), but no association with supplemental vitamin C was observed. Inverse associations were apparent for beta-cryptoxanthin AND alpha-carotene intake. No clear relationship emerged with beta-carotene, lycopene OR lutein/zeaxanthin. Vitamin E was associated with increased risk (quintile 5 vs. 1, RR = 1.86, 95% CI 1.06-3.19), particularly among current smokers AND with supplemental intake (current-smokers, supplement dose tertile 3 vs. 1, RR = 3.07, 95% CI 1.28-7.34, p(trend) = 0.01). For current smokers, beta-carotene also increased risk. Vitamin C from dietary sources, but not supplements, was associated with a reduced risk of OPL. The observed increased risk for current smokers with high vitamin E OR beta-carotene intake should be explored further. ------------------------------------------------------------------------------- 1: Med Sci (Paris). 2006 Mar;22(3):319-20. Links [Beta-carotene is associated with lower risk of some cancers in women nonsmokers but with higher risk in women smokers] --------------------------------------------------------------------------- 1: J Natl Cancer Inst. 2005 Sep 21;97(18):1338-44. Dual Association of beta-carotene with risk of tobacco-related cancers in a cohort of French women. Touvier M, Kesse E, Clavel-Chapelon F, Boutron-Ruault MC. INSERM, Equipe E3N, Institut Gustave Roussy, 94805 Villejuif Cedex, France. BACKGROUND: Intervention studies have demonstrated that, in smokers, beta-carotene supplements had a deleterious effect on risk of lung cancer AND may have a deleterious effect on digestive cancers as well. We investigated a potential interaction between beta-carotene intake AND smoking on the risk of tobacco-related cancers in women. METHODS: A total of 59,910 women from the French Etude Epidémiologique de Femmes de la Mutuelle Générale de l'Education Nationale (E3N) prospective investigation were studied from 1994. After a median follow-up of 7.4 years, 700 women had developed cancers known to be associated with smoking. Diet, supplement use, AND smoking status at baseline were assessed by self-report. beta-carotene intake was classified into four groups: first (low intake), second, AND third tertiles of dietary intake, AND use of supplements (high intake). Unadjusted AND multivariable Cox proportional hazards models were used to calculate hazard ratios AND 95% confidence intervals (CIs) for cancer risk. All statistical tests were two-sided. RESULTS: Among never smokers, multivariable hazard ratios of all smoking-related cancers were 0.72 (95% CI = 0.57 to 0.92), 0.80 (95% CI = 0.64 to 1.01), AND 0.44 (95% CI = 0.18 to 1.07) for the second AND third tertiles of dietary intake, AND high beta-carotene intake, respectively, compared with low intake (Ptrend = .03). Among ever smokers, multivariable hazard ratios were 1.43 (95% CI = 1.05 to 1.96), 1.20 (95% CI = 0.86 to 1.67), AND 2.14 (95% CI = 1.16 to 3.97) for the second AND third tertiles of dietary intake, AND high beta-carotene intake, respectively, compared with low intake (Ptrend = .09). Tests for interaction between beta-carotene intake AND smoking were statistically significant (Ptrend =.017). In this population, the absolute rates over 10 years in those with low AND high beta-carotene intake were 181.8 AND 81.7 cases per 10,000 women in never smokers AND 174.0 AND 368.3 cases per 10,000 women in ever smokers. CONCLUSIONS: beta-carotene intake was inversely associated with risk of tobacco-related cancers among nonsmokers with a statistically significant dose-dependent relationship, whereas high beta-carotene intake was directly associated with risk among smokers.