Pence B C, Butler M J, Dunn D M, Miller M F, Zhao C, Landers M
Department of Pathology, Texas Tech University Health Sciences Center, Lubbock, USA.
Carcinogenesis. 1995 May;16(5):1157-60. doi: 10.1093/carcin/16.5.1157.
Recent epidemiologic studies have implicated red meat consumption as a risk factor for colon cancer in both men and women. However, it has been very difficult to separate the effects of meat as a protein source from the accompanying fat content of the diets analyzed in these studies. Experimental data from rodent feeding trials show mixed results, with no firm conclusions being possible in terms of the colon-cancer promoting effects of meat fat. The goal of the present study was to compare, in an experimental animal model, the effects of beef with casein as a protein source, within the context of a low- and high-fat diet containing either corn oil or beef tallow, on promotion of colon carcinogenesis. Tumors were induced in Sprague-Dawley rats with 1,2-dimethylhydrazine (20 mg/kg body wt for 10 weeks). Two hundred and eighty male weanling rats were randomized to eight dietary treatment groups of a 2x2x2 factorial design with fat source (corn oil vs. beef tallow), fat level (5% vs. 20%), and protein source (very lean beef vs. casein) as the factors. Diets were fed ad libitum before, during and after carcinogen treatment for a total of 27 weeks. At termination of the study, animals were examined for location, size and type of colon or extracolonic lesions. The total incidence and number of colon tumors were significantly lower in the groups fed beef rather than casein. High fat levels, regardless of source, significantly increased the number of colon adenomas. These results demonstrate that when lean beef is used as the protein source in the context of a low-fat diet, fewer intestinal tumors develop. These data do not support the belief that red meat consumption increases the risk for colon carcinogenesis, but underscores the importance of fat level in dietary context.
近期的流行病学研究表明，食用红肉是男性和女性患结肠癌的风险因素。然而，在这些研究中分析的饮食中，很难将肉类作为蛋白质来源的影响与伴随的脂肪含量的影响区分开来。啮齿动物喂养试验的实验数据显示结果不一，关于肉类脂肪对结肠癌的促进作用无法得出确凿结论。本研究的目的是在实验动物模型中，比较在含有玉米油或牛脂的低脂和高脂饮食背景下，以牛肉作为蛋白质来源与以酪蛋白作为蛋白质来源对结肠癌发生促进作用的影响。用1,2 - 二甲基肼（20毫克/千克体重，持续10周）诱导斯普拉格 - 道利大鼠产生肿瘤。280只雄性断奶大鼠被随机分为八个饮食处理组，采用2×2×2析因设计，因素包括脂肪来源（玉米油与牛脂）、脂肪水平（5%与20%）和蛋白质来源（极瘦牛肉与酪蛋白）。在致癌物处理前、处理期间和处理后随意喂食这些饮食，共27周。在研究结束时，检查动物结肠或结肠外病变的位置、大小和类型。喂食牛肉而非酪蛋白的组中，结肠肿瘤的总发生率和数量显著更低。无论来源如何，高脂肪水平都会显著增加结肠腺瘤的数量。这些结果表明，在低脂饮食中使用瘦牛肉作为蛋白质来源时，肠道肿瘤的发生较少。这些数据不支持食用红肉会增加结肠癌发生风险的观点，但强调了饮食中脂肪水平的重要性。
