Rock Cheryl L
Department of Family and Preventive Medicine and Cancer Prevention and Control Program, University of California, San Diego, La Jolla 92093-0901, USA.
Recent Results Cancer Res. 2007;174:171-7. doi: 10.1007/978-3-540-37696-5_14.
Colorectal cancer is a major cause of morbidity in developed countries, and epidemiological and experimental research suggests that environmental factors, particularly diet, may play a key etiologic role. Among the various dietary factors that have been proposed to affect the risk and progression of colon cancer, dietary fiber has been of greatest interest, due to the effects of fiber on the function of the large bowel. Dietary fiber is a heterogeneous group of compounds, consisting of the remnants of plant cells resistant to hydrolysis by human alimentary enzymes. Several case-control studies and a few cohort studies have linked higher fiber intake to reduced risk for colorectal cancer, although the results of these observational studies have been inconsistent. In the large European Prospective Investigation into Cancer and Nutrition observational study, higher dietary fiber from foods was associated with an estimated 25% reduction in risk for large bowel cancer. However, no significant relationship between fiber intake (or major food sources of fiber) and risk for colorectal cancer was observed in a recently reported large pooled analysis of several cohort studies. Well-known limitations of observational studies, particularly relating to the collection and interpretation of dietary data, constrain conclusions from these studies. To date, intervention studies testing the relationship between dietary fiber and colon cancer have focused on whether fiber supplementation or diet modification can affect the risk for adenoma recurrence and growth in individuals with a history of adenomatous polyps. In four of these intervention studies, subjects in the intervention arm were prescribed dietary fiber supplements, and beneficial effects on adenoma recurrence were not observed over 3-5 years of follow-up. In a large randomized U.S. study, the Polyp Prevention Trial, the effect of prescribing diet modification (increased fiber and reduced fat intakes) was tested, and no effects on adenoma recurrence were observed, although dietary biomarker data suggest that the change in dietary intakes in the intervention arm was not substantial. The effect of increased dietary fiber intake on risk for colorectal cancer has not been adequately addressed in studies conducted to date. Longer-term trials and higher levels of fiber intake are strategies that have been suggested to increase knowledge in this area. Also, laboratory and clinical studies that continue to provide insight into biological mechanisms may help to better target intervention efforts.
在发达国家，结直肠癌是发病的主要原因之一，流行病学和实验研究表明，环境因素，尤其是饮食，可能起着关键的病因学作用。在诸多被认为会影响结肠癌风险和进展的饮食因素中，膳食纤维最受关注，因为它对大肠功能有影响。膳食纤维是一组异质化合物，由人体消化酶难以水解的植物细胞残余物组成。多项病例对照研究和一些队列研究将较高的纤维摄入量与降低结直肠癌风险联系起来，尽管这些观察性研究的结果并不一致。在大型欧洲癌症与营养前瞻性调查观察性研究中，食物中较高的膳食纤维摄入量与估计降低25%的大肠癌风险相关。然而，在最近一项对多项队列研究的大型汇总分析中，未观察到纤维摄入量（或纤维的主要食物来源）与结直肠癌风险之间存在显著关系。观察性研究存在众所周知的局限性，尤其是在饮食数据的收集和解释方面，这限制了这些研究得出的结论。迄今为止，检验膳食纤维与结肠癌关系的干预性研究主要集中在纤维补充或饮食调整是否会影响有腺瘤性息肉病史个体的腺瘤复发和生长风险。在其中四项干预性研究中，干预组的受试者被规定服用膳食纤维补充剂，在3至5年的随访中未观察到对腺瘤复发的有益影响。在美国一项大型随机研究——息肉预防试验中，测试了规定饮食调整（增加纤维摄入量和减少脂肪摄入量）的效果，未观察到对腺瘤复发有影响，尽管饮食生物标志物数据表明干预组的饮食摄入量变化不大。迄今为止，关于增加膳食纤维摄入量对结直肠癌风险的影响在已开展的研究中尚未得到充分探讨。有人建议采用长期试验和更高水平的纤维摄入量来增加该领域的知识。此外，持续深入了解生物学机制的实验室和临床研究可能有助于更好地确定干预措施的目标。
