Kunzmann Andrew T, Coleman Helen G, Huang Wen-Yi, Kitahara Cari M, Cantwell Marie M, Berndt Sonja I
Centre for Public Health, Queen's University Belfast, Northern Ireland, and.
Centre for Public Health, Queen's University Belfast, Northern Ireland, and
Am J Clin Nutr. 2015 Oct;102(4):881-90. doi: 10.3945/ajcn.115.113282. Epub 2015 Aug 12.
Dietary fiber has been associated with a reduced risk of colorectal cancer. However, it remains unclear at which stage in the carcinogenic pathway fiber may act or which food sources of dietary fiber may be most beneficial against colorectal cancer development.
The objective was to prospectively evaluate the association between dietary fiber intake and the risk of incident and recurrent colorectal adenoma and incident colorectal cancer.
Study participants were identified from the intervention arm of the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial. Participants received flexible sigmoidoscopy at baseline and 3 or 5 y after. Dietary fiber intake was measured by using a self-reported dietary questionnaire. The colorectal cancer, incident adenoma, and recurrent adenoma analyses were based on 57,774, 16,980, and 1667 participants, respectively. Unconditional logistic regression was used to assess the risk of incident and recurrent adenoma, and Cox proportional hazards models were used to assess the risk of colorectal cancer across categories of dietary fiber intake, with adjustment for potential confounders.
Elevated total dietary fiber intake was associated with a significantly reduced risk of incident distal colorectal adenoma (ORhighest vs. lowest tertile of intake: 0.76; 95% CI: 0.63, 0.91; P-trend = 0.003) but not recurrent adenoma (P-trend = 0.67). Although the association was not statistically significant for colorectal cancer overall (HR: 0.85; 95% CI: 0.70, 1.03; P-trend = 0.10), a reduced risk of distal colon cancer was observed with increased total fiber intake (HR: 0.62; 95% CI: 0.41, 0.94; P-trend = 0.03). Protective associations were most notable for fiber originating from cereals or fruit.
This large, prospective study within a population-based screening trial suggests that individuals consuming the highest intakes of dietary fiber have reduced risks of incident colorectal adenoma and distal colon cancer and that this effect of dietary fiber, particularly from cereals and fruit, may begin early in colorectal carcinogenesis. This trial was registered at clinicaltrials.gov as NCT01696981.
膳食纤维与降低结直肠癌风险有关。然而，膳食纤维在致癌途径的哪个阶段发挥作用，或者哪种膳食纤维的食物来源对预防结直肠癌的发生可能最为有益，目前仍不清楚。
前瞻性评估膳食纤维摄入量与新发及复发性结直肠腺瘤风险以及新发结直肠癌风险之间的关联。
研究参与者来自前列腺、肺、结直肠和卵巢癌筛查试验的干预组。参与者在基线时以及3年或5年后接受乙状结肠镜检查。膳食纤维摄入量通过自我报告的饮食问卷进行测量。结直肠癌、新发腺瘤和复发性腺瘤分析分别基于57774名、16980名和1667名参与者。采用无条件逻辑回归评估新发和复发性腺瘤的风险，采用Cox比例风险模型评估不同膳食纤维摄入量类别下结直肠癌的风险，并对潜在混杂因素进行调整。
总膳食纤维摄入量增加与新发远端结直肠腺瘤风险显著降低相关（摄入量最高三分位数与最低三分位数相比的比值比：0.76；95%置信区间：0.63，0.91；P趋势 = 0.003），但与复发性腺瘤无关（P趋势 = 0.67）。尽管总体上膳食纤维与结直肠癌的关联无统计学意义（风险比：0.85；95%置信区间：0.70，1.03；P趋势 = 0.10），但随着总膳食纤维摄入量增加，远端结肠癌风险降低（风险比：0.62；95%置信区间：0.41，0.94；P趋势 = 0.03）。谷类或水果来源的膳食纤维的保护作用最为显著。
在一项基于人群的筛查试验中的这项大型前瞻性研究表明，膳食纤维摄入量最高的个体新发结直肠腺瘤和远端结肠癌的风险降低，并且膳食纤维的这种作用，尤其是来自谷类和水果的膳食纤维，可能在结直肠癌发生的早期就开始起作用。该试验在clinicaltrials.gov上注册，注册号为NCT01696981。
