Continuing low colon cancer incidence in African populations
Continuing low colon cancer incidence in African populations
复制标题
非洲人群结肠癌发病率持续较低
DOI：
10.1111/j.1572-0241.2000.01922.x
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发表时间：
2000
影响因子：
9.8
通讯作者：
A. Walker
中科院分区：
文献类型：
--
作者：
I. Segal;C. Edwards;A. Walker
在发展中人口的所有大城市中，环境因素（饮食结构、体力活动、吸烟习惯、饮酒和压力）正在发生变化。与此同时，健康/不健康的模式也发生了变化。在南非，除了幼儿发病率和死亡率大幅下降外，非洲城市人口在女性肥胖、高血压和糖尿病患病率方面也领先于白人 (1)。然而，与此形成鲜明对比的是，结肠疾病——憩室病、炎症性肠病和结直肠癌的发病率却发生了微小的变化。此外，大多数结直肠癌的前兆结直肠息肉几乎不存在 (2, 3)。每10万人的年龄标化结直肠癌发病率为2.2；当地白人的比例为 18.7 (4)。然而在非裔美国人中，仅结肠癌的发病率就高达 32.8，几乎是世界上最高的 (5)。据报道，当地非洲人的肠道行为发生了变化，包括粪便重量、排便频率和整个肠道传输时间，尽管粪便 pH 值没有变化 (6, 7)。现在的值介于之前在农村人口中观察到的值和在西方人口中报告的值之间。非洲城市人的膳食纤维摄入量已从约 25-35 克（两代人前）减少到每天 15-20 克 (8)。主粮谷物仍然是玉米粉；然而，它通常是精炼的（约70%的提取率）。面包的摄入量有所增加，但这主要是白面包。另外，由于成本原因，蔬菜和水果的食用量相对较低，每天大约2、5份；也就是说，饮食中的抗氧化剂含量较低。然而，非常重要的是，尽管玉米粉的膳食纤维含量有所下降，但其“抗性”淀粉含量仍然很高，为 18 克/100 克 (9)。抗性淀粉发酵比膳食纤维发酵产生更多的丁酸 (10)。丁酸被认为可以通过刺激癌细胞凋亡、分化和抑制结肠癌细胞侵袭来降低癌症风险 (10)。
In all big towns and cities in developing populations there are ongoing transitions in environmental factors—in dietary composition, physical activity, smoking practice, alcohol consumption, and stress. Contemporaneously, changes have occurred in the patterns of health/ill-health experienced. In South Africa, apart from major falls in the morbidity and mortality of young children, the urban African population has raced ahead of the white population in respect to the prevalence of obesity in women, hypertension, and diabetes (1). Yet, in remarkable contrast, minimal changes have occurred in the incidence of colonic diseases—diverticular disease, inflammatory bowel disease, and colorectal cancer. Furthermore, colorectal polyps, the precursor of most colorectal cancers, are nearly absent (2, 3). The age-standardized incidence rate per 100,000 population for colorectal cancer is 2.2; it is 18.7 for the local white population (4). Yet in African-Americans, the incidence rate of colon cancer alone, 32.8, is almost the highest in the world (5). There have been reports of alterations in bowel behavior in local Africans, in regard of stool weight, defecation frequency, and whole gut transit time, although not fecal pH value (6, 7). Values are now intermediate between those previously observed in rural populations, and such reported in western populations. The dietary fiber intake of urban Africans has decreased from approximately 25–35 g (two generations ago) to 15–20 g daily (8). The staple cereal remains maize meal; however, it is usually refined (about 70% extraction rate). The intake of bread has increased, but this is mainly white bread. Additionally, because of their costs, consumption of vegetables and fruit are relatively low, about 2, 5 helpings daily; ie., the diet is low in antioxidants. Yet, very importantly, although the dietary fiber content of maize meal has fallen, its content of “resistant” starch remains high, at 18 g/100 g (9). Resistant starch fermentation produces more butyric acid than the fermentation of dietary fiber (10). Butyric acid is believed to reduce cancer risk by stimulating apoptosis, differentiation of cancer cells, and by inhibiting colon cancer cell invasion (10).