PHYSIOLOGICAL EFFECTS OF VEGETABLE AND CEREAL FIBER

许多流行病学证据支持膳食纤维是 防止结肠癌发生。 然而，最近的研究发现， 植物纤维与减少结肠癌有关 而谷物纤维则没有。 生理效应研究 膳食纤维的使用产生了混合的结果和潜力 纤维在结肠癌预防中的作用机制仍然存在 晦涩难懂。 此外，有证据表明， 一般来说，饮食和纤维的影响在以下方面不同： 性别 结肠癌的发病率在年轻女性中高于 年轻人，更多的女性比男性呼吸甲烷排泄物 便秘和缓慢通过时间在 妇女 因此，拟议研究的总体目标是 研究两种膳食纤维来源的命运差异， 控制饮食的健康男女 既 蔬菜和谷物纤维将在2个水平，10克和30 每日膳食纤维克，代表当前纤维的水平 美国公众的纤维摄入量和推荐摄入量。 呼吸甲烷排泄物和非甲烷排泄物都将 选择参加，因为呼吸甲烷排泄已经 与结肠癌有关 首先收集数据， 消耗他们的习惯饮食，然后受试者将消耗5个测试 随机顺序的饮食：1）无纤维; 2）+10 g/d膳食纤维（DF） 3）+30 g/d DF作为谷物纤维; 4）+10 g/d DF作为谷物纤维; 植物纤维：5）添加30 g/d DF作为植物纤维。 在所有饮食中，胃肠道功能的指标，包括 粪便重量、全肠道通过时间和呼吸氢 在受试者接受以下治疗后，将测量排泄1周 食用规定的饮食2周。 呼吸甲烷， 将测量粪便pH值，因为两者均显示为 在结肠癌患者中更高。 中性洗涤剂消化率 纤维及其碳水化合物成分将被定量为 测量纤维分解，以及粪便挥发性脂肪酸， 粪胆汁酸和中性固醇排泄。 最后，钙， 镁、铁平衡和矿物质的血液指标 状态将被测量，以确定是否30克膳食纤维 每天都会破坏矿物质平衡。

Much epidemiological evidence supports that dietary fiber is protective against colon carcinogenesis. Yet, recent studies find that vegetable fiber is associated with decreased colon cancer risk while cereal fiber is not. Studies on the physiological effects of dietary fiber have yielded mixed results and potential mechanisms of fiber's role in colon cancer prevention remain obscure. Furthermore, there is evidence that the metabolic effects of diet in general and fiber in particular differ between the sexes. Colon cancer incidence is higher in young women than young men, more women are breath methane excretors than men and constipation and slow transit time are more common in women. Thus, the overall objective of the proposed research is to examine differences in the fate of two dietary fiber sources in healthy men and women consuming controlled diets. Both a vegetable and cereal fiber will be fed at 2 levels, 10 grams and 30 grams of dietary fiber daily, levels representing current fiber intakes and recommended fiber intakes for the American public. Both breath methane excretors and non-methane excretors will be chosen to participate since breath methane excretion has been linked to colon cancer. Data will first be collected while subjects consume their habitual diets and then subjects will consume 5 test diets in random order: 1) fiber-free; 2) +10 g/d dietary fiber (DF) as cereal fiber; 3) +30 g/d DF as cereal fiber; 4) +10 g/d DF as vegetable fiber; 5) +30 g/d DF as vegetable fiber. On all diets, indicators of gastrointestinal function, including stool weight, whole gut transit time, and breath hydrogen excretion will be measured for 1 week after subjects have consumed the defined diets for 2 weeks. Breath methane and fecal pH will be measured since both have been shown to be higher in colon cancer patients. Digestibility of neutral detergent fiber and its carbohydrate components will be quantitiated as a measure of fiber breakdown, as will fecal volatile fatty acids, fecal bile acid and neutral sterol excretion. Finally, calcium, magnesium, and iron balances and blood indicators of mineral status will be measured to determine if 30 grams of dietary fiber daily will upset mineral balance.