膳食纤维与结肠癌关系研究

结肠癌目前呈逐年上升趋势,而膳食纤维能降低患结肠癌风险性;近年随着研究不断深入,出现许多不同观点,有些观点甚至认为膳食纤维能增加患结肠癌风险性。该文介绍膳食纤维与结肠癌之间关系及可能性机理,并进行分析。     

Diet, nutrition, and cancer

Evidence pertaining to the role of dietary factors in carcinogenesis comes from both epidemiological studies and laboratory experiments. In 1982, the Committee on Diet, Nutrition, and Cancer of the National Research Council conducted a comprehensive evaluation of this evidence. That assessment as well as recent epidemiological and laboratory investigations suggest that a high fat diet is associated with increased susceptibility to cancer of different sites, particularly the breast and colon, and to a lesser extent, the prostate. Current data permit no definitive conclusions about other dietary macroconstituents including cholesterol, total caloric intake, protein, carbohydrates and total dietary fiber. Specific components of fiber, however, may have a protective effect against colon cancer. In epidemiological studies, frequent consumption of certain fruits and vegetables, especially citrus fruits and carotene-rich and cruciferous vegetables, is associated with a lower incidence of cancers at various sites. The specific components responsible for these effects are not clearly identified, although the epidemiological evidence appears to be most consistent for a protective effect of carotene on lung cancer and less so for vitamins A and C and various cancer sites. The laboratory evidence is most consistent for vitamin A deficiency and enhanced tumorigenesis, and for the ability of various nonnutritive components in cruciferous vegetables to block in-vivo carcinogenesis. The data for minerals and carcinogenesis are extremely limited, although preliminary evidence from both epidemiological and laboratory studies suggests that selenium may protect against overall cancer risk. Frequent consumption of cured, pickled, or smoked foods, possibly because they may contain nitrosamines or polycyclic aromatic hydrocarbons, appears to increase the risk of esophageal or stomach cancer, however, the specific causative agents in these foods are not clearly identified. Excessive alcohol consumption among smokers appears to be associated with an elevated risk of cancers of the oral cavity, esophagus, larynx, and respiratory tract. The mechanisms of action of dietary factors on carcinogenesis are poorly understood. The NRC committee, and more recently, the National Cancer Institute and the American Cancer Society have proposed interim dietary guidelines to lower the risk of cancer. These guidelines are consistent with general dietary recommendations proposed by U.S. government agencies for maintenance of good health.(ABSTRACT TRUNCATED AT 400 WORDS)     

Nutritional aspects of colon cancer

During the last decade, a substantial amount of progress has been made in the understanding of the relationship between the dietary constituents and the development of colon cancer in man. The information base is sufficiently convincing with respect to an enhancing effect as a function of total fat intake and a protective effect of certain dietary fibers in colon cancer. The populations with high incidence of colon cancer are characterized by consumption of high-dietary fat which may be a risk factor in the absence of factors that are protective, such as use of whole-grain cereals, high fibrous foods and vegetables mainly of cruciferous type. Application of the findings made thus far in colon cancer research for the general public is, therefore, to have a far-reaching impact on the major premature, killing diseases in the western world.     

Modulation of the human gut microbiota by phenolics and phenolic fiber‐rich foods

The gut microbiota plays a prominent role in human health. Alterations in the gut microbiota are linked to the development of chronic diseases such as obesity, inflammatory bowel disease, metabolic syndrome, and certain cancers. We know that diet plays an important role to initiate, shape, and modulate the gut microbiota. Long‐term dietary patterns are shown to be closely related with the gut microbiota enterotypes, specifically long‐term consumption of carbohydrates (related to Prevotella abundance) or a diet rich in protein and animal fats (correlated to Bacteroides). Short‐term consumption of solely animal‐ or plant‐based diets have rapid and reproducible modulatory effects on the human gut microbiota. These alterations in microbiota profile by dietary alterations can be due to impact of different dietary macronutrients, carbohydrates, protein, and fat, which have diverse modulatory effects on gut microbial composition. Food‐derived phenolics, which encompass structural variants of flavonoids, hydroxybenzoic acids, hydroxycinnamic acids, coumarins, stilbenes, ellagitannins, and lignans can modify the gut microbiota. Gut microbes have been shown to act on dietary fibers and phenolics to produce functional metabolites that contribute to gut health. Here, we discuss recent studies on the impacts of phenolics and phenolic fiber‐rich foods on the human gut microbiota and provide an insight into potential synergistic roles between their bacterial metabolic products in the regulation of the intestinal microbiota.     

Resistant starch and “the butyrate revolution”

Early epidemiological studies indicated that populations that consume a high proportion of non-starch polysaccharide (NSP) dietary fibre (DF) in their daily diet suffer less from gastrointestinal diseases, in particular colorectal cancers, than populations that consume diets that are high in fat and protein but low in NSP fibre. In this respect, diet, by increasing the amount of vegetables and NSP DF's, has been suggested to contribute as much as 25–35% to risk reduction for colorectal cancer. A reduction of fat intake may further reduce the risk by 15–25%. Based on these observations, DF's and substances that are part of the fibre complex such as antioxidants, flavonoids, sulphur containing compounds and folate have been proposed as potentially protective agents against colon cancer. However, results from controlled prospective studies in which beta-carotene and vitamin E or isolated dietary fibres were given to high risk groups showed disappointing results. There are recent indications that the regular consumption of certain subclasses of highly fermentable dietary fibre sources result in gut associated immune and flora modulation as well as a significant production of short chain fatty acids. In vitro studies as well as animal studies indicate that in particular propionate and butyrate have the potential to support the maintenance of a healthy gut and to reduce risk factors that are involved in the development of gut inflammation as well as colorectal cancer. A suggestion put forward is that beneficial effects may be obtained in particular by the consumption of resistant starch (RS) because of the high yield of butyrate and propionate when fermented. These SCFA are the prime substrates for the energy metabolism in the colonocyte and they act as growth factors to the healthy epithelium. In normal cells butyrate has been shown to induce proliferation at the crypt base, enhancing a healthy tissue turnover and maintenance. In inflamed mucosa butyrate stimulates the regeneration of the diseased lining of the gut. In neoplastic cells butyrate inhibits proliferation at the crypt surface, the site of potential tumour development. Moreover, models of experimental carcinogenesis in animals have shown the potential to modify a number of metabolic actions and steps in the cell cycle in a way that early events in the cascade of cancer development may be counteracted while stages of progression may be slowed down. The present review highlights a number of these aspects and describes the metabolic and functional properties of RS and butyrate.     

膳食营养素与炎症性肠病关系研究进展

炎症性肠病（inflammation bowel disease,IBD）是一组以肠道炎症性细胞浸润、肠黏膜受损为主要表现的肠道慢性炎症病变,包括溃疡性结肠炎和克罗恩氏病。流行病学调查结果显示,高脂摄入增加IBD的发病风险,IBD的发病率与居民动物蛋白摄入量的增加有一定的关联性,膳食纤维摄入量与IBD发病率呈负相关。IBD的发病机制复杂,主要包括遗传因素和环境因素,其中饮食是重要的环境因素之一;目前膳食营养干预是防治IBD的有效策略。本文综述了近年来膳食脂肪、蛋白质、碳水化合物三大营养素对IBD发病机制影响方面的研究,并从膳食营养素的角度综合分析了IBD的饮食干预治疗策略。     

乳制品和钙摄入量对人体和动物体重及体成分的影响

膳食调查、动物实验和某些人体研究初步证明，在除去膳食总热量的影响之后，膳食钙是一个影响体重和体脂肪含量的独立因素。高脂肪、高糖、低钙膳食促进体脂肪的合成，而在同样的热能摄入量下，膳食钙摄入量的增加，特别是酸奶和其他乳制品的摄入量，与体脂肪比例和体重呈负相关关系。关于钙摄入、胞外钙浓度与胰岛素分泌和体脂肪代谢调控作用的理论已经初步建立。动物实验表明，仅用无机钙补充剂不能与摄入乳制品达到同样的体重控制效果，因此认为乳制品中存在的其他活性成分，以及乳制品中的蛋白质与碳水化合物比例也在减少脂肪积累和控制体重方面有重要作用。     

Whole grains — impact of consuming whole grains on physiological effects of dietary fiber and starch

Much of the present research on the physiological effects of dietary fiber and starch has been done on sources isolated from the parent material, and it is not clear whether they have the same effects if fed in the intact or whole grain. For dietary fiber, physiological effect depends on extent of fermentation in the large intestine, and this is influenced by chemical composition, solubility, physical form, and presence of lignin or other compounds. All of these factors are altered by isolation of a fiber source from the whole grain, and hence effects of eating fiber vary. Similarly, physical form and presence in the whole grain will affect digestibility of starch in the small intestine, which in turn influences the glycemic response and colonic effects determined by the extent of malabsorption and entry into the colon. Starch that enters the colon is fermented and produces short‐chain fatty acids, particularly butyrate, which is necessary to maintain a healthy mucosa. Hence, their presence within the whole grain may have important implications for health for both dietary fiber and starch. Evidence indicates that such effects are beneficial and that whole‐grain consumption should be encouraged.     

Epidemiological evidence for the impact of whole grains on health

Current dietary advice suggests consumers increase consumption of whole‐grain products because of their potential role in prevention of chronic disease. Whole grains are important sources of nutrients that are in short supply in our diet, including dietary fiber, resistant starch, trace minerals, certain vitamins, and other compounds of interest in disease prevention, including phytoestrogens and antioxidants. Despite dietary recommendations to increase intake of whole grains, little epidemiological evidence is available to support the physiological importance of whole‐grain intake. Most epidemiological studies focus on nutrients, rather than whole foods, so little attempt has been made to evaluate the contribution of whole grains in disease. Further, studies on vegetarians that show decreased risk of degenerative diseases are unable to separate the contribution of fruit and vegetable intake when compared with whole‐grain intake and protection from disease. The few epidemiological studies that have evaluated a role for whole grains suggest that they may have an important role in disease prevention and deserve more study.     

Taioba (Xanthosoma sagittifolium) Leaves: Nutrient Composition and Physiological Effects on Healthy Rats

Several studies have shown that fruits and vegetables contribute to protect against degenerative pathologies such as cardiovascular diseases, diabetes, and cancer, mainly due to the presence of dietary fiber (DF) and polyphenols. Taioba (Xanthosoma sagittifolium) is an edible aroid widely grown in many parts of Africa, America, and Asia. The tubers portions of taioba are widely consumed; however, the leafy portions are generally discarded, despite their high nutritive value. In this study, we have partly characterized the DF of lyophiized taioba leaf (LTL), and assessed the possible protective effects on biochemical parameters and on bile acid (BA) production in colon and cecum, when fed to healthy rats for 4 wk. Forty‐five Wistar rats were assigned to either of 5 groups: group 1 received AIN 93G diet (CG: Control); group 2 received AIN 93G containing 2.5% of cellulose + 2.5% inulin (CEIN_5%); group 3 received AIN 93G containing 2.5% of cellulose + 2.5% taioba fiber (CETA_5%); group 4 received AIN 93G containing 5% cellulose + 2.5% taioba fiber (CETA_7.5%); group 5 received AIN 93G containing 5% cellulose + 2.5% of inulin (CEIN_7.5%). LTL showed high contents of total fiber, predominantly comprising insoluble DF with glucose as the major monomer. Rats receiving LTL had increased fecal mass and fat excretion, and improved BA profiles by diminishing the proportion of secondary acids, thus suggesting that consumption of taioba leaf may have the property of lowering the risk of colon cancer.     

Correlations of dietary patterns with prostate health

Both genetic and environmental influences may be involved in etiology of prostate health and prostate cancer. These include ethnic origin, family history, smoking, and diet. Adiposity and excess energy intake are potentially distinct risk factors and positive associations with prostate cancer risk for both were observed among case-control and cohort studies. Some epidemiological studies support an association between dietary fat, particularly saturated or animal fats, and prostate cancer risk. Of these, several suggest reduced risk with low-fat diets high in n-3 fatty acids and increased risk with high-fat diets rich in n-6 fatty acids. Others suggested association with higher meat intake, possibly due to heterocyclic amines and polycyclic aromatic hydrocarbons, produced during grilling or frying. Positive association of prostate cancer risk with dairy intake could involve alpha-methylacyl-CoA racemase activity (required for beta-oxidation of phytanic acid present in dairy products and red meat) or the suppression of vitamin D activity by calcium. Inverse associations were observed with dietary intake of plant foods. These include cereals, soy products, and fruit and vegetable sources of carotenoids. Numerous plant constituents may act synergistically in the prevention and inhibition of prostate disorders. These diet-risk associations may lead to future individualized diet recommendations based upon genetic polymorphisms.     

In vitro batch fecal fermentation comparison of gas and short-chain fatty acid production using "slowly fermentable" dietary fibers

Abstract: Sustained colonic fermentation supplies beneficial fermentative by‐products to the distal colon, which is particularly prone to intestinal ailments. Blunted/delayed initial fermentation may also lead to less bloating. Previously, we reported that starch‐entrapped alginate‐based microspheres act as a slowly fermenting dietary fiber. This material was used in the present study to provide a benchmark to compare to other “slowly fermentable” fibers. Dietary fibers with previous reports of slow fermentation, namely, long‐chain inulin, psyllium, alkali‐soluble corn bran arabinoxylan, and long‐chain β‐glucan, as well as starch‐entrapped microspheres were subjected to in vitro upper gastrointestinal digestion and human fecal fermentation and measured over 48 h for pH, gas, and short‐chain fatty acids (SCFA). The resistant fraction of cooked and cooled potato starch was used as another form of fermentable starch and fructooligosaccharides (FOS) served as a fast fermenting control. Corn bran arabinoxylan and long‐chain β‐glucan initially appeared slower fermenting with comparatively low gas and SCFA production, but later fermented rapidly with little remaining in the final half of the fermentation period. Long‐chain inulin and psyllium had slow and moderate, but incomplete, fermentation. The resistant fraction of cooked and cooled potato starch fermented rapidly and appeared similar to FOS. In conclusion, compared to the benchmark slowly fermentable starch‐entrapped microspheres, a number of the purported slowly fermentable fibers fermented fairly rapidly overall and, of this group, only the starch‐entrapped microspheres appreciably fermented in the second half of the fermentation period. Practical Application: Consumption of dietary fibers, particularly commercial prebiotics, leads to uncomfortable feelings of bloating and flatulence due to their rapid degradation in our large intestine. This article employs claimed potential slowly fermenting fibers and compares their fermentation rates with a benchmark slow fermenting fiber that we fabricated in an in vitro simulation of the human digestive system. Results show a variety of fermentation profiles only some of which have slow and extended rate of fermentation.     

菊粉和大豆膳食纤维对牛肉饮食的小鼠肠道菌群及其代谢产物的改善作用

红肉的大量摄入会导致其未消化成分经肠道菌群发酵形成有害代谢产物,从而破坏肠稳态,增加患结肠癌、心血管疾病的风险.为探究添加菊粉和大豆膳食纤维对牛肉饮食小鼠的肠道菌群及代谢产物的影响,本实验将雄性C57BL/6Cnc小鼠随机分为空白对照组、牛肉组、牛肉与菊粉组和牛肉与大豆膳食纤维组,通过16S rRNA高通量测序技术检测...     

江蓠藻膳食纤维降血脂作用研究

采用高脂饲料喂养昆明小鼠建立高脂血症模型,以燕麦膳食纤维为阳性对照,测定江蓠藻膳食纤维100、200、400mg/(kg bw·d)剂量灌胃给药高脂血症模型小鼠,4 周后对其总胆固醇(TC)、甘油三酯(TG)、低密度脂蛋白胆固醇(LDL-C)、高密度脂蛋白胆固醇(HDL-C)的影响。结果表明：江蓠藻膳食纤维能显著降低高血脂模型小鼠血清中TC、TG、LDL-C 的含量,降低肝脏脂质水平,同时升高血清HDL-C 含量。江蓠藻膳食纤维具有调节脂质代谢的作用,可降低高脂膳食导致的氧化损伤。     

谷物膳食纤维与结肠健康

膳食纤维(DF)为微生物生长提供均衡的能量和营养,这是维持结肠生态系统平衡所必需的。另外,膳食纤维的发酵,特别是丁酸发酵,有利于结肠健康。目前,结肠癌、炎症性肠炎和其他结肠紊乱疾病已经严重影响身体健康。作者综述了谷物膳食纤维中非淀粉谷物多聚糖、抗性淀粉,通过发酵产物短链脂肪酸和菌群的调节对于结肠健康的影响。     

Pharmacological Intervention through Dietary Nutraceuticals in Gastrointestinal Neoplasia

Neoplastic conditions associated with gastrointestinal (GI) tract are common worldwide with colorectal cancer alone accounting for the third leading rate of cancer incidence. Other GI malignancies such as esophageal carcinoma have shown an increasing trend in the last few years. The poor survival statistics of these fatal cancer diseases highlight the need for multiple alternative treatment options along with effective prophylactic strategies. Worldwide geographical variation in cancer incidence indicates a correlation between dietary habits and cancer risk. Epidemiological studies have suggested that populations with high intake of certain dietary agents in their regular meals have lower cancer rates. Thus, an impressive embodiment of evidence supports the concept that dietary factors are key modulators of cancer including those of GI origin. Preclinical studies on animal models of carcinogenesis have reflected the pharmacological significance of certain dietary agents called as nutraceuticals in the chemoprevention of GI neoplasia. These include stilbenes (from red grapes and red wine), isoflavones (from soy), carotenoids (from tomatoes), curcuminoids (from spice turmeric), catechins (from green tea), and various other small plant metabolites (from fruits, vegetables, and cereals). Pleiotropic action mechanisms have been reported for these diet-derived chemopreventive agents to retard, block, or reverse carcinogenesis. This review presents a prophylactic approach to primary prevention of GI cancers by highlighting the translational potential of plant-derived nutraceuticals from epidemiological, laboratory, and clinical studies, for the better management of these cancers through consumption of nutraceutical rich diets and their intervention in cancer therapeutics.     

Influence of Hydrocolloids (Dietary Fibers) on Lipid Digestion of Protein‐Stabilized Emulsions: Comparison of Neutral,Anionic, and Cationic Polysaccharides

The impact of dietary fibers on lipid digestion within the gastrointestinal tract depends on their molecular and physicochemical properties. In this study, the influence of the electrical characteristics of dietary fibers on their ability to interfere with the digestion of protein‐coated lipid droplets was investigated using an in vitro small intestine model. Three dietary fibers were examined: cationic chitosan; anionic alginate; neutral locust bean gum (LBG). The particle size, ζ‐potential, microstructure, and apparent viscosity of β‐lactoglobulin stabilized oil‐in‐water emulsions containing different types and levels of dietary fiber were measured before and after lipid digestion. The rate and extent of lipid digestion depended on polysaccharide type and concentration. At relatively low dietary fiber levels (0.1 to 0.2 wt%), the initial lipid digestion rate was only reduced by chitosan, but the final extent of lipid digestion was unaffected by all 3 dietary fibers. At relatively high dietary fiber levels (0.4 wt%), alginate and chitosan significantly inhibited lipid hydrolysis, whereas LBG did not. The impact of chitosan on lipid digestion was attributed to its ability to promote fat droplet aggregation through bridging flocculation, thereby retarding access of the lipase to the droplet surfaces. The influence of alginate was mainly ascribed to its ability to sequester calcium ions and promote depletion flocculation.     

Enhancement of colon and stomach carcinogenesis in 1,2-dimethylhydrazine-treated rats fed a diet high in heterocyclic amines

 Epidemiological studies have linked the consumption of red meat and the consumption of highly browned meats containing high levels of heterocyclic aromatic amines (HCAs) to increased risk of colorectal cancer or polyps. We have examined the effects of long-term feeding of beef-containing diets with low and high levels of HCAs (in the context of a low- or high-beef tallow diet) on a standard 1,2-dimethylhydrazine (DMH)-induced colon tumorigenesis protocol. Feeding of a beef diet high in HCAs resulted in more DMH-induced colon adenocarcinomas, but only in the context of a low fat diet. The high HCA diets increased stomach tumors in all DMH-treated rats. An apparent interaction of high HCA levels with a high fat level reduced the colon tumor incidence and tumor numbers in those rats on diets containing both these factors. These results support the epidemiological data linking well-cooked meat to increased risk for colon and stomach cancer, but the role of the dietary fat level remains puzzling. Additionally, we examined the DNA of liver, colon, and stomach from control rats (not treated with DMH) fed a high level of HCAs for 27 weeks. The genomic DNA was analyzed for the presence of 2-amino-1-methyl-6-phenylimidazo[4,5-f]pyridine (PhIP) adducts by ³²P-postlabeling analysis and was also used in PCR to amplify the rat p53 and Apc genes, followed by direct dye-terminator DNA sequencing. Results showed that no PhIP adducts were present in any tissue. In addition, there were no signature p53 or Apc gene mutations seen in the colon or stomach DNA. These results indicate that the high level of HCAs present in a diet of well-cooked meat does not cause (1) persistent PhIP adducts similar to those produced by feeding pure PhIP at high doses or (2) p53 and Apc gene mutations in nontumor tissue. Received: 23 April 1998     

Effects of dietary fiber and phytic acid on mineral availability.

In general, it has been shown that dietary fiber may bind metallic cations in both in vitro and in vivo studies. However, there clearly are many unresolved questions on the effects of high-fiber diets on mineral availability. On one side, the effects of fiber on the utilization of nutrients vary greatly with the amount and type of fiber. In addition, there are many agents in both food and the digestive tract that may affect the mineral binding to fiber: some agents may inhibit binding, while others will enhance it. Also, there are several major difficulties in drawing conclusions from the in vitro and in vivo studies due to the different experimental conditions, methods used to follow the mineral balance, etc. Finally, it must be borne in mind that fiber and phytic acid occur together in fiber-rich diets and, thus, it is difficult to separate the effects of fiber and phytate in the utilization of most essential polyvalent metallic ions. The studies summarized in this review show that the recommendation for increasing dietary fiber in Western communities would not be expected to have any adverse effect on mineral absorption if we increase not only the intake of fiber, but also the dietary intake of other food components such as protein (both vegetable and animal protein) and ascorbic, citric, and oxalic acids (in fruits and vegetables). The adequate intake of minerals, fat, and simple sugars are maintained with this type of diet. The recommendations should be best interpreted in such a way as to prevent the consumption of excessive amounts of phytate, particularly for those whose mineral needs are great. Further studies are still needed in this field in order to understand the conflicting results published in the literature regarding the effects of fiber on the utilization of minerals; however, the studies reviewed in this article may give us an idea of the complexity of mineral availability in fiber-rich, phytate-rich diets.     

Cowpea: an overview on its nutritional facts and health benefits

Cowpea (Vigna unguiculata) is a legume consumed as a high‐quality plant protein source in many parts of the world. High protein and carbohydrate contents with a relatively low fat content and a complementary amino acid pattern to that of cereal grains make cowpea an important nutritional food in the human diet. Cowpea has gained more attention recently from consumers and researchers worldwide as a result of its exerted health beneficial properties, including anti‐diabetic, anti‐cancer, anti‐hyperlipidemic, anti‐inflammatory and anti‐hypertensive properties. Among the mechanisms that have been proposed in the prevention of chronic diseases, the most proven are attributed to the presence of compounds such as soluble and insoluble dietary fiber, phytochemicals, and proteins and peptides in cowpea. However, studies on the anti‐cancer and anti‐inflammatory properties of cowpea have produced conflicting results. Some studies support a protective effect of cowpea on the progression of cancer and inflammation, whereas others did not reveal any. Because there are only a few studies addressing health‐related effects of cowpea consumption, further studies in this area are suggested. In addition, despite the reported favorable effects of cowpea on diabetes, hyperlipidemia and hypertension, a long‐term epidemiological study investigating the association between cowpea consumption and diabetes, cardiovascular disease and cancer is also recommended. © 2018 Society of Chemical Industry