体外消化模型在真菌毒素生物可及性研究中的应用及研究进展

在人类健康风险评估中,经口摄入是人类暴露于许多污染物的主要途径.模拟污染物经口腔、胃和小肠消化过程的体外消化模型已成为探究污染物生物可及性、肠转运和代谢的热点,并成为评估食品、土壤等基质中重金属、有机污染物、真菌毒素风险的重要技术手段.模拟机体进食、禁食条件创建体外消化模型并验证,探讨真菌毒素在体内的生物可及性及影响因素,对发展准确、灵敏、方便的膳食暴露真菌毒素风险评估工具意义非凡.本文就真菌毒素生物可及性研究的最新进展进行综述.     

胃食管反流病的临床诊治

胃食管反流病(简称GERD)是指胃、十二指肠内容物反流入食管引起的以烧心、反酸为主要特征的临床综合征.一般来说,胃内贮存着胃酸,十二指肠腔内有胆汁液,这些都是消化液,可消化进食的肉类或其他食物.胃内天生有层像瓷器层样的粘膜屏障保护,因此胃酸呆在胃内很安全.当进食时,大量胃酸分泌消化胃腔内的食物,将胃酸中和后排入十二指肠再进一步被该处胆汁的作用继续消化直到经小肠吸收后残渣变成粪便排出.若胃液反流入食管腔,食管无瓷器样的粘膜保护层,胃酸就会腐蚀破坏食管粘膜引起糜烂、溃疡.     

胆汁反流性胃炎中医防治

胆汁反流性胃炎在慢性胃炎中占一定比例，近年来有增多趋势。其主要原因是由于胃与十二指肠连接处幽门括约肌张力下降，致幽门关闭失调所致。人在进食时，食物由口腔进入食道，再由食道下口贲门进入胃内，通过胃的蠕动，初步消化食物，然后由幽门进入十二指肠。正常情况下，十二指肠内胆汁不会反流入胃，如果幽门关闭不全就会造成胆汁反流性胃炎。[第一段]     

体外模拟消化实验研究虾蛄和梭子蟹体内铅镉元素的生物可给性

目的 探讨虾蛄和梭子蟹体内重金属元素铅(Pb)和镉(Cd)的生物可给性，为研究动物性水产品的食用风险提供实验方法。方法 采用体外模拟消化实验，模拟人体胃肠道的物理化学环境，对虾蛄和梭子蟹样品进行仿生消解，以电感耦合等离子体质谱法(ICP-MS)分别测定样品、模拟胃和肠消化提取液中Pb和Cd的含量，开展生物可给性计算，分析样品中目标重金属在人体胃肠道中的可能溶解情况，以国标限量对结果进行初步评估。结果 3批虾蛄和梭子蟹样品中Cd含量在1.18～2.23 mg/kg, Pb含量在0.018 6～0.066 8 mg/kg。样品经模拟消化液消化分解后，生物可给性以虾蛄胃消化液Cd(89.2%～93.5%)最高，虾蛄肠消化液Pb(17.3%～20.7%)最低。结论 虾蛄和梭子蟹中Pb、Cd不能被人体全部吸收，模拟胃消化液的生物可给性高于模拟肠消化液。     

胃食管反流病的临床诊治

胃食管反流病(简称GERD)是指胃、十二指肠内容物反流入食管引起的以烧心、反酸为主要特征的临床综合征。一般来说,胃内贮存着胃酸,十二指肠腔内有胆汁液,这些都是消化液,可消化进食的肉类或其他食物。胃内天生有层像瓷器层样的粘膜屏障保护,因此胃酸呆     

粪便检查

人吃进去的食物经口腔、咽喉、食道入胃被消化;再由胃进入十二指肠,遇胰液、胆汁、小肠液继续充分消化;当食物运送到回肠时已变为流动食糜,到大肠时营养成分基本被吸收,而且把绝大部分的水分重吸收。剩余的仅是食物残渣、     

饮食与消化性溃疡

消化性溃疡是消化系统的常见病,本病可发生于胃,十二指肠等与胃酸直接接触的任何部位。这种病除了与遗传等因素有关外,饮食不当是不容忽视的“损害因素”。 进食过快、食物过于粗糙会造成食道、胃粘膜机械性磨损乃至出血;暴饮暴食能引起胃过度扩张,胃窦受刺激分泌过多的胃泌素继而产生大量胃酸而损伤胃;吃饭不定时或常吃零食会打破正常的胃液分泌和胃活动节律;过热的饮食能引起食道和胃粘膜直接烫伤;过冷食品可使胃血管收缩,降低血流量,从而削弱胃的消化能力和防御能力,并通过神经反射引起胃运动障碍;一些刺激性食物可直接损害胃粘膜屏障或促使胃酸产生过多而伤及胃。     

老人进食,慢品细嚼益处多

人到老年,随着机体衰老,脏器形态、结构、功能会发生退行性变化,消化道黏膜萎缩、黏液分泌减少,消化功能和运动功能减弱。一般情况下食物经口腔咀嚼后由食管经胃到十二指肠、小肠、结肠排出体外。食管和气管开口相邻,外界食物由口腔吞咽进入食管时,喉上部有一块组织叫会厌软骨(一片薄膜样组织),可覆盖住气管开口,防止异物进入。     

儿童消化系统发育生理研究进展

儿童营养需求与成人不同,而其消化系统功能却还不成熟。本文对儿童消化系统中口腔、胃肠运动、消化酶发育生理特点进行总结,其特点包括胃内pH高、胃肠酶分泌量和活性低、胃排空和肠蠕动慢、肠屏障功能低下,为儿童保健、营养供应、儿童食品的开发及体外消化模型提供参考,并提出了未来的研究方向。     

医患连线

上海卢湾区的成大爷问:我患胆囊炎和胆石症,请问在饮食上应注意什么?连线医生——太钢迎新医院普外科主任卞力军答:(1)胆囊炎在急性发作期,忌食油炸、煎的食物,忌食蛋类、肉汤及饮酒;进食应限于低脂肪、低蛋白、少量易消化的流食或半流食。(2)慢性胆囊炎患者,平日进食应以清淡、易消化的食物为主,应进大量饮料(15002000ml),以稀释胆汁。每2～3小时进食1次。(3)宜定时定量,少吃多餐,不宜过饱。在饮食结构上,严格控制脂肪和含胆固醇食物,如肥肉、油炸食品、动物内脏等,不可饮酒和进食辛辣食物,宜多吃萝卜、青菜、豆类、豆浆等副食。萝卜有利胆作用,并能帮助脂肪的消化吸收;青菜含大量维生素、纤维素;豆类含丰富的植物蛋白。此外,还应补充一些水果、果汁等,以弥补炎症造成的津液和维生素的损失。(4)一般宜进低脂肪、低胆固醇饮食。肥肉,油炸食品,含油脂多的干果、果仁类食物及蛋黄,动物脑、肝、肾及鱼子等食品均宜严格控制。平时饮食亦应进易消化、少渣滓食物以避免产生气体。急性发作时宜予低脂、易消化半流食或流食;重者应予禁食、胃肠减压及静脉补液。     

Development of an in vitro digestion model for estimating the bioaccessibility of soil contaminants

Soil ingestion can be a major route of human exposure to many immobile soil contaminants. The present risk assessment is based on toxicity studies in which contaminants are typically ingested in liquid or food matrices. The difference in bioavailability of contaminants ingested in a soil matrix is not taken into account. To become bioavailable, contaminants first need to become bioaccessible, i.e., they must be mobilized from the soil during digestion. Soil contaminants may be less bioaccessible than contaminants from liquid or food, so that the risks can be overestimated. This article describes the development of an in vitro human digestion model that is physiologically based. It can be used as a tool to assess bioaccessibility. We explain the rationale behind the experimental design of the model. We address the aspects of the simulated compartments of the gastrointestinal tract, temperature, soil-to-fluid ratio, ratio of digestive juices, transit times, centrifugation, pH values, mixing, constituents and their concentrations, and bile. The optimized in vitro digestion model was applied in a case study. The bioaccessibility of lead in pottery flakes with glazing was determined and compared to the bioaccessibility of lead in the soil from which the pottery flakes were removed. The data indicate that pottery flake lead is considerably less bioaccessible (0.3 +/- 0.2%) than lead in soil without pottery flakes (42-66% at the same site, and 28-73% at other sites in the same town). Furthermore, bioaccessibility values of lead in soil appear to be less than calculated bioaccessibility values for dietary lead (which are based on the criterion used by the Dutch risk assessment and on literature absorption data). This indicates that accounting for the matrix of ingestion can affect the exposure assessment for lead. The in vitro digestion model is a promising tool for studying the effect of the ingestion matrix on bioaccessibility.     

Development of an <Emphasis Type="Italic">In Vitro</Emphasis> Digestion Model for Estimating the Bioaccessibility of Soil Contaminants

Soil ingestion can be a major route of human exposure to many immobile soil contaminants. The present risk assessment is based on toxicity studies in which contaminants are typically ingested in liquid or food matrices. The difference in bioavailability of contaminants ingested in a soil matrix is not taken into account. To become bioavailable, contaminants first need to become bioaccessible, i.e., they must be mobilized from the soil during digestion. Soil contaminants may be less bioaccessible than contaminants from liquid or food, so that the risks can be overestimated. This article describes the development of an in vitro human digestion model that is physiologically based. It can be used as a tool to assess bioaccessibility. We explain the rationale behind the experimental design of the model. We address the aspects of the simulated compartments of the gastrointestinal tract, temperature, soil-to-fluid ratio, ratio of digestive juices, transit times, centrifugation, pH values, mixing, constituents and their concentrations, and bile. The optimized in vitro digestion model was applied in a case study. The bioaccessibility of lead in pottery flakes with glazing was determined and compared to the bioaccessibility of lead in the soil from which the pottery flakes were removed. The data indicate that pottery flake lead is considerably less bioaccessible (0.3 ± 0.2%) than lead in soil without pottery flakes (42–66% at the same site, and 28–73% at other sites in the same town). Furthermore, bioaccessibility values of lead in soil appear to be less than calculated bioaccessibility values for dietary lead (which are based on the criterion used by the Dutch risk assessment and on literature absorption data). This indicates that accounting for the matrix of ingestion can affect the exposure assessment for lead. The in vitro digestion model is a promising tool for studying the effect of the ingestion matrix on bioaccessibility. Received: 23 December 2001/Accepted: 24 July 2002     

Micellarization and intestinal cell uptake of beta-carotene and lutein from drumstick (Moringa oleifera) leaves

The leaves and pods of the drumstick tree are used as food and medicine in some Asian and African countries. Although relatively high concentrations of beta-carotene and lutein have been reported in the leaves, the bioavailability of these carotenoids from this source is unknown. We have analyzed the digestive stability and bioaccessibility of carotenoids in fresh and lyophilized drumstick leaves using the coupled in vitro digestion/Caco-2 cell model. Beta-carotene and lutein were stable during simulated gastric and small intestinal digestion. The efficiency of micellarization of lutein during the small intestinal phase of digestion exceeded that of beta-carotene. Addition of peanut oil (5% vol/wt) to the test food increased micellarization of both carotenoids, and particularly beta-carotene. Caco-2 cells accumulated beta-carotene and lutein from micelles generated during digestion of drumstick leaves in a time- and concentration-dependent manner. The relatively high bioaccessibility of beta-carotene and lutein from drumstick leaves ingested with oil supports the potential use of this plant food for improving vitamin A nutrition and perhaps delaying the onset of some degenerative diseases such as cataracts.     

Effects of pectins and sugars on β-carotene bioaccessibility in an in vitro simulated digestion model

There is lack of information about the effects of pectin and sugars on carotenoid delivery in a simple juice model system. Therefore, the effect of pectin and sugars on β-carotene bioaccessibility (CBA) and the characteristics of digestive fluids in juice model systems were studied. Carotenoid retention ratio (CRR) in the small intestine and the characteristics of digestive fluids, including color parameters and rheological properties, were investigated to gain insight into the mechanism that can alter carotenoid bioaccessibility. Results illustrated that higher pectin concentration, medium methoxyl pectin (MMP), and low methoxyl pectin (LMP) increased the initial apparent viscosity. However, there was no marked difference for the apparent viscosity of all systems in the stomach and small intestine phases. Generally, systems with sugars had higher CRR than those with pectin. Lower pectin concentration increased CBA. Systems with MMP had higher CBA than those containing high methoxyl pectin (HMP) and LMP; therefore, the effects of degree of methoxylation (DM) were not proportional to CBA. Among systems with different sugars, sucrose could achieve the highest CBA (4.59%). A comprehensive investigation of the effects of pectin and sugars on carotenoid delivery during digestion will be a theoretical guidance to improve nutritional qualities of juice products.     

Comparison of different digestive tract models for estimating bioaccessibility of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) from red slag 'Kieselrot'

'Kieselrot' (red slag), a highly PCDD/F-contaminated leaching residue from a copper production process, has been used as surface layer for more than 1,000 sports fields, playgrounds and pavements in Germany and neighbouring countries. Children can ingest this material directly by hand-to-mouth activities or soil-pica behaviour. Furthermore secondary contamination of farm land or kitchen gardens by drift of red slag dust may lead to an enrichment of PCDD/F within the food-chain. PCDD/F can be mobilized from contaminated materials by digestive juices and thus become bioaccessible for intestinal absorption. Two different digestive tract models were used to estimate the bioaccessibility of PCDD/F from red slag and to study the influence of food material on the mobilization of the contaminants. The bioaccessibility of PCDD/F from red slag depends on the charge of red slag material used, the bile content of the intestinal juice and on the presence of lipophilic foodstuffs. A low bioaccessibility of less than 5% was found when using a digestive tract model with a low bile content and in absence of food material. The bioaccessibility was estimated to be more than 60% when using a model with a higher bile content and in the presence of whole milk powder. A low bioaccessibility of PCDD/F from red slag in general--as assumed until now and mentioned in legal provision--was not confirmed by our study. Considering observations for the different homologue groups it is obvious that bioaccessibility is the first of several important steps to estimate human health risks arising from contaminated materials. In case red slag contaminated with PCDD/F their absorption rate in the digestive tract and/or metabolism might be at least just like important.     

Effects of pH on mineral-phytate,protein-mineral-phytate,and mineral-fiber interactions. Possible consequences of atrophic gastritis on mineral bioavailability from high-fiber foods.

A common gastrointestinal tract problem afflicting the elderly is that of reduced hydrochloric acid secretion by the stomach mucosa. This results in raised stomach pH values and in reduced activity of the digestive enzyme pepsin, which is responsible for the hydrolysis of dietary proteins to polypeptides. The effects of these alterations of the stomach on the digestion of high-fiber foods and resultant mineral bioavailability have not been defined. This paper reviews the effects of pH on the mineral-phytate, protein-mineral-phytate, and mineral-fiber interactions that would be present in high-fiber foods. Possible consequences of raised stomach pH values on mineral bioavailability from high-fiber foods are discussed.     

Bioavailability of carotenoids and alpha-tocopherol from fruit juices in the presence of absorption modifiers: in vitro and in vivo assessment

The food industry is playing an increasing role in the development and marketing of new products although little is known regarding the bioavailability of the phytochemicals they contain. Our aim was to assess the effect of the presence of absorption modifiers (milk and iron) on the in vitro bioaccessibility and the serum response in vivo of carotenoids and alpha-tocopherol from fruit juices. Thirty-two young women participated in a three-period (21 d each) supplementation study with a 2-week wash-out in between. Subjects consumed consecutively 2 x 250 ml/d vitamin C-fortified juices supplied as fruit juice, fruit juice containing milk and fruit juice containing milk and iron. Fasting blood samples were collected before and after each supplementation period. In vitro bioaccessibility of carotenoids and alpha-tocopherol was assessed by a static digestion model. Vitamin E and carotenoids from both studies were determined by HPLC. In vitro, xanthophyll ester hydrolysis and transference of free xanthophylls and alpha-tocopherol into the micellar phase were higher in the presence of absorption modifiers. In vivo, consumption of the fruit juices provoked significant increments (within-subject) of alpha-tocopherol and some carotenoids in serum. Dose-adjusted increments in serum of some carotenoids were higher when subjects consumed juices with milk and milk plus iron, although differences did not reach statistical significance. In conclusion, the presence of milk and milk plus iron do not influence the bioavailability of carotenoids and alpha-tocopherol from fruit juices in vivo. Our results support the use of in vitro models to assess food-related factors affecting bioavailability of carotenoids and tocopherols from foods.     

Effects of pH on mineral-phytate, protein-mineral-phytate, and mineral-fiber interactions. Possible consequences of atrophic gastritis on mineral bioavailability from high-fiber foods

A common gastrointestinal tract problem afflicting the elderly is that of reduced hydrochloric acid secretion by the stomach mucosa. This results in raised stomach pH values and in reduced activity of the digestive enzyme pepsin, which is responsible for the hydrolysis of dietary proteins to polypeptides. The effects of these alterations of the stomach on the digestion of high-fiber foods and resultant mineral bioavailability have not been defined. This paper reviews the effects of pH on the mineral-phytate, protein-mineral-phytate, and mineral-fiber interactions that would be present in high-fiber foods. Possible consequences of raised stomach pH values on mineral bioavailability from high-fiber foods are discussed.     

Content and bioaccessibility of carotenoids from organic and non-organic baby foods

Although organic baby foods are assumed to be more nutritious than their conventional counterparts, research data in this area are limited and equivocal. The objectives of the present study were first, to determine the carotenoid content of organic and non-organic baby foods; and, second, to analyze the bioaccessibility of carotenoids from these products. The baby foods selected for analysis were for the same age group (4+ months) and of two types: chicken and vegetable dinners and berry-based desserts. All foods were subjected to an in vitro digestion procedure which simulates gastrointestinal digestion. Due to their ingredient composition, carotenoid content and bioaccessibility varied within and between the organic and non-organic foods. In general, the non-organic berry-based desserts contained more carotenoids than the organic type. Although the carotenoids had a greater % bioaccessibility from the desserts than the dinners, the chicken and vegetable meals provided significantly higher amounts of carotenoids. Our findings show that carotenoid content reflects the ingredient composition of the baby meals. Therefore, the organic dinners tested were generally not superior to the non-organic foods in terms of carotenoid content and bioaccessibility.     

Use of the refractometer as a tool to monitor dietary formula concentration in gastric juice

BACKGROUND AND AIMS: Critically ill patients do not always tolerate nasogastric tube feeding. Gastric residual volumes are widely used to evaluate feeding tolerance, but controversy exists about what constitutes the residual volume (diet formula or digestive juice). In this paper, we describe the use of the refractometer as a tool to monitor dietary formula concentration in gastric juice and evaluate gastric juice refractometry as a possible clinical application. METHODS: Brix value (an index of the total solutes in solution) readings for polymeric diet at pH 1, 4, 7 and 8, and at 4 degrees C, 25 degrees C and 37 degrees C, and in fasting gastric juice were determined with a refractometer. RESULTS: We found that distilled water, minerals, and vitamins had low Brix values of 0+/-0, 1.2+/-0.1, and 0.4+/-0.1, respectively. On the other hand, because carbohydrate (17 g/100 ml), protein (5.3 g/100 ml), fat (4.1 g/100 ml), and full-strength polymeric diet had high concentrations of dissolved nutrients, they also had high Brix values (12.1+/-0.6, 6.5+/-0.1, 6.0+/-0.1, and 23.5+/-0.1, respectively). The Brix values of polymeric diet had a linear additive relationship with the diet formula concentration at various pHs, temperatures, and in the gastric juice. CONCLUSION: Brix value measurement can be used to monitor stomach dietary formula concentration. Such information can be obtained at the bedside and used to evaluate feeding-intolerant patients receiving enteral feeding.