第一章植物学基础2-营养与食品卫生.ppt

单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,Main contents,Definition of carbohydrates,Classification of carbohydrates,Digestion&absorption of CHO,Functions of carbohydrates,Disorders related to CHO metabolism,Dietary reference intakes of CHOs,Carbohydrates,are,one,of the three,macronutrient,types that,provide energy,to our bodies.Carbohydrates,contain,carbon,hydrogen,and oxygen.,碳水化合物：属三大能量营养素之一，主要由碳、氢、氧构成。,一,、碳水化合物的定义,What are carbohydrates?,Carbohydrate can be abbreviated as,“,CHO,”,.,We obtained carbohydrates predominantly from plant foods such as,fruits,vegetables,and,grain,.,Why?,HO,H,CH2,OH,H,OH,OH,HO,H,H,H,Glucose,OH,OH,HO,H,HO,H,CH,2,OH,CH,2,OH,Fructose,HO,OH,OH,OH,H,H,H,H,CH,2,OH,Galactose,The,three most common monosaccharides.ALL of them contain,identical,atoms,Structure of monosaccharides,Monosaccharides-Glucose（葡萄糖）,Glucose is the,most abundant,sugar molecule found in our diets and in our foods.,Glucose does,not generally occur,by itself in foods but attaches to other sugars to form disaccharides and complex carbohydrates.,In our bodies,glucose is the,preferred,source of energy,for the brain.,食物中最多的单糖，但不以单独形式存在，常与其他糖形成双糖或多糖的形式存在，葡萄糖优先为大脑提供能量。,Monosaccharides-,Fru,ctose（果糖）,Fructose is also called,fruit sugar,.,Fructose is the,sweetest,natural sugar,occurs naturally in fruits and vegetables.,Prefix,Monosaccharides-Galactose（半乳糖）,Galactose,does,not occur alone,in foods.It joins with,glucose,to create lactose,one of the disaccharides.,Sweetest monosaccharides?,The most abundant monosaccharides?,The sweetest：fructose,The most abundant：glucose,Di,saccharide,（双糖）,Di,saccharide,:A carbohydrate compound consisting of,two sugar molecules,joined together.,The,three,most common disaccharides found in foods,are,lactose,（乳糖）,maltose,（麦芽糖）,and,sucrose,（蔗糖）,.,Disaccharides,Lactose,（乳糖）,Glucose,Galactose,Lactose,Lactose:,Consist of one glucose molecule and one,galactose,(,半乳糖）,molecule.,Di,saccharidesMaltose,（麦芽糖）,Maltose:also called,malt sugar,consist of two molecules of,glucose,.,It does not,generally occur by itself in foods,but results as a by-product of digestion.,Glucose,Di,saccharidesSucrose,（蔗糖）,Sucrose,is composed of one,glucose,molecule and one,fructose,（果糖）,molecule.,Sucrose provides much of the sweet taste found in honey,fruits,and vegetables.,How about the Sucrose and fructose?,Sweeter,than lactose or maltose,why?,哪种双糖最甜-麦芽糖，蔗糖，乳糖？,麦芽糖-2个葡萄糖,蔗糖-1个葡萄糖+1个果糖,乳糖-1个葡萄糖+1个半乳糖,蔗糖,Oligosaccharide,（寡糖）,Oligosaccharide are composed of 3 to 10,monosaccharides,.,The most common oligosaccharides are,raffinose,（棉籽糖）,and,stachyose,（水苏糖）,.,They can not be degraded by enzymes in the small intestine,but can be broke down in the large intestine.,Polysaccharides,（多糖）,Polysaccharides,include,starch（淀粉）,glycogen（糖原）,and,most fibers（纤维）.,Polysaccharides,Starch,Glycogen,Fiber,淀粉,糖原,纤维,Polysaccharide-Starch,Starch:A polysaccharide stored in plants and is the,storage form,of glucose in plants.,（淀粉是葡萄糖在植物中的贮存形式）,Excellent food sources of starch include?,grains(wheat,rice,corn,oats,and barley),legumes(peas,beans,and lentils),and tubers(potatoes and yams).,Our bodies easily digest most starches,，,we call them,digestible starch,(,可吸收淀粉）,.,根据其结构可分为直链淀粉,（,amylose,）,和支链淀粉,（,amylopectin,），,前者易使食物老化，后者易使食物糊化,（,gelatinization,）,。,However,some starch in plants is not digestible and is called,resistant starch,（抗性淀粉）,.,抗性淀粉：指健康者小肠中不吸收的淀粉及其降解产物。,When our intestinal bacteria try to digest,resistant starch,a fatty acid called,butyrate,is produced.,Consuming resistant starch may be beneficial because,butyrate,is suggested to reduce the risk of cancer.,豆科食物,（,Legumes含有的抗性淀粉比谷类,、,蔬菜和水果多。,Bean sprout,Green soybean,Glycogen:A polysaccharide,stored,in animals,including humans.,Very little glycogen exists in food.,Thus,glycogen is,not a dietary source,of carbohydrate.,Polysaccharide-Glycogen,（糖原）,Which tissues are abundant in glycogen?,We store glycogen in our,muscles,and,liver,.We can break down glycogen very quickly into glucose when we need it for energy.,Based on the water soluble ability,fiber can be classified into,soluble fibers,and,insoluble fibers.,Insoluble fibers,（不溶性纤维）,:cellulose,（纤维素）,hemicellulose,（半纤维素）,and,xylogen,（木质素）,.,Soluble fibers,（可溶性纤维）,:,果胶,（,pectin),，,树胶和粘胶,.,Polysaccharide-Fiber,膳食纤维,（,dietary fiber,）,：是指植物性食物或原料中糖苷键大于,3,个，不能被人体小肠消化和吸收，但对人体健康有意义的碳水化合物。,膳食纤维包括部分非淀粉多糖（纤维素、半纤维素、木质素、果胶等）、,抗性淀粉,、,葡聚糖,以及,部分低聚糖,等。,(1),增强肠道功能、有利粪便排出,Helps prevent consti,p,ation and other intestinal problems by keeping our stools moist and soft.,Functions of dietary fiber,Dietary fiber increases faecal bulk through water binding by fiber.,Fiber gives gut muscles“something to push”and makes it easier to eliminate stools.,(2),控制体重和减肥,May enhance,weight loss,as eating a high fiber diet causes a person to feel more full.,Fiber,absorbs water,expands,in our,intestine,and,slows,the movement of food through the upper part of the digestive tract.,(3),降低血糖和血胆固醇,Decrease the level of blood sugar and cholesterol,May reduce the risk of heart disease by delaying or blocking the absorption of dietary cholesterol into the bloodstream.,(4),降低结肠癌的发病风险,May reduce the risk of colon cancer.,While there is still some,controversy,surrounding this issue,many researchers believe that fiber binds,cancer-causing substances,and speeds their elimination from the colon.,三、碳水化合物的消化及吸收,We have learned many forms of,CHOs,containing in our foods,which one is the form of energy used by our bodies?,The primary goal of CHO digestion is to break down polysaccharides and disaccharides into,monosaccharides,that can be converted to,glucose.,Digestion of carbohydrates in foods(In the mouth),CHO digestion begins in the mouth.,Question:,When you eat,steamed bread（馒头）,notice that you can actually taste it becoming sweeter,Why?,Sa,l,iva,amylase,（淀粉酶）,breaks,starch,(,淀粉）,into smaller particles and eventually into the,maltose,（麦芽糖）,.,Disaccharides are not digested in the mouth.,In the stomach,all digestion of,CHOs,ceases.,Digestion of carbohydrates in foods(In the stomach),Because the acid in the stomach inactivates most of the sa,l,ivary amylase enzyme.,Would you guess the reasons?,The,majority,of carbohydrate digestion occurs in the,small intestine,.,Digestion of carbohydrates in foods(In the small intestine),Pancreatic amylase secreted by the pancreas into the small intestine.,Pancreatic amylase continues to digest any remaining starch into,maltose,（麦芽糖）,.,Additional enzymes found in the intestinal,tract,break down disaccharides,into,monosaccharides.,Maltose,Sucrose,Lactose,Glucose,Glucose&Fructose,Glucose&Galactose,Maltase,Sucrase,Lactase,Absorbed by mucosal cells,Blood stream,麦芽糖,蔗糖,乳糖,Transform of carbohydrates in the liver,Fructose&galactose,Glucose,Cell,Energy,Glycogen,Blood vessels,Blood vessels,Excess glucose can be transformed and stored,as glycogen in liver and muscles,.,Our liver can store 70g(or 280 calories)of glycogen.,Our muscles can normally store about 120 g(or 480 cal)of glycogen.,Transform of carbohydrates in the liver,Liver glycogen,：,maintains,blood glucose levels,provide,the needs of our cells,including those of our,brain,spinal cord,and,red blood cell.,In addition,It provide energy to the muscles during,intense exercise,（剧烈运动）,.,We do not possess enzymes that can break down fiber.,Thus,fiber passes through the small intestine undigested and enters the large intestine or colon.,There is no any digested process for fiber。,Once into the large intestine,bacteria,break down some undigested carbohydrates,causing the production of,gas,and a few fatty,acids,（产酸,、,产气）,.,Digestion of carbohydrates in foods(In the large intestine),The cells of the large intestine use,these fatty acids for energy.,The,fiber remaining,in the colon adds bulk to our stools and,is excreted in feces.,Salivary amylase breaks down starch into shorter polysaccharides and a few maltose.,No digestion takes place,Pancreatic amylase is secreted into small intestine.,Majority of starch were digested.Pancreatic amylaseSpecific enzymes；All monosaccharides are absorbed by small intestine and enter bloodstream.,Monosaccharides travel to liver in bloodstream,then to cells to provide energy;,Excess glucose is stored as glycogen in liver.,Bacteria break down some undigested CHO;remaining fiber is excreted in feces,.,Summary,四,、,碳水化合物的功能,Function of carbohydrates,1.提供和贮存能量,（provide and store energy）,How much？,4kcal/g.,Some of our cells can also use fat and even protein for energy if necessary.,However,our,red blood cells,can utilize,only,glucose and our,brain,&other,nervous,tissues primarily rely on,glucose,.,Carbohydrate,Fat,Amounts of carbohydrate and fat used during the different extent of exercise.,Light,Moderate,Intense,67%,45%,13%,87%,55%,33%,Percent contribution to total energy,Fat,breakdown is a,slow,process and require oxygen,we can break down,glucose,very,quickly,either with or without oxygen.,Function of carbohydrates,2.节约蛋白质作用,(CHOs spare proteins),定义：,当摄入足够的碳水化合物时，可以防止体内和膳食中的,蛋白质转变为葡萄糖,.,糖异生,(gluconeogenesis),Gluconeo,genesis:,The generation of glucose from the breakdown of protein into amino acids.,When our body uses proteins for energy,the amino acids from these proteins cannot be used to,make,new,cells,repair,tissue damage,support,our immune system,or perform any of their other functions.,Using amino acids,in this manner,over a prolonged period of time,can cause,serious,possibly,irreversible,damage,to these organs.,3.,抗生酮作用,（Prevent the generation of ketones),Ketoacidosis,:,A condition in which,excessive,ketones,（酮体）,are present in the blood,causing the blood to become very,acidic,which alters basic body functions and damages tissues.,Function of carbohydrates,Low carbohydrate intake can lead to ketoaci,d,osis,(酮症酸中毒）,Thus,when carbohydrate intake is inadequate,our body seeks an alternative source of fuel for the brain and begins to break down stored,fat.,acetyl-CoA is the metabolites of fatty acid oxidation.,If inadequate carbohydrate intake continues for an extended period of time,excess acetyl-CoA can be converted to,ketones.,The high acidity of the blood interferes with basic body functions,causes the,loss of lean body mass,and,damages,many,body tissues,.,Where do ketones come from?,4.机体的构成成分,5.改变食物的色、香、味、型,6.提供膳食纤维,Functions of carbohydrates,五,、,碳水化合物代谢相关疾病,糖尿病,低血糖症,乳糖不耐症,Glucose molecules are too large to cross the cell membranes of our tissues independently.,To get in,glucose,needs assistance from the hormone,insulin,.,血糖的调节过程,Glucose in blood enters cells,Insulin stimulates glucose transport into cell,Insulin secreted by pancreas enters bloodstream,Tissue cell membrane,When blood glucose is high,Glucagon secreted by pancreas enters bloodstream,Glucagon stimulates glycogen breakdown,Glucose is secreted into bloodstream and transported to cells,Liver cell membrane,When blood glucose is low,胰高血糖素,Normally,insulin,and,glucagon,balance each other to maintain blood glucose within a healthy range.,If this balance is altered,it can lead to health conditions such as,diabetes,（糖尿病）,or,hypoglycemia,（低血糖症）,.,血糖指数,（Glycemic index，GI）,定义,：,50g,含碳水化合物的食物,血糖应答曲线下面积,与同一个体摄入,50g,碳水化合物的标准食物（葡萄糖或面包）血糖应答曲线下面积之比。,血糖指数是食物升高血糖潜力的一个参考指标，反应了食物对血糖的影响程度。,高,GI,食物能使血糖突然升高。,血糖指数的应用,指导合理膳食，有效控制血糖,糖尿病人,低血糖症患者,、,运动员,有助于控制体重,改善胃肠道功能,Lactose intolerance:,A disorder in which the body does not produce sufficient,lactase enzyme,（乳糖酶）,and therefore cannot digest foods that contain lactose,such as cows milk.,乳糖不耐症,（Lactose intolerance）,主要症状：,胃肠不适、胀气、痉挛和腹泻等。,It is estimated that up to,70%,of the worlds adult population suffer this disorder.,Not,everyone experiences lactose intolerance to the,same extent,(small amounts,not tolerant any),Lactose intolerance,Lactose intolerance should not be,confused with,a,milk allergy,.People who are allergic to milk experience an immune reaction to the proteins found in cows milk.,六、膳食参考摄入量Dietary reference intakes,中国营养学会推荐我国居民的碳水化合物的膳食推荐摄入量占总能量的,55%65%,。,食物,GI,食物,GI,食物,GI,大米饭,88,柚子,25,熟香蕉,52,酸奶,83,鲜桃,28,猕猴桃,52,牛奶,27.6,梨,36,芒果,55,鲜豆腐,31.9,苹果,36,菠萝,66,生香蕉,30,柑,43,西瓜,72,小结,碳水化合物的分类及功能,膳食纤维的定义及功能,乳糖不耐症,