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1、第一章第一章 营养学基础营养学基础碳水化合物碳水化合物CarbohydratesMain contents nDefinition of carbohydratesnClassification of carbohydratesnDigestion & absorption of CHOnFunctions of carbohydratesnDisorders related to CHO metabolismnDietary reference intakes of CHOs|Carbohydrates are one of the three macronutrient types tha
2、t 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，主碳水化合物：属三大能量营养素之一，主要由碳、氢、氧构成。要由碳、氢、氧构成。 一一、碳水化合物的定义碳水化合物的定义 What are carbohydrates?|Carbohydrate can be abbreviated as “CHO”.|We obtained carbohydrates predominantly from plant foods such as fruits,
3、vegetables, and grain.Why?Plants make carbohydrates through the process of photosynthesisEnergy from sunCarbon dioxide from airGlucose stored in plantWaterWater+ Carbon dioxideGlucose光合作用光合作用二、碳水化合物的分类二、碳水化合物的分类Classification of carbohydratesCarbohydratesSimpleComplexDisaccharidesMonosaccharidePolys
4、accharidesOligosaccharide寡糖寡糖单糖单糖双糖双糖多糖多糖HOHCH2OHHOHOHHOHHHGlucoseOHOHHOHHOHCH2OHCH2OHFructoseHOOHOHOHHHHHCH2OHGalactoseThe three most common monosaccharides. ALL of them contain identical atomsStructure of monosaccharidesMonosaccharides-Glucose（葡萄糖）（葡萄糖）|Glucose is the most abundant sugar molecule
5、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
6、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。优先为大脑提供能量。Monosaccharides-Fructose（果糖）（果糖）|Fructose is also called fruit sugar.|Fructose is the sweetest natural sugar, occurs naturally in fruits and vegetables. PrefixMonosaccharides-Galactose（半乳糖）（半乳糖）|Galactose does not occur alone in foods. It joins with glucose to
7、 create lactose, one of the disaccharides.Sweetest monosaccharides?The most abundant monosaccharides ?The sweetest：fructoseThe most abundant：glucose Disaccharide（双糖）（双糖）|Disaccharide: A carbohydrate compound consisting of two sugar molecules joined together.The three most common disaccharides found
8、in foods are lactose（乳糖）（乳糖）, maltose （麦芽糖）（麦芽糖）, and sucrose （蔗糖）（蔗糖）.Disaccharides Lactose（乳糖）（乳糖）GlucoseGalactoseLactose| Lactose: Consist of one glucose molecule and one galactose ( (半乳糖）半乳糖） molecule.DisaccharidesMaltose （麦芽糖）（麦芽糖）|Maltose: also called malt sugar, consist of two molecules of gl
9、ucose.| It does not generally occur by itself in foods, but results as a by-product of digestion.GlucoseDisaccharidesSucrose（蔗糖）（蔗糖）vSucrose is composed of one glucose molecule and one fructose（果糖）（果糖） molecule. vSucrose provides much of the sweet taste found in honey, fruits, and vegetables.How abo
10、ut the Sucrose and fructose?vSweeter than lactose or maltose, why?哪种双糖最甜哪种双糖最甜-麦芽糖，蔗糖，乳糖？麦芽糖，蔗糖，乳糖？麦芽糖麦芽糖-2个葡萄糖个葡萄糖蔗糖蔗糖-1个葡萄糖个葡萄糖+1个果糖个果糖乳糖乳糖-1个葡萄糖个葡萄糖+1个半乳糖个半乳糖蔗糖蔗糖Oligosaccharide（寡糖）（寡糖）vOligosaccharide are composed of 3 to 10 monosaccharides.vThe most common oligosaccharides are raffinose （棉籽糖）（棉
11、籽糖）and stachyose（水苏糖）（水苏糖）. v They can not be degraded by enzymes in the small intestine, but can be broke down in the large intestine.Polysaccharides（多糖）（多糖）Polysaccharides include starch（淀粉）（淀粉）, glycogen（糖原）（糖原） and most fibers（纤维）（纤维）.PolysaccharidesStarchGlycogenFiber淀粉淀粉糖原糖原纤维纤维Polysaccharide-
12、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）（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 ea
13、sily digest most starches， we call them digestible starch(可吸收淀粉）可吸收淀粉）.|根据其结构可分为直链淀粉根据其结构可分为直链淀粉（amylose）和支链和支链淀粉淀粉（amylopectin），），前者易使食物老化，后前者易使食物老化，后者易使食物糊化者易使食物糊化（gelatinization ）。|However, some starch in plants is not digestible and is called resistant starch（抗性淀粉）（抗性淀粉）.|抗性淀粉：指健康者小肠中不吸收的淀抗性淀粉：指
14、健康者小肠中不吸收的淀粉及其降解产物。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.| 豆科食物豆科食物（Legumes）含有的抗性淀粉比含有的抗性淀粉比谷类谷类、蔬菜和水果多。蔬菜和水果多。Bean sprou
15、tGreen 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）（糖原）Which tissues are abundant in glycogen?We store glycogen in our muscles and liver. We can break do
16、wn 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）（不溶性纤维）: cellulose（纤（纤维素）维素）, hemicellulose（半纤维素）（半纤维素） and xylogen（木质素）（木质素）. .|Soluble fibers（可溶性纤维）（可溶性纤维）
17、: :果胶果胶（pectin) ，树胶和粘胶树胶和粘胶. . Polysaccharide-Fiber|膳食纤维膳食纤维（dietary fiber）：是指植物性：是指植物性食物或原料中糖苷键大于食物或原料中糖苷键大于3个，不能被人个，不能被人体小肠消化和吸收，但对人体健康有意义体小肠消化和吸收，但对人体健康有意义的碳水化合物。的碳水化合物。|膳食纤维包括部分非淀粉多糖（纤维素、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）、半纤维素、木质素、果胶等）、抗性淀粉抗性淀粉、葡聚糖葡聚糖以及以及部分低聚糖部分低聚糖等。等。 (1)(1)增强肠道功能、有利粪便排出增强肠道功能、有利粪
18、便排出 Helps prevent constipation and other intestinal problems by keeping our stools moist and soft.Functions of dietary fiberDietary fiber increases faecal bulk through water binding by fiber.Fiber gives gut muscles“something to push” and makes it easier to eliminate stools. (2) 控制体重和减肥控制体重和减肥 May en
19、hance 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)(3) 降低血糖和血胆固醇降低血糖和血胆固醇Decrease the level of blood sugar and cholesterol May reduce the risk
20、 of heart disease by delaying or blocking the absorption of dietary cholesterol into the bloodstream. (4)(4) 降低结肠癌的发病风险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 s
21、peeds their elimination from the colon. 三、碳水化合物的消化及吸收三、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 con
22、verted to glucose.Digestion of carbohydrates in foods (In the mouth)CHO digestion begins in the mouth.Question: When you eat steamed bread（馒头）（馒头）, notice that you can actually taste it becoming sweeter, Why?Saliva amylase（淀粉酶）（淀粉酶） breaks starch( (淀粉）淀粉） into smaller particles and eventually into t
23、he maltose（麦芽糖）（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 salivary amylase enzyme.Would you guess the reasons?|The majority of carbohyd
24、rate 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）（麦芽糖）.Additional enzymes found in the intestina
25、l tract break down disaccharides into monosaccharides. MaltoseSucroseLactoseGlucoseGlucose & FructoseGlucose & GalactoseMaltaseSucraseLactaseAbsorbed by mucosal cellsBlood stream麦芽糖麦芽糖蔗糖蔗糖乳糖乳糖Transform of carbohydrates in the liverFructose&galactoseGlucoseCellEnergyGlycogenBlood vesselsBlood vessels
26、|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 t
27、he 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）（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
28、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（产酸、产气）产气）.Digestion of carbohydrates in foods (In the large intestine)|The cells of the large intest
29、ine 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 placePancreatic amylase is secreted into small intestine.Majority of starch we
30、re 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
31、fiber is excreted in feces.Summary四四、碳水化合物的功能碳水化合物的功能Function of carbohydrates1.1.提供和贮存能量提供和贮存能量（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 nervo
32、us tissues primarily rely on glucose.CarbohydrateFatAmounts of carbohydrate and fat used during the different extent of exercise.LightModerate Intense67%45%13%87%55%33%Percent contribution to total energynFat breakdown is a slow process and require oxygennwe can break down glucose very quickly eithe
33、r with or without oxygen.Function of carbohydrates2.2.节约蛋白质作用节约蛋白质作用 (CHOs spare proteins)定义：定义：当摄入足够的碳水化合物时，可以防止体当摄入足够的碳水化合物时，可以防止体内和膳食中的内和膳食中的蛋白质转变为葡萄糖蛋白质转变为葡萄糖. .糖异生糖异生(gluconeogenesis)Gluconeogenesis: The generation of glucose from the breakdown of protein into amino acids.|When our body uses pr
34、oteins 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
35、 organs.3.抗生酮作用抗生酮作用（Prevent the generation of ketones)|Ketoacidosis: A condition in which excessive ketones（酮酮体体） are present in the blood, causing the blood to become very acidic, which alters basic body functions and damages tissues.Function of carbohydratesLow carbohydrate intake can lead to ket
36、oacidosis( (酮症酸中毒）酮症酸中毒）nThus, when carbohydrate intake is inadequate, our body seeks an alternative source of fuel for the brain and begins to break down stored fat.n acetyl-CoA is the metabolites of fatty acid oxidation.nIf inadequate carbohydrate intake continues for an extended period of time, e
37、xcess acetyl-CoA can be converted to ketones.nThe 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?4.4.机体的构成成分机体的构成成分5.5.改变食物的色、香、味、型改变食物的色、香、味、型6.6.提供膳食纤维提供膳食纤维Functions of carbohydrates五五、碳水化
38、合物代谢相关疾病碳水化合物代谢相关疾病n糖尿病糖尿病n低血糖症低血糖症n乳糖不耐症乳糖不耐症|Glucose molecules are too large to cross the cell membranes of our tissues independently.| To get in, glucose needs assistance from the hormone insulin.血糖的调节过程血糖的调节过程Glucose in blood enters cellsInsulin stimulates glucose transport into cellInsulin secr
39、eted by pancreas enters bloodstreamTissue cell membraneWhen blood glucose is highGlucagon secreted by pancreas enters bloodstreamGlucagon stimulates glycogen breakdownGlucose is secreted into bloodstream and transported to cellsLiver cell membraneWhen blood glucose is low胰高血糖素胰高血糖素|Normally, insulin
40、 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）（糖尿病） or hypoglycemia（低血糖症）（低血糖症）.血糖指数血糖指数（Glycemic index，GI）n定定义义：50g50g含含碳碳水水化化合合物物的的食食物物血血糖糖应应答答曲曲线线下下面面积积与与同同一一个个体体摄摄入入50g50g 碳碳水水
41、化化合合物物的的标标准准食食物物（葡萄糖或面包）血糖应答曲线下面积之比。（葡萄糖或面包）血糖应答曲线下面积之比。n血血糖糖指指数数是是食食物物升升高高血血糖糖潜潜力力的的一一个个参参考考指指标标，反应了食物对血糖的影响程度。反应了食物对血糖的影响程度。n 高高GIGI食物能使血糖突然升高。食物能使血糖突然升高。血糖指数的应用血糖指数的应用n指导合理膳食，有效控制血糖指导合理膳食，有效控制血糖 糖尿病人糖尿病人 低血糖症患者低血糖症患者、运动员运动员n有助于控制体重有助于控制体重n改善胃肠道功能改善胃肠道功能nLactose intolerance: A disorder in which th
42、e body does not produce sufficient lactase enzyme（乳乳糖糖酶酶）and therefore cannot digest foods that contain lactose, such as cows milk.乳糖不耐症乳糖不耐症（Lactose intolerance）n主要症状：主要症状：胃肠不适、胀气、痉挛和腹泻等。胃肠不适、胀气、痉挛和腹泻等。 nIt is estimated that up to 70% of the worlds adult population suffer this disorder.nNot everyon
43、e experiences lactose intolerance to the same extent (small amounts, not tolerant any)Lactose intoleranceLactose 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、膳食参考摄入量六、膳食参考摄入量Dietary reference intakesn 中国营养学会推荐我国居民的碳水化合物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的膳食推荐摄入量占总能量的55%65%。食物食物GI食物食物GI食物食物GI大米饭大米饭88柚子柚子25熟香蕉熟香蕉52酸奶酸奶83鲜桃鲜桃28猕猴桃猕猴桃52牛奶牛奶27.6梨梨36芒果芒果55鲜豆腐鲜豆腐 31.9苹果苹果36菠萝菠萝66生香蕉生香蕉30柑柑43西瓜西瓜72小结小结n碳水化合物的分类及功能碳水化合物的分类及功能n膳食纤维的定义及功能膳食纤维的定义及功能n乳糖不耐症乳糖不耐症
