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1、第一章 营养学基础,碳水化合物 Carbohydrates,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 e
2、nergy 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?,Plants make carbohyd
3、rates through the process of photosynthesis,Energy from sun,Carbon dioxide from air,Glucose stored in plant,Water,Water+ Carbon dioxide,Glucose,光合作用,二、碳水化合物的分类 Classification of carbohydrates,双糖,多糖,The three most common monosaccharides. ALL of them contain identical atoms,Structure of monosaccharide
4、s,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 f
5、or 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-Fructose（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 join
6、s with glucose to create lactose, one of the disaccharides.,Sweetest monosaccharides? The most abundant monosaccharides ?,The sweetest：fructose The most abundant：glucose,Disaccharide（双糖）,Disaccharide: A carbohydrate compound consisting of two sugar molecules joined together.,The three most common di
7、saccharides found in foods are lactose（乳糖）, maltose （麦芽糖）, and sucrose （蔗糖）.,Disaccharides Lactose（乳糖）,Lactose: Consist of one glucose molecule and one galactose (半乳糖） molecule.,DisaccharidesMaltose （麦芽糖）,Maltose: also called malt sugar, consist of two molecules of glucose. It does not generally occ
8、ur by itself in foods, but results as a by-product of digestion.,Glucose,DisaccharidesSucrose（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 th
9、an 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
10、 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
11、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（
12、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 s
13、uggested 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
14、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）, hemicellul
15、ose（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 constipation and other intestinal problems by keeping our st
16、ools 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 cholest
