讲授临床营养学第一次课

临床营养学,泸州医学院公共卫生营养与食品卫生教研室：谢惠波2014年秋,忠告：食物是最好的医药！,第二节 宏量营养素 一、蛋白质Protein,谢惠波2014年秋,主页目录-Home,含量：体重 16%19%更新： 动态平衡，不断更新，每天约3%，肠和骨髓最快。功能： 1.机体构成成分 2.构成各种生理活性物质和重要的生理功能 3.提供热能,人体中蛋白质,主页目录-Home,人体组织的构成成分 Required for building and repair of body tissues 构成各种生理活性物质和重要的生理功能 Enzymes, hormones, and many immune molecules are proteins. Essential body processes such as water balancing, nutrient transport, and muscle contractions require protein to function. 提供热能 Protein is a source of energy。肽、氨基酸特有的生理功能,1、 蛋白质功能Section 1 Functions of protein,主页目录-Home,2、蛋白质的组成,主要由碳、氢、氧、硫、氮等。有些还有磷、铁、锰、碘、锌等。蛋白质是人体中氮的唯一来源。大多数蛋白质的含氮量在16%，因此每克氮换算成蛋白质是6.25克。,3、蛋白质的分类参考蛋白、完全蛋白和蛋白质的互补作用,参 考 蛋 白,用于测定食物蛋白质质量的标准蛋白。 Reference Protein: A standard against which to measure the quality of other proteins.,完 全 蛋 白,必需氨基酸模式与人体蛋白质相对一致，能满足机体蛋白质合成需要的食物蛋白质。 Complete Protein: A dietary protein containing all the essential amino acids in relatively the same amounts that human being required. (including animal protein and soy protein ) Incomplete protein,蛋 白 质 互 补,将两种或两种以上的食物蛋白质混合事用，使不同食物中必需氨基酸以多补少，从而提高膳食蛋白质的营养价值。 Complementary Protein: Two or more proteins whose amino acids assortments complement each other in such a way that the essential amino acids missing from one are supplied by the other.,主页目录-Home,The first structure,蛋白质(protein),氨基酸（Amino acid, AA）,非必需AA(nonessential-)：9种 半必需AA（条件必需AA）：2种 （semi-,or conditionally-）必需AA（essentional-）：9种,多肽（poly-）10 AA以上寡肽（oligo-）410 AA以下 3肽（tri-）3AA 2肽（di-）2AA,肽(peptide),主页目录-Home,1. 种类：20种 (1) 必需AA（EAA） (2) 非必需氨基酸（NEAA） (3) 半必需氨基酸 ( semi-EAA or conditional EAA) 半胱酸（Cysteine）蛋氨酸（Methionine） 酪氨酸（Tyrosine）苯丙氨酸（Phenylalanine）2. 必需氨基酸： 人体不能合成或合成速度不能满足机体需要，必需从食物中直接获得的AA。 Amino acids that the body cannot synthesize in amount sufficient to meet physiological needs and has to obtain them from foods.,二、 氨基酸和必需氨基酸 Section 2 Amino acid and EAA,主页目录-Home,表 1-1 人体内的氨基酸,*组氨酸为婴儿必需氨基酸，成人需要量可能较少。 摘自Modern Nutrition in Health and Disease,第9版,第14页,1999。,主页目录-Home,氨基酸模式(AA Pattern)和限制氨基酸 (limiting AA),1. 氨基酸模式 (AA Pattern) ： 蛋白质中各种必需氨基酸的构成比例。,主页目录-Home,表1-2 几种食物和人体蛋白质氨基酸模式,数据摘自营养与食品卫生学，第3版，第9页。,主页目录-Home,限制氨基酸 （limiting amino acid）,与人体蛋白质模式比较，食物蛋白质中含量相对较低的必需AA。 The essential amino acid found in the shortest supply relative to the amount needed for protein synthesis in the body. FourAA are mostlikelytobe limiting: Lysine（赖），Methionine（蛋），Threonine（苏），Tryptophan（色） .,主页目录-Home,三、 蛋白质的消化、吸收和代谢,消化和吸收（digestion and absorption）,主页目录-Home,Gastric Juice : 1. Acid denaturation 2. 胃蛋白酶Pepsin在小肠进行吸收,dietary Protein,dipeptide , tripeptide and free AA,absorbed through the mucosal cells of small intestine 肽酶peptidase,through three active free AA transport systems neutral-,basic- and acidic-.,Liver and other organs,主页目录-Home,代谢与氮平衡 (metabolism and nitrogen balance),1.代谢,摄入蛋白质90克,消 化 道,(30%)肌肉,(50%)器官,体液,其它,机体蛋白质,氨基酸池,粪便,尿,其它,(20%),肠道内源性蛋白质70g,消化、吸收蛋白质150g,图1-1 蛋白质代谢及氮平衡,主页目录-Home,氮平衡（Nitrogen balance）,(1)必要的氮损失（obligatory nitrogen losses） (2) 氮平衡： BI（UFS）,Positive nitrogen balance,N in N out,N in = N out,Nitrogen equillibrium,Negativenitrogen balance,N in N out,主页目录-Home,四、 食物蛋白质营养学评价,(一)蛋白质含量 (content）,(2)表观消化率（apparent -）:,(二)蛋白质消化率(digestibility),(1)真消化率（true -）,主页目录-Home,(三)蛋白质利用率（utilization）,1.Biological value, BV:生物价,The amount of protein nitrogen that is retained for growth and maintenance,expressed as a percentage of the protein nitrogen that has been digested and absorbed. To determine the actual value of an absorbed protein as it is used by the body.,主页目录-Home,2.Amino Acid Score,AAS氨基酸评分,The lowest score is the score of limiting AA which is the AAS of the protein. A method of evaluating protein quality by comparing a test proteins amino acid pattern with that of a reference protein; sometimes called chemical scoring.,主页目录-Home,表1-4 几种食物和不同人群需要的氨基酸评分模式,摘自WTO Technical Report Series 724,第12页,1985年。,主页目录-Home,表1-5 常见几种食物蛋白质质量,摘自“营养与食品卫生学”，第3版，第11页。,主页目录-Home,表1-6 几种食物蛋白质的PDCAAS,摘自Understanding Nutrition, 第7版，第215页，1996年。,主页目录-Home,5、 高蛋白质膳食过多的危害problems of excess protein）,Adult Bone Loss (Osteoporosis骨质疏松): Calcium excretion rises as protein intake increases. Recommen-dation of calcium-to-protein is more than 20(mg) to 1(g).,Cancer: population studies suggest a correlation between high intakes of animal protein and some type cancer ( cancer of colon, breast,kidneys, pancreas, and prostate),Gain Weight: Protein-rich foods are often fat-rich foods. Others.,Heart Disease: Foods rich in animal protein tend tobe rich in saturated fats and cholesterol; homocystei（高半胱氨酸）may be an independent risk factor for heart disease.,主页目录-Home,6、蛋白质供给量和食物来源 （DRIs and Food source）,RNI: 1) 数量 2）质量 (优质蛋白质)Food Source: animal and plant foods. Milk and Soy been,主页目录-Home,中国居民膳食蛋白质的推荐摄入量: RNI与RDA,主页目录-Home,RNI与RDA：续表,主页目录-Home,Question,What is the difference between esse