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人从在母体内形成胎儿到生命终止,整个生命过程都需要营养。所谓营养是指食物中能维持人的生命,生长和正常生理功能所必需的各种有效成分。食物中营养素蛋白质、脂肪、碳水化合物、无机盐、维生素和水。蛋白质既是构成人体的结构材料,又是发挥生理作用的功能物质(人体的肌肉、血液、骨头、牙齿乃至各细胞的成分都需要蛋白质的参与),因此,人们说蛋白质是生命的基础,没有蛋白质就没有生命。在日常的食物中,猪肉、羊肉、牛肉、鱼、蛋、大豆都含有丰富的蛋白质,但能被人体吸收利用的不是蛋白质本身,而是把蛋白质消化分解成氨基酸后才能被人体收和利用。自然界的蛋白质由20多种氨基酸组成,这些氨基酸对人体都是不可缺少的。有些氨基酸人体内能够合成,有些则不能合成,那些人体内不能合成的氨基酸必需由食物提供,又被称为必需氨基酸,成人有8种氨基酸是必需的,即赖氨酸、色氨酸、蛋氨酸、苯丙氨酸、亮氨酸、异亮氨酸、苏氨酸、缬氧酸;组氨酸对婴幼儿也是必需的。这些氨基酸是婴幼儿生长发育不能少的。鸡蛋、牛奶、大豆均含有优质蛋白质,但每种食物蛋白质中所含的氨基酸量不一定包含了全部人
People from the fetus in the mother to the end of life, the whole process of life requires nutrition. The so-called nutrition refers to the food can maintain the life, growth and normal physiological functions necessary for a variety of active ingredients. Nutrients in food Proteins, fats, carbohydrates, inorganic salts, vitamins and water. Proteins are both structural materials that make up the human body and are functional substances that play a physiological role (proteins are involved in the body’s muscles, blood, bones, teeth, and even the components of every cell). Therefore, people say that protein is the basis of life and that no protein There is no life. In daily food, pork, lamb, beef, fish, eggs and soy are all rich in protein, but can not be absorbed by the body to use the protein itself, but the protein digested into amino acids before they can be received and used by the body. The nature of the protein by more than 20 kinds of amino acids, these amino acids are indispensable to the human body. Some amino acids can be synthesized in the human body, while others can not be synthesized. Those amino acids that can not be synthesized in the human body must be provided by food and are also called essential amino acids. Eight kinds of amino acids are necessary in adults, that is, lysine, tryptophan, methionine , Phenylalanine, leucine, isoleucine, threonine, valine; histidine is also essential for infants and young children. These amino acids are infants and young children growth and development can not be less. Eggs, milk and soy contain high quality protein, but the amount of amino acids contained in each food protein does not necessarily include all of them