首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
Human Nutrition and Diet The scope of human nutrition extends far beyond the classical study of the physiological and bioche
Human Nutrition and Diet The scope of human nutrition extends far beyond the classical study of the physiological and bioche
admin
2010-07-14
34
问题
Human Nutrition and Diet
The scope of human nutrition extends far beyond the classical study of the physiological and biochemical processes involved in nourishment; i.e. , how substances in food are converted into energy and body tissues. Human nutrition has come to involve all the effects on humans of any component found in food; these include most chronic degenerative diseases (dental decay, coronary heart disease, some cancers, etc. ), which are now major targets of research activity. The scope of nutrition extends to the effects of food on human function; e.g. , mental function, athletic performance, resistance to infection, and fetal health and development. There is a growing interaction between nutritional science and genetics because of the diversity of human chemical make-up and because food components of which most people are unaware can have marked effects on some individuals. Last, nutrition also considers why people choose to eat the foods they do, even after they have been advised that doing so may be unhealthy. The study of food habits and people’s attitudes, beliefs, likes, and dislikes overlaps with the social sciences of physiology, anthropology, sociology, and economics. Dietetics is the application of nutrition in the health sciences.
The principal evidence that an organic compound is essential is that it consistently cures a specific deficiency disease. An inorganic clement is essential if it regularly occurs in the body and is demonstrated to have a function (such as being an integral part of an enzyme). Humans require oxygen, water, food energy, protein, 14 other organic compounds (vitamins and essential fatty acids), and some 18 inorganic elements, as well as carbon, hydrogen, and nitrogen.
Growing children need more protein per kilogram of body weight than do adults. Protein requirement at all ages is increased by infections not only because there is an increased utilization of protein but also because illness usually impairs the appetite and thus reduces dietary intake of all substances, including protein. In many countries children are weaned on a diet of cereal paps with little or no supplement of milk or other protein containing foods. Such a diet at the least retards growth and development. If a child on such a diet suffers from an acute infection, notably measles or gastroenteritis (胃肠炎), a severe illness may ensue. The death rate from protein-calorie malnutrition in many poverty stricken communities is high. Primary protein deficiency is not common among adults, for whom cereals in general satisfy the protein requirement.
Iron is required for the synthesis of hemoglobin (血红蛋白), the oxygen-binding pigment in red blood ceils. Normally the iron liberated from old ceils is retained and can be reutilized. When, however, there is chronic bleeding from wounds or there is severe and prolonged menstruation, the normal amount of dietary iron may be insufficient to replenish the body’s supply. Losses of iron in the menses, the needs of a fetus, and the inevitable loss at labour and in the milk of a lactating (哺乳期的) woman increase the iron requirements of women during their reproductive life.
Calcium is the most obvious and persistent of the mineral nutrients, yet it is more difficult to measure the adequacy of its intake than for other nutrients. More than 99 percent of the body’s calcium is in the skeleton, where it not only provides structural support but also is a large reservoir for maintaining a constant calcium concentration in plasma. Several hormones are all involved in this regulation. The amount of calcium in the bones is nearly 30 grams at birth and builds up to about 1,200 grams in an adult. Hence, an average of 180 milligrams of calcium must be retained in the body throughout childhood, and the individual daily amounts should reach 400 milligrams during the adolescent growth spurt. Absorption of calcium, like that of many other metallic elements, is inefficient. The diet must therefore supply more calcium than the amount theoretically retained for skeletal growth. Three major questions about calcium are as yet not fully answered by nutritional science: (1) whether generous intakes of calcium during childhood and adolescence will lead to taller adults or heavier bones, (2) whether a generous intake of calcium from about 45 years of age will delay the progress of osteoporosis (骨质疏松), which occurs in older people and is more likely to cause symptoms in women after menopause (更年期), and (3) what mechanisms enable people in Africa, for example, who grow up on cereal diets low in calcium, to retain enough calcium to achieve a skeleton of similar height to those in northern countries where milk and cheese (both rich in calcium) are staples in the diet.
Sodium is present only in small quantities in most natural foods, but salt is added, often in large amounts, in food processing and by cooks to enhance flavour. Sodium is the predominant ion in extracellular fluid; an excess can cause edema (水肿), especially in conditions such as congestive heart failure. A low sodium intake leads to a lowering of the blood pressure and brings about diuresis (利尿), ridding the body of the excess extracellular fluid. There is now much evidence that excess dietary salt may contribute to high blood pressure in some individuals, but other factors are also responsible.
For normal nutrition and metabolism the body requires certain organic substances, called vitamins, which it cannot make for itself, at least in sufficient quantities. Many of them function as components of enzyme systems. Because they are required in such small quantities, vitamins do not contribute significantly to the energy needs of the body. In their absence, however, the carbohydrates, fats, and proteins required for energy production and tissue maintenance cannot be properly metabolized. Vitamins were originally identified by letters as each new one was discovered, but this method is being replaced as the vitamins become known by their chemical names.
Nutritional science ______ three major questions about calcium.
选项
答案
has not fully answered
解析
文章第五自然段最后一句说明此点。营养科学尚未能完全解答有关人体钙含量的三个问题。
转载请注明原文地址:https://kaotiyun.com/show/FdKK777K
0
大学英语六级
相关试题推荐
SinceIboughtacomputerlastmonth,anewworldhasopenedupbeforeme,aworldthatreachesfarbeyondmyimmediatesurroun
SinceIboughtacomputerlastmonth,anewworldhasopenedupbeforeme,aworldthatreachesfarbeyondmyimmediatesurroun
SinceIboughtacomputerlastmonth,anewworldhasopenedupbeforeme,aworldthatreachesfarbeyondmyimmediatesurroun
SinceIboughtacomputerlastmonth,anewworldhasopenedupbeforeme,aworldthatreachesfarbeyondmyimmediatesurroun
SinceIboughtacomputerlastmonth,anewworldhasopenedupbeforeme,aworldthatreachesfarbeyondmyimmediatesurroun
SinceIboughtacomputerlastmonth,anewworldhasopenedupbeforeme,aworldthatreachesfarbeyondmyimmediatesurroun
A、Apieceofcake.B、JustOK.C、Abitbeyondhim.D、Alittleeasierforhim.B
THEPARTYGENEStevenBennerjokinglycallshimselfadilettante(业余艺术好爱者).AbiochemistattheUniversityofFloridainGai
随机试题
我国专利法对发明和实用新型采用的新颖性标准是
A、预防孕母各种感染和接触有害物质B、加强护理、保暖、喂养和预防感染C、合理喂养、培养良好习惯和计划免疫D、重视早期教育和培养能力E、保证充足营养,加强体格锻炼和品德教育婴幼儿期的保健重点是()
A、阿霉素B、环磷酰胺C、博来霉素D、顺铂E、L-门冬酰胺酶具有肺部毒性,表现为肺炎性病变和肺纤维化的药物为( )。
关于监狱在刑事诉讼中的职权,下列哪一选项是正确的?(2016年卷二23题)
某岩体的岩石单轴饱和抗压强度为10MPa,在现场做岩体的波速试验vpm=4.0km/s,在室内对岩块进行波速试验vpr=5.2km/s,如不考虑地下水、软弱结构面及初始应力的影响,按《工程岩体分级标准》(GB50218—94)计算岩体基本质量指标BQ值
机械失效安全和定位安全都属于机械本质安全设计的范畴,下列做法中,不属于机械失效安全设计的是()。
检验批质量验收合格应符合的规定不包括()。
某县工商局根据A企业的申请,依法向其颁发了营业执照。在一次联合执法检查中,该县工商局和地方税务局发现A企业在生产经营中有违法经营行为,同时违反了工商和税收有关法规。县工商局决定暂扣A企业的营业执照;县地方税务局则作出决定责令A企业补缴税款并加收滞纳金,同时
在制定运输价格时,政府指导价体现了统一性与灵活性相结合的原则,允许经营在规定范围和幅度内调价。()
甲看到卖淫女乙(12岁)长得极其娇嫩,觉得乙可能不满14周岁,便问其年龄,乙说自己今年16岁,甲心存怀疑但仍然与乙发生性关系,并多给1000元小费。关于甲的行为说法正确的是()
最新回复
(
0
)