8.10 营养适应
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Got Lactase?
::有乳腺吗?Do you remember this “got milk?” slogan from the 1990s? It was used in ads for milk in which celebrities were pictured wearing milk “mustaches.” While the purpose of the “got milk?” ads was to sell more milk, there is no denying that drinking milk can actually be good for one’s health. Milk is naturally high in and minerals . It can also be low in fat or even fat-free if treated to remove the that naturally occur in milk. However, before you reach for a tall, cold glass of milk, you might want to ask yourself another question: “got lactase?”
::你还记得1990年代的这个“牛奶? ” 口号吗? 该口号是用来做牛奶广告的? 该口号是用来做广告的,在牛奶广告中,名人被描绘成穿着牛奶的“奶 ” 。 虽然“牛奶? ” 广告的目的是要卖更多的牛奶,但不可否认,饮用牛奶对人的健康是有好处的。 牛奶自然是高含量和矿物质。 如果用它去掉牛奶中自然产生的牛奶,它也可能是低脂肪甚至无脂肪的。 然而,在你找到高杯、冷杯牛奶之前,你可能还要问自己另一个问题 : “ 有乳吗? ” 。Adaptation to Lactose
::适用于 Lactose 的适应Do you drink milk? Or do you avoid drinking milk and consuming milk products because they cause you discomfort? If the latter is the case, then you may have trouble digesting milk.
::究竟是你们饮乳呢?还是你们因乳汁和乳汁,而不饮奶呢?还是因乳汁和乳汁,而使你们感到不适呢?如果乳汁和奶水,你们或许因乳汁的消化而烦恼。Milk, Lactose, and Lactase
::牛奶、乳糖和乳酶Milk naturally contains more than just proteins and lipids — it also contains . Specifically, milk contains the sugar lactose , which is a disaccharide (two-sugar) compound that consists of one molecule each of galactose and glucose , as shown in the structural formula . Lactose makes up between two and eight percent of milk by weight. The exact amount varies both within and between .
::牛奶自然含有的不仅仅是蛋白质和脂质——它也包含。具体地说,牛奶含有糖乳糖,这是一种分酸(两糖)化合物,如结构公式所示,每颗白化糖和葡萄糖一个分子组成。乳糖按重量计算占牛奶的2%至8%。确切数量在内部和之间不尽相同。Each molecule of lactose consists of one molecule of galactose (left) and one molecule of glucose (right).
::乳糖的每一个分子由一个阴极(左)分子和一个葡萄糖(右)分子组成。Lactose in milk must be broken down into its two component sugars to be absorbed by the . The lactase is needed for this process, as shown in the diagram . Human infants are almost always born with the ability to synthesize lactase. This allows them to readily digest the lactose in their mother’s milk (or infant formula). I n the majority of infants, however, lactase synthesis begins to decline at about two years of age, and less and less lactase is produced throughout childhood .
::乳糖中的乳糖必须分为两种成分的糖,由乳糖吸收。 这一过程需要乳糖,如图所示。 人类婴儿几乎总是在出生时能够合成乳糖。 这使得他们能够很容易地消化母乳(或婴儿配方)中的乳糖。 然而,在大多数婴儿中,乳糖合成在大约两岁时开始下降,在整个童年中产的乳糖也越来越少。The enzyme lactase is needed to break down the milk sugar lactose into its galactose and glucose components.
::需要酶乳酶来将奶糖乳甘甘甘糖分解成其阴极糖和葡萄糖成分。Lactose Intolerance
::活性不容忍Lactose intolerance is the inability of older children and adults to digest lactose in milk. People who are lactose intolerant may be able to drink small quantities of milk without any problems, but if they try to consume larger amounts, they are likely to suffer adverse effects. For example, they may have abdominal bloating and cramping, flatulence (gas), diarrhea, nausea, and vomiting. The symptoms may occur from 30 minutes to two hours after milk is consumed, and they're generally worse when the quantity of milk consumed is greater. The symptoms result from the small intestine's inability to digest and absorb lactose, so the lactose is passed on to the , where normal intestinal start breaking it down through the process of . This process releases gas and causes the other symptoms of lactose intolerance.
::乳糖不耐症者可以无任何问题地喝少量牛奶,但如果他们试图消费大量奶的话,他们可能会受到不利影响,例如,他们可能患有腹部肿胀和腹部抽搐、扁肿(气)、腹泻、恶心和呕吐。症状可能发生在牛奶消耗后30分钟到2小时之间,通常当牛奶消耗量更大时更严重。小肠肠无法消化和吸收乳糖导致症状,因此甘蔗传播到正常肠胃开始通过消化过程破裂。这一过程释放气体,并造成其他乳糖不耐症症状。Lactose intolerance is actually the original and normal condition of the human species, as well as all other mammalian species. Early humans were hunter-gatherers that subsisted on wild plant and foods. The animal foods may have included meat and eggs , but did not include milk because animals had not been domesticated. Therefore, beyond the weaning period, milk was not available for people to drink in early human . It makes good biological sense to stop synthesizing an enzyme that the body does not need. After a young child is weaned, it is a waste of materials and energy to keep producing lactase when milk is no longer likely to be consumed.
::事实上,乳糖不耐症是人类以及所有其他哺乳动物物种的原始和正常状况。早期人类是野生植物和食物所依赖的狩猎采集器。动物食品可能包括肉类和蛋类,但因动物没有被驯化而不包括牛奶。因此,除断奶期外,人们不能在早期饮用牛奶。停止合成人体不需要的酶是良好的生物意义。在幼儿断奶后,在牛奶不再可能消耗时,继续生产乳腺是一种材料和能量的浪费。Overall, an estimated 60 percent of the world’s adult is thought to be lactose intolerant today. You can see the geographic distribution of modern human lactose intolerance on the map . Lactose intolerance (dark blue) approaches 100 percent in populations throughout southern South America, southern Africa, and East and Southeast Asia.
::总的说来,今天全世界估计有60%的成年人被认为患有乳糖不耐受症。 你可以在地图上看到现代人类乳糖不耐受症的地理分布。 在南美洲南部、南部非洲以及东亚和东南亚,乳糖不耐受症(黑蓝色)接近100%的人口。Worldwide distribution of lactose intolerance in human populations
::人类中乳糖不容异性在世界各地的分布情况Lactose intolerance is not considered a medical problem, because its symptoms can be avoided by avoiding milk or milk products. Dietary control of lactose intolerance may be a matter of trial and error, however, because different people may be able to consume different quantities of milk before symptoms occur. If you are lactose intolerant, be aware that low-fat and fat-free milk may contain somewhat more lactose than full-fat milk because the former often have added milk solids that are relatively high in lactose.
::乳糖不耐症不被视为医学问题,因为其症状可以通过避免牛奶或奶制品来避免。 但是,乳糖不耐症的饮食控制可能是一个尝试和错误问题,因为不同的人可能能够在出现症状之前消费不同数量的牛奶。 如果你对乳糖不耐症,请注意低脂肪和无脂肪牛奶中含的乳糖可能比全脂牛奶中含的乳糖多一些,因为乳糖中添加的乳糖固体通常相对较高。Lactase Persistence
::Lactase 持久性Lactase persistence is the opposite of lactose intolerance. People who are lactase persistent continue to produce the enzyme lactase beyond and generally throughout life. As a consequence they are able to digest lactose and drink milk at older ages without adverse effects. The map above can also be read to show where lactase persistence occurs today. Populations with a low percentage of lactose intolerance (including most North Americans and Western and Northern Europeans) have high percentages of lactase-persistent people.
::乳糖酶持久性与乳糖不耐受性相反,乳糖持久性的人继续在整个生命期之外和整个生命期生产酶乳酶,因此他们能够在没有不利影响的情况下消化乳糖和喝牛奶。上面的地图还可以读出来,以显示乳糖不耐性现在在哪里发生。乳糖不耐性比例低的人口(包括大多数北美人以及西欧和北欧人)有较高的乳糖耐性人口比例。Lactase persistence is a uniquely human trait that is not found in any other mammalian species. Why did lactase persistence evolve in humans? When some human populations began domesticating and keeping herds of animals, animal milk became a potential source of food . Animals such as cows, sheep, goats, camels, and even reindeer (see photo ) can be kept for their milk. These animal milks also contain lactose, so would be strong for any individuals who kept producing lactase beyond infancy and could make use of this nutritious food. Eventually, the trait of lactase persistence would increase in frequency and come to be the predominant trait in dairying populations.
::乳腺持久性是一种独特的人类特征,在任何其他哺乳动物物种中都找不到。为什么乳腺持久性在人类中演变?当某些人类开始驯化和保留动物群时,动物奶便成为潜在的食物来源,牛、绵羊、山羊、骆驼甚至驯鹿(见照片)等动物可以留作奶品。这些动物奶品中也含有乳糖,对于任何在婴儿以外生产乳腺并能够使用这种营养食品的人来说,乳腺持久性会强大。最终,乳房持久性的特征会增加频率,成为奶制品人群的主要特征。Sami (or Laplander) people in northern Scandinavia are traditional reindeer herders, and they are nearly 100 percent lactase persistent. This photo of a Sami man and his daughter on a reindeer was taken in 1900. Few Sami still herd reindeer today, but their lactase persistence has persisted.
::北斯堪的纳维亚北部的萨米人(或拉普兰德人)是传统的驯鹿牧民,他们有近100%的乳腺持久性。 1900年拍摄了一名萨米人及其女儿在驯鹿上的照片。 如今,少数萨米人仍在放牧驯鹿,但其乳腺持久性依然存在。It is likely that lactase persistence occurs as a result of both genes and environment. Some people inherit genes that help them keep producing lactase after infancy. Geneticists think that several different for lactase persistence arose independently in different populations within the last ten thousand years. Part of lactase persistence may be due to continued exposure to milk in the childhood and diet. In other words, a person may be genetically predisposed to synthesize lactase at older ages because of a mutation, but they may need the continued stimulation of milk drinking to keep producing lactase.
::遗传学家认为,过去一万年中,不同人群的乳腺持久性各不相同。乳腺持久性的部分原因可能是儿童时期和饮食中继续接触牛奶。换句话说,由于突变,一个人可能在遗传上容易在年长时合成乳腺,但是他们可能需要持续的牛奶饮料刺激,以保持乳腺的生长。Thrifty Gene or Drifty Gene?
::松动基因还是飘忽不定基因?Besides variation in lactase persistence, human populations may vary in how efficiently they use calories in the foods they consume. People in some populations seem able to get by on quantities of food that would be inadequate for others, so they tend to gain weight easily. What explains these differences in people?
::除了乳腺持久性的差异外,人类在消费的食品中使用卡路里的效率可能各有不同。 某些人口中的人似乎能够依靠对其他人来说不够的粮食数量获得食物,因此他们往往容易地增加体重。 是什么原因解释了人类中的这些差异?Thrifty Gene Hypothesis
::短短基因假说In 1962, human geneticist James Neel proposed the thrifty gene hypothesis . According to this hypothesis, so-called “thrifty genes” evolved in some human populations because they allowed people to get by on fewer calories and store the rest as body fat when food was plentiful. According to Neel’s hypothesis, thrifty genes would have increased in frequency through natural selection, because they would help people survive during times of famine. People with the genes would be fatter and able to rely on their stored body fat for calories when food was scarce.
::1962年,人类基因学家詹姆斯·内尔提出了节约基因假设。 根据这一假设,所谓的“极端基因 ” ( riftty genes ) 在一些人中演变为“极端基因 ” , 因为他们允许人们通过较少的热量获取食物,并在食物充足时将其余的作为脂肪储存起来。 根据尼尔的假设,通过自然选择,节约基因会增加频率,因为这样可以帮助人们在饥荒时期生存。 拥有这些基因的人会更胖,在食物稀缺时能够依靠储存的脂肪获取热量。Such thrifty genes would have been advantageous in early human populations of hunter-gatherers if food scarcity was a recurrent stress. However, in modern times, when most people have access to enough food year-round, thrifty genes would no longer be advantageous. In fact, under conditions of plentiful food, having thrifty genes would predispose people to gain weight and develop obesity . They would also tend to develop the chronic diseases associated with obesity, particularly type II . Diabetes mellitus is a disease that occurs when there are problems with the pancreatic insulin , which normally helps take up glucose from the and controls blood glucose levels. In type II diabetes, become relatively resistant to insulin, leading to high blood glucose. This causes symptoms like excessive thirst and urination . Without treatment, diabetes can lead to serious consequences, such as blindness and kidney failure .
::如果粮食短缺是一种经常性的压力,这种节食基因对早期的狩猎-采集者人口有好处;然而,在现代,当大多数人全年都能获得足够的食物时,节食基因将不再有利;事实上,在丰盛的食物条件下,拥有节食基因会使人容易变胖和发肥胖症;它们还倾向于发展与肥胖有关的慢性疾病,特别是第二类。糖尿病是一种在胰岛素出现问题时发生的疾病,通常有助于从血液中提取葡萄糖和控制血糖水平。在二类糖尿病中,对胰岛素的抗性较强,导致高血糖。这会造成诸如过量的口渴和尿等症状。不治疗,糖尿病会导致严重的后果,如失明和肾衰竭。Neel proposed his thrifty gene hypothesis not on the basis of genetic evidence for thrifty genes, but as a possible answer to the mystery of why genes that seem to promote diabetes have not been naturally selected out of some populations. The mystery arose from observations that certain populations — such as South Pacific Islanders, sub-Saharan Africans, and southwestern Native Americans — developed high levels of obesity and diabetes after they abandoned traditional diets and adopted Western diets. This is reflected in the 2005 death rates from diabetes in the U.S. population, as shown in the graph The single largest group in the U.S. population is the “white” group, but they had the second lowest number of diabetes deaths. Death rates from diabetes were disproportionately high in the other ethnic groups, especially those with African or Native American ancestry.
::Neel提出他的节食基因假设,不是基于对节食基因的遗传证据,而是为了可能解答为什么似乎提倡糖尿病的基因没有被自然地从某些人口中挑选出来这一谜题。 谜题来源于以下观察,即某些人口——例如南太平洋岛民、撒哈拉以南非洲人和西南土著美国人——在放弃传统饮食和采纳西方饮食后,患肥胖症和糖尿病的人数过多,这反映在2005年美国人口中糖尿病死亡率上,如图所示,美国人口中最大的单一群体是“白人”群体,但糖尿病死亡人数是第二低的,其他族裔群体,特别是非洲或美洲原住民的糖尿病死亡率特别高。This graph shows U.S. death rates from diabetes for 2005. The group that made up the smallest proportion of the population (“Asian/Pacific Islander”) had almost as many diabetes deaths as the group that made up the largest proportion of the population (“whites”).
::这个图显示了美国2005年糖尿病死亡率,这一人口比例最小的群体(“亚洲/太平洋岛民”)的糖尿病死亡率几乎与人口比例最大的群体(“白人”)的糖尿病死亡率相等。Assessing the Thrifty Gene Hypothesis
::评估左翼基因假说One of the assumptions underlying the thrifty gene hypothesis is that human populations that recently developed high rates of obesity and diabetes after Western contact had a long history of recurrent famine. Anthropological evidence contradicts this assumption for at least some of the populations in question. South Pacific Islanders, for example, have long lived in a “land of plenty,” with lush forests year-round on islands surrounded by warm waters full of . Another assumption underlying the thrifty gene hypothesis is that hunter-gatherer people became significantly fatter during periods of plenty. Again, there is little or no evidence that hunter-gatherers traditionally deposited large fat stores when food was readily available.
::大麻基因假设所依据的假设之一是,在西方接触后最近发展出高肥胖率和糖尿病的人类有长期的饥荒历史。 人类学证据与至少部分相关人口的这一假设相矛盾。 比如,南太平洋岛民长期生活在一个“富饶的土地上 ” , 年复一年,在充满温暖水域的岛屿上充满了鲜红的森林。 油质基因假设的另一个假设是猎人-采集者在富足的时期变得脂肪大得多。 再一次,很少有或根本没有证据表明猎人-采集者传统上在食物容易获得时会存放大宗脂肪仓库。Some geneticists have searched directly for so-called thrifty genes. Studies have revealed many genes with small effects associated with obesity or diabetes. However, these genes can explain only a few percentage points of the total population variation in obesity or diabetes.
::一些遗传学家直接搜索了所谓的节食基因。 研究表明了许多与肥胖或糖尿病有关影响较小的基因。 然而,这些基因只能解释肥胖或糖尿病占总人口差异的几个百分点。The Drifty Gene and Other Hypotheses
::挥发的基因和其他假说Given the lack of evidence for the thrifty gene hypothesis, several researchers have suggested alternative hypotheses to explain population variation in obesity and diabetes. One hypothesis posits that susceptibility to obesity and diabetes may be a side effect of heat adaptation . According to this idea, some populations evolved lower metabolic rates as an adaptation to heat stress, because lower metabolic rates reduced the amount of heat that the body produced. The lower metabolic rates also predisposed people to gain excess weight and develop obesity and diabetes.
::由于缺乏关于节食基因假设的证据,一些研究人员提出了解释肥胖和糖尿病人口差异的替代假设。 一种假设认为,易患肥胖和糖尿病可能是热适应的副作用。 根据这一想法,一些人群在适应热应激反应方面出现了低代谢率,因为低代谢率降低了身体产生的热量。 低代谢率还诱使人们增加超重,发展肥胖和糖尿病。A thrifty phenotype hypothesis has also been proposed. This hypothesis suggests that individuals who have inadequate nutrition during fetal might develop an insulin-resistant phenotype. The insulin-resistant phenotype would supposedly prepare these individuals for a life of famine, based on the environment within the womb. In a famine-free environment, however, the thrifty phenotype would lead to the development of diabetes.
::也有人提议了一个精密的苯型假说,这一假说表明胎儿营养不足的人可能会发展一种抗胰岛素的抗胰岛素型。 抗胰岛素型的苯型可以让这些人在子宫环境的基础上过上饥荒的生活。 但是,在没有饥荒的环境中,节食型的苯型会导致糖尿病的发作。The most recent alternative to the thrifty gene hypothesis is the drifty gene hypothesis, which was proposed by biologist John Speakman. He argues that genes protecting humans from obesity were under strong natural selection pressure for a very long period of time while human ancestors were subject to the risk of . According to this view, being able to outrun predators would have been an important factor selecting against fatness. When the risk of predation was lessened — perhaps as early as two million years ago — genes keeping fatness in check would no longer be selected for. Without selective pressure for these genes, their frequencies could change randomly due to . In some populations, by chance, frequencies of the genes could decrease to relatively low levels, whereas in other populations the frequencies could be much higher.
::保护人类免于肥胖的基因在很长一段时间里受到强烈的自然选择压力,而人类祖先则面临这种风险。 根据这一观点,能够战胜掠食动物是选择脂肪的重要选择因素。当先发制人的风险降低 — — 可能早在两百万年前 — — 基因控制脂肪的风险降低时,这些基因将不再被选中。如果没有这些基因的选择性压力,这些基因的频率可能随机而改变。 在一些人群中,基因的频率可能降低到相对较低的水平,而在其他人群中,频率可能更高。Feature: Myth vs. Reality
::特征:神话对现实Myth: Lactose intolerance is an to milk.
::传说:乳糖不耐受是奶的产物。Reality: Lactose intolerance is not an allergy because it is not an immune system response. I t is a sensitivity to milk caused by lactase deficiency so the sugar in milk cannot be digested. Milk allergy does exist, but it is a different condition that occurs in only about four percent of people. It results when milk proteins (not milk sugar) trigger an immune reaction. How can you determine whether you have lactose intolerance or milk allergy? If you can drink lactose-free milk without symptoms, it is likely that you are lactose intolerant and not allergic to milk. However, if lactose-free milk also produces symptoms, it is likely that you have milk allergy. Note that it is possible to have both conditions.
::现实: 乳糖不耐性不是过敏症, 因为它不是免疫系统反应。 乳糖缺乏对牛奶的敏感性, 所以乳糖不能消化。 乳糖过敏确实存在, 但只有大约4%的人有不同的情况。 当乳蛋白( 不是奶糖)引发免疫反应时, 它会产生不同的情况。 您如何确定您是否患有乳糖不耐性或乳脂过敏? 如果您可以喝无乳糖牛奶而没有症状, 您很可能对乳糖不耐性, 对乳糖不过敏。 但是, 如果无乳糖的牛奶也会产生症状, 您很可能患有乳糖过敏。 请注意, 这两种情况都有可能存在 。Myth: If you are lactose intolerant, you will never be able to drink milk or consume other dairy products without suffering adverse physical symptoms.
::传说:如果你乳糖不耐受,你永远无法在没有不良身体症状的情况下喝牛奶或消费其他奶制品。Reality: Lactose intolerance does not mean that consuming milk and other dairy products is out of the question. Besides lactose-free milk, which is widely available, many dairy products have relatively low levels of lactose, so you may be able to consume at least small amounts of them without discomfort. Y ou may be able to consume milk in the form of yogurt without any problems because the bacteria in yogurt produce lactase that breaks down the lactose. Greek yogurt may be your best bet, because it is lower in lactose to begin with. Aged cheeses also tend to have relatively low levels of lactose, because of the cheese-making process. Finally, by gradually adding milk or milk products to your diet, you may be able to increase your tolerance to lactose.
::现实:乳糖不耐症并不意味着消费牛奶和其他奶制品是不可能的。除了广泛供应的无乳糖牛奶之外,许多奶制品的乳糖含量相对较低,因此,你可以在不不舒服的情况下至少消费少量乳糖,这样你就可以在没有任何问题的情况下以酸奶的形式消费牛奶,因为酸奶中的细菌会产生解乳糖的乳酶。希腊酸奶可能是你最好的赌注,因为从乳糖开始,乳糖含量较低。由于乳糖生产过程的缘故,老乳酪的乳糖含量也往往相对较低。最后,通过在饮食中逐渐增加牛奶或奶制品,你也许能够增加对乳糖的耐性。Summary
::摘要-
Milk contains the sugar lactose, a disaccharide. Lactose must be broken down into its two component sugars to be absorbed by the small intestine, and the enzyme lactase is needed for this process.
::牛奶中含有糖乳糖,一种分酸。 乳糖必须分解成其两个组成部分的糖,由小肠吸收,为此需要酶乳糖酶。 -
In about 60 percent of people worldwide, the ability to synthesize lactase and digest lactose declines after the first two years of life. These people become lactose intolerant and cannot consume much milk without suffering symptoms
of
bloating, cramps, and diarrhea.
::在世界上大约60%的人中,合成乳酶和消化乳糖的能力在生命的头两年后下降。 这些人变得不耐乳糖,不能在不出现浮肿、抽搐和腹泻症状的情况下消费大量牛奶。 -
In populations that herded milking animals for thousands of years, lactase persistence evolved. People who were able to synthesize lactase and digest lactose throughout life were strongly favored by natural selection. People — including
many Europeans and European-Americans —
who descended from these early herders generally still have lactase persistence.
::在牧养数千年的哺乳动物人口中,乳腺持久性不断演变,能够合成乳酶和消化乳糖的人一生都受到自然选择的强烈青睐,包括许多欧洲人和欧裔美国人在内的从这些早期牧民中生下来的人一般仍然有乳腺持久性。 -
Human populations may vary in how efficiently they use calories in food. Some people (especially South Pacific Islanders, Native Americans, and sub-Saharan Africans) seem to be able to get by on fewer calories than would be adequate for others, so they tend to easily gain weight, become obese, and develop diseases such as diabetes.
::人类在食物中使用卡路里的效率可能各不相同。 一些人(特别是南太平洋岛民、美洲原住民和撒哈拉以南非洲人)似乎能够用比其他人足够的更少的卡路里过活,因此他们往往容易增加体重、肥胖和患糖尿病等疾病。 -
The thrifty gene hypothesis answers the question of how genes for this ability could have evolved. It proposes that “thrifty genes” were selected for because they allowed people to use calories efficiently and store body fat when food was plentiful so they had a reserve to use when food was scarce. Thrifty genes become detrimental and lead to obesity and diabetes when food is plentiful all of the time.
::精疲力尽的基因假设回答了如何发展这种能力的基因的问题。 它建议选择“极端基因 ” , 因为他们允许人们高效使用卡路里,并在食物充足时储存身体脂肪,从而在食物稀缺时有储备使用。 疲软基因会变得有害,导致肥胖和糖尿病,当食物充足时。 -
Several assumptions underlying the thrifty gene hypothesis have been called into question, and genetic research has been unable to actually identify thrifty genes. Alternate hypotheses to the thrifty gene hypothesis have been proposed, including the drifty gene hypothesis. The latter hypothesis explains variation in the tendency to become obese by genetic drift on neutral genes.
::自由基因假设背后的几种假设受到质疑,基因研究无法实际确定自由基因。 已经提出了对自由基因假设的替代假设,包括流基因假设。 后一种假设解释了中性基因遗传漂移导致肥胖趋势的变化。
Review
::回顾1. Distinguish between the terms lactose and lactase.
::1. 区分乳糖和乳酶这两个术语。2. What is lactose intolerance, and what percentage of all people have it?
::2. 乳糖不容忍是什么,占总人口的百分比是多少?3. Where and why did lactase persistence evolve?
::3. 乳酶持久性在何地和为何演变?4. What is the thrifty gene hypothesis?
::4. 什么是节食基因假设?5. How well is the thrifty gene hypothesis supported by evidence?
::5. 证据对节食基因假设的支持有多好?6. Describe an alternative hypothesis to the thrifty gene hypothesis.
::6. 描述一种替代节食基因假设的假设。7. Do you think that a lack of exposure to dairy products might affect a person’s lactase level? Why or why not?
::7. 你是否认为没有接触乳制品会影响一个人的乳腺水平?为什么或为什么没有?8. Describe an experiment you would want to do or data you would want to analyze that would help to test the thrifty phenotype hypothesis. Remember, you are studying people, so be sure it is ethical! D iscuss possible confounding factors that you should control for, or that might affect the interpretation of your results.
::8. 描述您想要做的实验或您想要分析的数据,以便帮助测试节欲苯型假说。记住,您正在研究人,所以要确信这是合乎道德的!讨论您应该控制的、或可能影响对结果解释的可能混乱因素。9. Explain the relationship between insulin, blood glucose, and type II diabetes.
::9. 解释胰岛素、血糖和第二类糖尿病之间的关系。10. True or False: Lactose persistence evolved more recently than lactose intolerance.
::10. 真实或假:乳糖持久性的演变比乳糖不耐受性更近。11. True or False: The drifty gene hypothesis is dependent on the assumption that fatter people cannot run as effectively as thinner people.
::11. 真实或假:漂流基因假设取决于这样一种假设,即变胖的人无法像瘦小的人一样有效地运行。12. What two ethnic groups in the U.S. have a particularly high rate of death from diabetes? What other type of data would you want to observe to determine whether certain ethnic groups are more susceptible to diabetes? Explain why this additional data would be helpful.
::12. 美国哪些两个族裔群体的糖尿病死亡率特别高?你想观察哪些其他类型的数据来确定某些族裔群体是否更容易患糖尿病?解释为什么这一补充数据会有所帮助。Explore More
::探索更多Does obesity lead to diabetes, or could it be the other way around? Hear a provocative answer to this question in this moving TED talk:
::肥胖是否会导致糖尿病,或者可能是相反的。 在这场充满动人的TED演讲中听到对这一问题的挑衅性回答:Learn more about lactose intolerance here:
::更多了解乳糖不容性: -
Milk contains the sugar lactose, a disaccharide. Lactose must be broken down into its two component sugars to be absorbed by the small intestine, and the enzyme lactase is needed for this process.
