Breast-feeding longer can make children smarter. That's the conclusion of a study published Monday in JAMA Pediatrics, a journal of the American Medical Association.
新近一项研究得出结论称，延长母乳喂养期可使孩子更加聪明。该研究发表于美国医学会(American Medical Association)主办的《美国医学会杂志•儿科学》上(JAMA Pediatrics)。
In many ways, the study won't surprise proponents of breast-feeding, who have long posited a connection between nursing and cognition and now have an additional piece of research to back up their argument. Skeptics could likely stick to the view that what matters most is how smart a baby's mom is, or that social pressure to breast-feed can have its own problems for children's development by creating stressed-out parents. However, the findings are likely to add muscle to public-health advocates' push to increase breast-feeding rates, which start out around 75% but slump to an average of 25% at a baby's first birthday, according to the Centers for Disease Control and Prevention.
就许多方面而言，这项研究并不会让母乳喂养的提倡者感到意外，他们在很早之前就提出母乳喂养与认知能力之间存在关联，现在他们只不过是又多了一项支持他们论点的研究。对于那些持怀疑态度的人，他们则可能会坚持认为最重要的是婴儿母亲的智商，或是认为针对母乳喂养的社会压力会导致家长不堪重负，而这本身会给孩子的发育带来麻烦。然而，目前这些研究发现可能会给公共健康倡议者推动提高母乳喂养比例的行动提供强有力的支持。美国疾病控制与预防中心(Centers for Disease Control and Prevention)的数据显示，母乳喂养的比例在婴儿出生伊始为75%左右，但在婴儿一周岁时便降低至25%的平均水平。
The JAMA study isn't the first to study a link between nursing and intelligence, but researchers say it is more conclusive because of its size and how it has isolated variables such as the mother's IQ and the child's upbringing. Previous studies have had difficulty adjusting for other factors that might influence a child's IQ, were limited by their small size or didn't account for length of nursing, said Mandy Belfort, the JAMA study's lead author and assistant professor of pediatrics at Harvard Medical School.
这项发表在JAMA的研究并不是最早将母乳喂养与智商水平联系在一起的研究，但研究人员称它的实验样本大，而且它还排除了婴儿母亲的智商及孩子接受的教育等变量，因此更加让人信服。该研究的第一作者、哈佛医学院(Harvard Medical School)的儿科学助理教授曼迪•贝尔福特(Mandy Belfort)指出，以往的研究在对可能影响孩子智商的其他因素进行调整方面存在问题，而且它们的实验样本较小，或是未考虑到母乳喂养期的时间长短。
The latest study examined and rated each child's environment based on factors such as how many books are available, and gave each mother an IQ test. They also asked detailed questions about factors that might influence IQ, such as child care, income and parental education. They then subtracted those factors using a statistical model. Dr. Belfort said she hopes that 'what we have left is the true connection' with nursing and IQ.
新近这项研究根据他们可接触多少书籍等因素调查了每个孩子的生活环境，并对每个孩子的母亲进行了智商测试。他们还针对可能影响智商的因素提出了详细的问题，比如儿童保育、家庭收入及父母的教育程度等，然后利用统计模型剔除这些因素。贝尔福特称，她希望他们得出的是母乳喂养与智商之间的真实联系。
Breast-feeding is hard to study in a randomized trial because it is unethical to put some children in the non- group, Dr. Belfort said, which leaves researchers with observational studies such as the one she conducted. Researchers at Boston Children's hospital followed 1,312 babies and mothers from 1999 to 2010. They found out how many of those children were still consuming their mothers' milk at their first birthday, and then tested the children's intelligence at ages 3 and 7.
她指出，母乳喂养很难通过随机性的实验进行研究，因为把一部分孩子分在非母乳喂养组是不道德的行为，所以研究人员只能选择像她所展开的那种观察性研究。从1999年至2010年期间，波士顿儿童医院的研究人员对1,312名婴儿及他们的母亲进行了跟踪研究。他们要找出其中有多少孩子在一周岁时依然在吃母乳，然后分别在这些孩子三岁和七岁时对他们进行智商测试。
Intelligence is a strange brew of nature and nurture and isolating one factor is challenging. Breast-feeding in the first place has a lot to do with class and wealth, with richer, better educated women typically opting to make the effort to nurse their babies.
智商是天分与后天培养的奇特混合物，排除其中一个因素颇具难度。母乳喂养首先与社会阶层和财富存在很大关系，其中生活更富庶、教育程度更高的女性通常会选择尽力以母乳喂养孩子。
Children who were still nursing after a year had higher receptive language scores at age 3, which means they understood what was being said to them better than their formula-fed peers. At age 7, the breast-fed children scored higher on verbal and nonverbal intelligence tests.
那些在一周岁后依然吃母乳的孩子，他们在三岁时的语言理解能力测试中得分更高，这表示他们对所听到的话的理解能力要高于喝配方奶的同龄人。到七岁时，母乳喂养的孩子在口头及非口头智商测试中的得分也更高。
In 3 year olds, every month of breast-feeding raised cognition scores by an average of .21 point. Each month of breast-feeding was associated with a .35 more verbal IQ point and a .29 more nonverbal point in the 7 year olds. A full year of nursing would boost a child's IQ by about 4 points over a child who didn't nurse, said Dr. Belfort, a significant bump considering that IQs average around 100. That is for children getting some breast milk in their diets; those consuming only breast milk before starting to eat solid foods around six months of age saw even greater advantages.
在三岁大的孩子中，每个月的母乳喂养可使他们的认知能力分数平均提高0.21分。在七岁大的孩子中，每个月的母乳喂养可使他们的口头及非口头智商测试的得分分别提高0.35分和0.29分。贝尔福特称，一整年的母乳喂养可使孩子的智商分值比非母乳喂养的孩子高出四分左右，考虑到智商的平均分值大约为100分，这算得上一个大幅提升。这只是针对在饮食中会吃些母乳的孩子而言，那些在大约六个月大、开始食用固体食物之前只吃母乳的孩子具有更大的智商优势。
'For an individual person, it would be hard to tell a two or three point difference in IQ, but it would matter a lot for society,' said Dr. Belfort. 'If we can shift the IQ up, we would have to invest less resources at the low end.' Meaning that with improved IQ scores across the board, less funding would have to be spent on remedial education programs.
贝尔福特说：“对于个人而言，我们难以分辨出两三分的智商差距，但它对整个社会而言非常重要。如果我们能提升智商水平，那么我们就不必向智商较低人群投入那么多资源。”这意味着，随着智商的整体提高，我们可以减少对补偿教育项目的资金投入。
Dr. Amy Tuteur, an obstetrician who writes a blog called skepticalob.com, is unconvinced by a four-point increase in IQ, saying the bump needs to be bigger to prove that it isn't just random variation. 'Intelligence is multifactoral and the idea that any one thing can make a big difference right away makes me skeptical,' she said. 'American IQ has been increasing steadily, it rose when breast-feeding rates were going down and it rose when breast-feeding rates were going up.'
然而，埃米•图特(Amy Tuteur)博士却没有被母乳喂养可使智商提高四分的结论说服，她是一名产科医生及博客skepticalob.com的博主。她说，若要证明那并不只是随机变量，智商提升值还需更高些。她指出：“智商水平涉及多个方面，我对认为任意一件事就能马上使智商发生重大改观的观点持怀疑态度。美国民众的智商一直在稳步提高，它在母乳喂养率上升时有提高，在母乳喂养率下降时也有提高。”
The possible link between breast milk and brain development is only starting to be teased out. Some theories suggest that it isn't the content of the milk but the bond between mother and child developed while nursing that accounts for some of the boost. Other ideas hinge on nutrients found in breast milk such as DHA and ARA, which are fatty acids linked to brain development. Some formula companies put DHA and ARA in their offerings.
母乳与大脑发育之间的潜在关联只是刚开始得到梳理。有些观点提出，促成智商提升的并非母乳中的成分，而是母乳喂养过程中母亲与孩子之间产生的情感纽带。其他一些观点则把它归功于在母乳中发现的DHA和ARA等营养成分，这些脂肪酸都与大脑发育有关。一些配方奶厂家也在它们的产品中添加DHA和ARA。
'There are nutrients in breast milk that don't really exist anywhere else, and we don't fully know why,' says Dimitri Christakis, a pediatrician at Seattle Children's Hospital Research Institute and wasn't involved in the research.
西雅图儿童医院研究中心的儿科医生迪米特里•克里斯塔基斯(Dimitri Christakis)称：“母乳中有一些确实在其他物质中找不到的营养成分，我们也不完全了解其中的原因。”他并未参与发表于JAMA的那项研究。
He wrote an editorial in JAMA pediatrics on the study and leads an advocacy group called the Global Breast-feeding Initiative. In the editorial he contends the JAMA study should put skepticism to rest about whether breast-feeding is best for brain development and that society should make it easier and more acceptable for moms to nurse.
克里斯塔基斯在《美国医学会杂志•儿科学》上就该项研究撰写了一篇评论，他也是一个名为“母乳喂养全球倡议”(Global Breast-feeding Initiative)的倡导组织的领导者。他在评论中提出，该项研究有望平息对母乳喂养最有益于大脑发育的质疑，社会应当为母亲母乳喂养创造更轻松和更舒适的环境。
For Amra Chudleigh-Neal of Thousand Oaks, Calif., intelligence is just one more reason for her to breast-feed her 6-week old daughter. She said her older child, now 7, has above average IQ, which Ms. Chudleigh-Neal said could be in part because she exclusively breast-fed until her daughter was 6- months old.
对于住在加州千橡市的阿姆拉•查德利-尼尔(Amra Chudleigh-Neal)而言，提高智商只是她以母乳喂养其六周大的女儿的原因之一。她说，她七岁大的大女儿的智商高于平均水平，她认为这在一定程度上是因为她在女儿六个月大之前只给她喂母乳。
'It tends to be a little more of a sacrifice to nurse the second child, you think 'oh my gosh is it really worth it' but looking back with my older child I believe it did make a difference,' she said. Ms. Chudleigh-Neal receives extensive support from The Pump Station, a Los Angeles-area nursing resource center that helps with things like connecting moms to lactation professionals.
她说：“以母乳喂养这第二个孩子似乎是做出了一些牺牲，你会想‘哦，我的天，这真的值得吗’，但是回想一下我的大女儿，我就会认为这确实有关系。”查德利-尼尔受到了The Pump Station的广泛帮助，这家位于洛杉矶地区的母乳喂养资源中心为妈妈们提供各种帮助，比如帮她们联系哺乳问题专业人士。
Not everyone can breast-feed successfully, and that needn't make parents worry. 'Talk to your baby, hold your baby and read to your baby,' Dr. Belfort said. 'There are so many different factors in a child's development.'
然而，并非每个人都能成功做到母乳喂养，家长们也不必为此担心。贝尔福特建议：“你可以和孩子说说话，抱着他，读书给他听，孩子的发育涉及许许多多不同的因素。”
One difficulty in studying breast milk is that every feeding can vary based on the mother and what she has eaten. So the Boston researchers also examined a component in mothers' diets that might be responsible for children's brain development: fish, which contains DHA.
研究母乳喂养问题的一个难处是，每次喂奶都会因为母亲的状况及其饮食而有所变动。因此，波士顿儿童医院的研究人员也调查了妈妈们的饮食中一个可能会影响孩子大脑发育的成分──富含DHA的鱼。
The authors found that more than two or more servings of fish per week seemed to confer IQ benefits, but that boost in children's cognition wasn't statistically significant.
那些研究人员发现，每周吃鱼两次以上或更多次似乎有益于智商，但这给儿童认知能力带来的提升在统计数据上并无显著差异。