健康指南:母乳餵養的孩子智商更高

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.

新近一項研究得出結論稱，延長母乳餵養期可使孩子更加聰明。該研究發表於美國醫學會(American Medical Association)主辦的《美國醫學會雜誌•兒科學》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.

就許多方面而言，這項研究並不會讓母乳餵養的提倡者感到意外，他們在很早之前就提出母乳餵養與認知能力之間存在關聯，現在他們只不過是又多了一項支持他們論點的研究。對於那些持懷疑態度的人，他們則可能會堅持認爲最重要的是嬰兒母親的智商，或是認爲針對母乳餵養的社會壓力會導致家長不堪重負，而這本身會給孩子的發育帶來麻煩。然而，目前這些研究發現可能會給公共健康倡議者推動提高母乳餵養比例的行動提供強有力的支持。美國疾病控制與預防中心(Centers for Disease Control and Prevention)的數據顯示，母乳餵養的比例在嬰兒出生伊始爲75%左右，但在嬰兒一週歲時便降低至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.

這項發表在JAMA的研究並不是最早將母乳餵養與智商水平聯繫在一起的研究，但研究人員稱它的實驗樣本大，而且它還排除了嬰兒母親的智商及孩子接受的教育等變量，因此更加讓人信服。該研究的第一作者、哈佛醫學院(Harvard Medical School)的兒科學助理教授曼迪•貝爾福特(Mandy Belfort)指出，以往的研究在對可能影響孩子智商的其他因素進行調整方面存在問題，而且它們的實驗樣本較小，或是未考慮到母乳餵養期的時間長短。

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.

新近這項研究根據他們可接觸多少書籍等因素調查了每個孩子的生活環境，並對每個孩子的母親進行了智商測試。他們還針對可能影響智商的因素提出了詳細的問題，比如兒童保育、家庭收入及父母的教育程度等，然後利用統計模型剔除這些因素。貝爾福特稱，她希望他們得出的是母乳餵養與智商之間的真實聯繫。

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，母乳餵養很難通過隨機性的實驗進行研究，因爲把一部分孩子分在非母乳餵養組是不道德的行爲，所以研究人員只能選擇像她所展開的那種觀察性研究。從1999年至2010年期間，波士頓兒童醫院的研究人員對1,312名嬰兒及他們的母親進行了跟蹤研究。他們要找出其中有多少孩子在一週歲時依然在吃母乳，然後分別在這些孩子三歲和七歲時對他們進行智商測試。

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.

智商是天分與後天培養的奇特混合物，排除其中一個因素頗具難度。母乳餵養首先與社會階層和財富存在很大關係，其中生活更富庶、教育程度更高的女性通常會選擇盡力以母乳餵養孩子。

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.

那些在一週歲後依然吃母乳的孩子，他們在三歲時的語言理解能力測試中得分更高，這表示他們對所聽到的話的理解能力要高於喝配方奶的同齡人。到七歲時，母乳餵養的孩子在口頭及非口頭智商測試中的得分也更高。

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.

在三歲大的孩子中，每個月的母乳餵養可使他們的認知能力分數平均提高0.21分。在七歲大的孩子中，每個月的母乳餵養可使他們的口頭及非口頭智商測試的得分分別提高0.35分和0.29分。貝爾福特稱，一整年的母乳餵養可使孩子的智商分值比非母乳餵養的孩子高出四分左右，考慮到智商的平均分值大約爲100分，這算得上一個大幅提升。這只是針對在飲食中會吃些母乳的孩子而言，那些在大約六個月大、開始食用固體食物之前只吃母乳的孩子具有更大的智商優勢。

'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.

貝爾福特說：“對於個人而言，我們難以分辨出兩三分的智商差距，但它對整個社會而言非常重要。如果我們能提升智商水平，那麼我們就不必向智商較低人羣投入那麼多資源。”這意味着，隨着智商的整體提高，我們可以減少對補償教育項目的資金投入。

Dr. Amy Tuteur, an obstetrician who writes a blog called , 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•圖特(Amy Tuteur)博士卻沒有被母乳餵養可使智商提高四分的結論說服，她是一名產科醫生及博客的博主。她說，若要證明那並不只是隨機變量，智商提升值還需更高些。她指出：“智商水平涉及多個方面，我對認爲任意一件事就能馬上使智商發生重大改觀的觀點持懷疑態度。美國民衆的智商一直在穩步提高，它在母乳餵養率上升時有提高，在母乳餵養率下降時也有提高。”

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.

母乳與大腦發育之間的潛在關聯只是剛開始得到梳理。有些觀點提出，促成智商提升的並非母乳中的成分，而是母乳餵養過程中母親與孩子之間產生的情感紐帶。其他一些觀點則把它歸功於在母乳中發現的DHA和ARA等營養成分，這些脂肪酸都與大腦發育有關。一些配方奶廠家也在它們的產品中添加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.

西雅圖兒童醫院研究中心的兒科醫生迪米特里•克里斯塔基斯(Dimitri Christakis)稱：“母乳中有一些確實在其他物質中找不到的營養成分，我們也不完全瞭解其中的原因。”他並未參與發表於JAMA的那項研究。

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《美國醫學會雜誌•兒科學》上就該項研究撰寫了一篇評論，他也是一個名爲“母乳餵養全球倡議”(Global Breast-feeding Initiative)的倡導組織的領導者。他在評論中提出，該項研究有望平息對母乳餵養最有益於大腦發育的質疑，社會應當爲母親母乳餵養創造更輕鬆和更舒適的環境。

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.

對於住在加州千橡市的阿姆拉•查德利-尼爾(Amra Chudleigh-Neal)而言，提高智商只是她以母乳餵養其六週大的女兒的原因之一。她說，她七歲大的大女兒的智商高於平均水平，她認爲這在一定程度上是因爲她在女兒六個月大之前只給她餵母乳。

'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.

她說：“以母乳餵養這第二個孩子似乎是做出了一些犧牲，你會想‘哦，我的天，這真的值得嗎’，但是回想一下我的大女兒，我就會認爲這確實有關係。”查德利-尼爾受到了The Pump Station的廣泛幫助，這家位於洛杉磯地區的母乳餵養資源中心爲媽媽們提供各種幫助，比如幫她們聯繫哺乳問題專業人士。

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，並非每個人都能成功做到母乳餵養，家長們也不必爲此擔心。貝爾福特建議：“你可以和孩子說說話，抱着他，讀書給他聽，孩子的發育涉及許許多多不同的因素。”

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.

研究母乳餵養問題的一個難處是，每次餵奶都會因爲母親的狀況及其飲食而有所變動。因此，波士頓兒童醫院的研究人員也調查了媽媽們的飲食中一個可能會影響孩子大腦發育的成分──富含DHA的魚。

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.

那些研究人員發現，每週吃魚兩次以上或更多次似乎有益於智商，但這給兒童認知能力帶來的提升在統計數據上並無顯著差異。