想要男孩？吃早饭吧

想要男孩？吃早饭吧

by Elsa Youngsteadt on April 23, 2008 12:00 AM

作者：Elsa Youngsteadt  2008年4月23日

Moms have more clout than they realize when it comes to the sex of their children. A new study of British mothers suggests that women who eat more--especially more breakfast cereal--at the time of conception are more likely to have boys.

妈妈对胎儿性别的影响比人们想想的要高。一项对英国妈妈母亲的新研究表明，怀孕阶段吃得多，尤其是早饭，很可能会生男孩。

Births of boys are on the decline in several industrialized countries, including the United States, the U.K., and Canada. In the U.S., the proportion of male babies has dropped by about 0.1% since 1970--a small but detectable decline that's amounted to more than 38,000 "missing" boys. The cause of the change is unknown, and some researchers have blamed environmental contaminants that might interfere with hormone balance or poison male embryos. But biologist Fiona Mathews of the University of Exeter in the U.K. wondered if there might be a less sinister force at work.

好几个发达国家，包括美国、英国和加拿，男孩的出生率都在下降。 自1970年以来美国男婴的比例下降了约0.1％，相当于超过38,000人。 人们并不知道导致这一变化的原因，一些研究人员认为环境污染物可能会干扰激素荷尔蒙平衡或对男性胚胎有毒。 但英国埃克塞特大学的生物学家菲奥娜马修斯有不同的看法。

In 1973, biologist Robert Trivers and mathematician Dan Willard predicted that to maximize the number of her descendents, a mother should have some control over the sex of her offspring. If she's healthy and has plenty of food, male offspring are her best investment because they can produce more progeny than can females. But a mediocre male cannot, so mothers with limited resources are better off having girls.

1973年，生物学家罗伯特特里弗斯和数学家丹威拉德预测，为了使后代的数量最大，雌性应该有一些方法来控制其后代的性别。强壮的雄性比平庸的雄性能够产生更多的后代，因此，如果她们身体健康并且有充足的食物，雄性后代是最佳选择，反之，雌性更好一点。

If human moms fit the Trivers-Willard prediction, Mathews and her colleagues expected that women with a greater total calorie intake should produce more boys. The team studied a random sample of 721 pregnant women from southern England who were expecting for the first time and didn't know the sex of their fetuses. Each woman answered a detailed survey about what she had been eating at the time of conception, and the researchers divided the women into three categories based on total calorie intake. In the highest-calorie group, 56% of the women had sons, compared to only 45% in the lowest-calorie group. Much of the effect seemed to depend on whether a woman ate breakfast or not. As the team reports online this week in the Proceedings of the Royal Society B, 59% of moms who ate at least one bowl of cereal per day had boys, compared to only 43% of women who ate less than one bowl per week. With fewer women eating breakfast, Mathews says that the Trivers-Willard effect could be at least part of the explanation for dropping sex ratios. Breakfast may be particularly important for maintaining blood sugar levels, which have been linked to increased production of males in other mammals, although the precise mechanism is unknown (ScienceNOW, 30 November 2007).

马修斯和她的同事们认为，如果特里弗斯--威拉德预测也适用于人类，那么我们可以预期妇女摄入总热量较大应该生更多的男孩。 该小组通过随机抽样，对英格兰南部721位首次怀孕且胎儿性别未知的的孕妇进行了调查。每个孕妇都详细回答了怀孕时的热量摄入量，根据的摄入热量的不同，她们可以划分为三类：在最高热量组，生男孩的比例是56％，而最低热量组只有45％。 造成差别的原因似乎取决于她们有没有吃早饭。正如他们在皇家学会研究进展上报道的那样，59%每天至少吃一碗麦片的孕妇生的是男孩，而那些每周吃不到一碗的则生男孩的比例是43%。马修斯说，随着吃早餐的妇女变少，特里弗斯--威拉德效应能至少性别比例部分的解释下降。早餐可能是对维持血糖水平特别重要，虽然确切的机制尚不清楚，但在其他哺乳动物中高血糖水平与高比例的雄性胎儿相关。

Elissa Cameron, a mammal ecologist at the University of Pretoria in South Africa, says the results are convincing and important as the first evidence for the Trivers-Willard hypothesis in modern humans. But it's not clear whether nutrition is the driving force behind the declining number of boys, says Shanna Swan, an epidemiologist at the University of Rochester School of Medicine and Dentistry in New York. She says that if maternal diet is a factor, "it's undoubtedly not the only one," and environmental contaminants could still be part of the story.

南非的比勒陀利亚大学的哺乳动物生态学家埃利萨卡梅 伦说，做为特里弗斯--威拉德假说效应在现代人上的第一个证据，该结果是令人信服。但在纽约罗切斯特学院医学和牙科学的流行病学家Shanna Swan认为目前尚不清楚营养是否是男生人数下降原因。 她说，如果孕妇饮食是一个因素，那绝不是唯一的，还要包括环境污染物。