Effects of maternal nutrition and infant gender on breastmilk antibodies and micronutrients

尽管全世界儿童死亡率正在下降，但与家庭收入和婴儿性别有关的儿童死亡率仍然存在差异，特别是在性别歧视和营养不良普遍存在的地方。造成这些差异的一个因素可能是儿童从母亲的母乳中获得的保护水平。这个项目将通过分析母乳样本来测试关于父母投资的进化理论，看看对于有儿子和女儿的母亲来说，母乳的有益含量是否会因母亲的营养状况以及两者的组合而有所不同。这一发现将为现代社会降低弱势儿童死亡率的努力提供参考。该项目将为妇女和少数族裔学生提供接受实验室方法培训和指导的机会，并参与对全球健康有影响的研究。特里弗斯-威拉德假说(TWh)预测，在一夫多妻制的人口中，男性的身体或经济条件决定了他们的适婚能力，父母对女儿和儿子的投入不平等。具体地说，它预测，身体状况良好的母亲将更多地投资于儿子，而状况不佳的母亲将更多地投资于女儿，因为这些策略可能会提高她们的生育成功。之前关于母乳质量性别偏见的研究，特别是牛奶营养水平的研究，报道了好坏参半的结果。这些研究的重点是产生能量的营养素(如脂肪、糖)，而不是牛奶中对婴儿生存和成长不可或缺的其他营养和非营养成分。该项目通过不仅使用母乳能量的测量，而且使用维生素(B9或叶酸)和抗体(分泌型免疫球蛋白A或SIgA)作为母亲投资的指标来检查TWH，从而为这一研究机构做出贡献。来自肯尼亚农村一夫多妻制部落Ariaal部落的220名母亲的母乳样本的横断面随机样本将被分析。由此产生的数据将被用来检验以下预测：1)母亲的营养(如肥胖、微量营养素状况)将积极地预测叶酸/SIgA，2)这种影响将受到婴儿性别的调节，3)营养不良的母亲的乳汁将表现出对女儿的偏好，以及其他母亲的乳汁对男孩的偏爱。这些发现将促进对特定社会文化和生态背景下母乳成分中可能存在的性别偏见的多方面看法。这将有助于我们在智力上理解人类父母投资的条件变异，这对婴儿生长和健康的性别差异具有重要意义。

Although worldwide childhood mortality rates are declining, there continue to be disparities in child mortality related to household income and sex of the infant, particularly in places where gender discrimination and malnutrition are common. One factor that may contribute to these differences is the level of protection that children receive from their mothers' milk. This project will test evolutionary theories about parental investment by analyzing breast milk samples, to see whether the beneficial contents of breast milk differ for mothers of sons versus daughters, by maternal nutritional status, and by a combination of the two. The findings will inform efforts in modern society to reduce the mortality of vulnerable children. The project will provide opportunities for women and minority students to be trained and mentored in laboratory methods and to participate in research with global health implications. The Trivers-Willard hypothesis (TWH) predicts unequal parental investment between daughters and sons in polygynous populations where somatic or economic conditions of males determine their marriageability. Specifically, it predicts that mothers in good condition will invest more in sons while mothers in poor condition will invest more in daughters because these strategies may enhance their reproductive success. Previous studies on sex bias in human milk quality, particularly milk nutrient levels, have reported mixed results. These studies focused on energy-yielding nutrients (e.g. fat, sugar), but not on other nutritive and non-nutritive components of milk that are indispensable for infants to survive and thrive. This project contributes to this body of research by examining the TWH using not only measures of breast milk energy, but also vitamins (B9 or folate) and antibodies (secretory immunoglobulin A or sIgA) as indicators, of maternal investment. A cross-sectional random sample of breast milk specimens from 220 mothers of the Ariaal tribe, a polygynous population of rural Kenya, will be analyzed. The resulting data will be used to test the following predictions: 1) maternal nutrition (e.g. adiposity, micronutrient status) will positively predict folate/sIgA, 2) this effect will be moderated by the sex of the infant, and 3) milk of under-nourished mothers will exhibit preference toward daughters and milk of other mothers toward sons. The findings will facilitate a multi-faceted view on possible sex bias in human milk components in a specific sociocultural and ecological context. This will contribute intellectually to our understanding of conditional variation in human parental investment, which has important implications for sex differences in infant growth and health.