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

虽然全世界的儿童死亡率正在下降，但儿童死亡率仍然存在与家庭收入和婴儿性别有关的差异，特别是在性别歧视和营养不良现象普遍的地方。可能造成这些差异的一个因素是儿童从母乳中获得的保护程度。该项目将通过分析母乳样本来测试有关父母投资的进化理论，以了解母乳中有益的成分是否因母亲的营养状况以及两者的结合而对儿子和女儿的母亲有所不同。研究结果将为现代社会降低弱势儿童死亡率的努力提供信息。该项目将为妇女和少数民族学生提供机会，使其接受实验室方法方面的培训和指导，并参与具有全球卫生影响的研究。Trivers-Willard假说（TWH）预测，在一夫多妻制的人群中，男性的身体或经济条件决定了他们的适婚性，女儿和儿子之间的父母投资不平等。具体而言，它预测，条件好的母亲会在儿子身上投入更多，而条件差的母亲会在女儿身上投入更多，因为这些策略可能会提高她们的生育成功率。以前关于母乳质量，特别是母乳营养水平的性别偏见的研究报告了混合结果。这些研究集中在产生能量的营养素（如脂肪、糖），而不是牛奶中对婴儿生存和茁壮成长必不可少的其他营养和非营养成分。该项目通过不仅使用母乳能量测量，而且还使用维生素（B 9或叶酸）和抗体（分泌型免疫球蛋白A或sIgA）作为母体投资指标来检查TWH，为这一研究体系做出了贡献。将对来自肯尼亚农村一夫多妻制人口Ariaal部落的220名母亲的母乳标本进行横断面随机抽样分析。由此产生的数据将用于检验以下预测：1）母体营养（例如肥胖、微量营养素状态）将积极预测叶酸/sIgA，2）这种影响将受到婴儿性别的调节，3）营养不良母亲的乳汁将表现出对女儿的偏好，而其他母亲的乳汁将表现出对儿子的偏好。这些发现将有助于在特定的社会文化和生态背景下对母乳成分中可能存在的性别偏见进行多方面的研究。这将有助于我们理解人类父母投资的条件变化，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.