An extended duration of breastfeeding of up to two years is encouraged by many health authorities, but information regarding the composition of milk after one year postpartum is limited. The goal of this study was to determine the association between the duration of lactation and macronutrient contents, immunoglobulin A (IgA) levels and total antioxidant capacity (TAC) in human milk (HM), from 1 to 24 months postpartum. Cross-sectional milk samples were collected between January and April 2019 from mothers with healthy full-term children who had been lactating for 1 to 24 months. The HM was biochemically analyzed for protein and carbohydrate contents by colorimetric assays. The fat content was determined by capillary centrifugation, and the energy content was calculated from the results of centrifugation assays. IgA levels and TAC were determined by ELISA and a Trolox equivalent antioxidant capacity (TEAC) assay, respectively. Pearson’s correlation coefficient and Spearman’s rank correlation coefficient were used to determine associations between months of lactation and milk composition, and multiple regression analysis was used to assess associations between months of lactation and milk composition adjusted for relevant covariates. Differences were considered significant at p < 0.05. One hundred eighty-four milk samples were analyzed. The month of lactation was positively associated with the fat concentration (B = 0.31, SE = 0.09, p = 0.001), energy content (B = 3.11, SE = 0.92, p = 0.001), and IgA (B = 4.17, SE = 1.08, p < 0.001) but negatively associated with the carbohydrate concentration (B = − 0.22, SE = 0.01, p = 0.04). No association was observed between the month of lactation and the protein concentration or TAC after adjustment for maternal age, maternal BMI, birth order, and breastfeeding frequency. The duration of lactation was found to be positively associated with the fat, energy, and IgA content in HM for up to two years postpartum, and negatively associated with carbohydrate concentration. More prospective cohort studies are needed to obtain evidence-based knowledge regarding the changes in HM composition throughout the course of lactation.

中文翻译：

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1 至 24 个月母乳的常量营养素、免疫球蛋白 a 和总抗氧化能力概况：泰国的一项横断面研究

许多卫生当局鼓励母乳喂养时间延长至两年，但有关产后一年后母乳成分的信息有限。本研究的目的是确定哺乳期持续时间与大量营养素含量、免疫球蛋白 A (IgA) 水平和人乳 (HM) 中总抗氧化能力 (TAC) 之间的关联，从产后 1 到 24 个月。横断面牛奶样本是在 2019 年 1 月至 4 月期间从哺乳期 1 至 24 个月的健康足月婴儿的母亲那里收集的。通过比色测定法对HM进行生物化学分析以获取蛋白质和碳水化合物含量。脂肪含量通过毛细管离心测定，能量含量由离心测定结果计算。IgA 水平和 TAC 分别通过 ELISA 和 Trolox 等效抗氧化能力 (TEAC) 测定确定。Pearson 相关系数和 Spearman 等级相关系数用于确定泌乳月份与牛奶成分之间的关​​联，多元回归分析用于评估泌乳月份与针对相关协变量调整的牛奶成分之间的关​​联。在 p < 0.05 时，差异被认为是显着的。分析了 184 个牛奶样品。哺乳月份与脂肪浓度 (B = 0.31, SE = 0.09, p = 0.001)、能量含量 (B = 3.11, SE = 0.92, p = 0.001) 和 IgA (B = 4.17, SE = 1.08，p < 0.001）但与碳水化合物浓度呈负相关（B = - 0.22，SE = 0.01，p = 0.04）。在调整母亲年龄、母亲 BMI、出生顺序和母乳喂养频率后，未观察到哺乳月份与蛋白质浓度或 TAC 之间存在关联。泌乳持续时间与产后两年内 HM 中的脂肪、能量和 IgA 含量呈正相关，与碳水化合物浓度呈负相关。需要更多的前瞻性队列研究来获得关于整个哺乳过程中 HM 组成变化的循证知识。并且与碳水化合物浓度呈负相关。需要更多的前瞻性队列研究来获得关于整个哺乳过程中 HM 组成变化的循证知识。并且与碳水化合物浓度呈负相关。需要更多的前瞻性队列研究来获得关于整个哺乳过程中 HM 组成变化的循证知识。