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BackgroundLactoferrin (Lf) is a multifunctional protein and one of the most abundant proteins in human milk. Various factors may affect its concentration in human milk, such as stage of lactation, ethnicity, and diet.ObjectivesThe objectives of the present study were to examine the dynamic change in milk Lf throughout the course of lactation and explore factors associated with milk Lf concentrations in various Chinese populations.MethodsThis investigation was a part of a large cross-sectional study conducted in 11 provinces/autonomous regions/municipalities (Beijing, Gansu, Guangdong, Guangxi, Heilongjiang, Inner Mongolia, Shandong, Shanghai, Xinjiang, Yunnan, and Zhejiang) across China between 2011 and 2013. Lactating women (n = 6481) within 0⁻330 days postpartum were recruited in the original study. A sub-sample of 824 women was randomly selected, and milk Lf concentrations were determined by UPLC/MS.ResultsThe Lf concentration in milk from women delivering at term was 3.16 g/L, 1.73 g/L and 0.90 g/L for colostrum, transitional milk, and mature milk, respectively. Lf concentrations differed significantly between stages of lactation (colostrum vs. transitional milk, colostrum vs. mature milk, transitional milk vs. mature milk, all p < 0.001). Maternal BMI, age, mode of delivery, parturition, protein intake, and serum albumin concentration were not correlated with milk Lf concentration. However, milk Lf concentrations varied among different geographical regions (Guangdong (1.91 g/L) vs. Heilongjiang (1.44 g/L), p = 0.037; Guangdong (1.91 g/L) vs. Gansu (1.43 g/L), p = 0.041) and ethnicities (Dai (1.80 g/L) vs. Tibetan (0.99 g/L), p = 0.007; Han (1.62 g/L) vs. Tibetan (0.99 g/L), p = 0.002) in China.ConclusionsThe concentration of Lf in human milk changes dynamically throughout lactation. Few maternal characteristics affect the milk Lf concentration, but it varies across different geographical regions and ethnicities in China.

Macronutrient contents in human milk are the common basis for estimating these nutrient requirements for both infants and lactating women. A mid‐infrared human milk analyser (HMA, Miris, Sweden) was recently developed for determining macronutrient levels. The purpose of the study is to compare the accuracy and precision of HMA method with fresh milk samples in the field studies with chemical methods with frozen samples in the lab. Full breast milk was collected using electric pumps and fresh milk was analyzed in the field studies using HMA. All human milk samples were thawed and analyzed with chemical reference methods in the lab. The protein, fat and total solid levels were significantly correlated between the two methods and the correlation coefficient was 0.88, 0.93 and 0.78, respectively (p  <  0.001). The mean protein content was significantly lower and the mean fat level was significantly greater when measured using HMA method (1.0 g 100 mL−1 vs 1.2 g 100 mL−1and 3. 7 g 100 mL−1 vs 3.2 g 100 mL−1, respectively, p  <  0.001). Thus, linear recalibration could be used to improve mean estimation for both protein and fat. There was no significant correlation for lactose between the two methods (p  >  0.05). There was no statistically significant difference in the mean total solid concentration (12.2 g 100 mL−1vs 12.3 g 100 mL−1, p  >  0.05). Overall, HMA might be used to analyze macronutrients in fresh human milk with acceptable accuracy and precision after recalibrating fat and protein levels of field samples. [ABSTRACT FROM AUTHOR]