A simple system for measuring the level of free fatty acids in human milk collected as dried milk spot

Wax-coated dried-milk-spot paper for human milk protein compositional analysis

Studies exploring human milk are often hindered by laborious and costly conventional sampling, resulting in small sample sizes. Here, we implement a paper-based sampling method, dried milk spots (DMS), as an alternative to increase sampling capacity and frequency, primarily tailored for protein compositional analysis. Uncoated paper was unsuited for DMS, with β-casein recovery at 64 ± 1 % and α-lactalbumin at 85 ± 2 % after storage of 14 days. A bespoke wax-coated paper was thus developed to improve protein recovery, alongside an ethanol pre-wetting step to enhance wicking of milk. Using this ethanol-pre-wetted-wax-coated paper, β-casein recovery increased to 80 ± 6 % and α-lactalbumin to 82 ± 1 %, with the β-casein-to-α-lactalbumin recovery ratio reaching 97 ± 8 % after storage of 14 days. This DMS method requires only room temperature storage, facilitates easy transportation, and supports protein compositional analysis, thus holding promise for future application in human milk studies.

Determination of Free Fatty Acids in Breast Milk Reveals the Presence of Hydroxypalmitic and Stearic Acids

Breast milk is a rich source of fatty acids (FAs) while being irreplaceable for the health and development of an infant. Herein, we present a fast and simple method for the direct detection and quantification of 37 free FAs (FFAs) in breast milk samples, avoiding any derivatization step, and a study on the % variation of FA contents in samples collected from the same mother within five consecutive days. The average breakdown of FAs was 60.5% saturated and 39.5% unsaturated, in which polyunsaturated FAs were 13.3% and monounsaturated FAs 26.2%. The most abundant FFA in the breast milk samples was C12:0 (18.3%), followed by C10:0 (15.0%), suggesting that further attention must be paid to the presence and role of medium-chain FAs. Among unsaturated FAs, oleic acid (C18:1 n-9) (13.3%) and linoleic acid (C18:2 n-6) (10.1%) were the most abundant. Remarkable variations of FFA contents within the five consecutive days were observed for C8:0, C10:0, C12:0, C18:1 n-9, and C18:2 n-6. The two isomers α-linolenic acid (C18:3 n-3) and γ-linolenic acid (C18:3 n-6) were quantified in all breast milk samples. The ratio of γ-linolenic acid, which most recently is important for cardiac metabolic maturation, to α-linolenic acid was found to be 1:2. Most importantly, in the present study, we explored the presence of bioactive saturated monohydroxy fatty acids (SHFAs), demonstrating for the first time the existence of distinct hydroxypalmitic and hydroxystearic acids (HPAs and HSAs, respectively) in breast milk.

Human Milk Lipid Profiles around the World: A Systematic Review and Meta-Analysis

Reported breast milk lipid concentrations may vary with geographical region, postnatal age, and year of sample collection. In this review, we summarized data on the concentrations of total fat, total phospholipids, cholesterol, and fatty acids in human milk worldwide and their variation according to lactation stage, study area, and sample collection year. A systematic literature search was performed using the PubMed, Embase, Web of Science, and Medline databases for English-language papers and Wanfang and China National Knowledge Infrastructure databases for Chinese-language papers. A total of 186 studies evaluating the human milk lipid profiles were included. According to random-effects models based on worldwide data, the summarized means (95% CIs) as percentages of total fat were 42.2% (41.1%, 43.3%) for SFAs, 36.6% (35.6%, 37.5%) for MUFAs, and 21.0% (19.3%, 22.7%) for PUFAs. However, the study heterogeneity was high for most types of fatty acids (I2 > 99%). Human milk from Western countries had higher concentrations of MUFAs and 18:1n-9 (ω-9), but lower concentrations of PUFAs, 18:2n-6, 20:4n-6, 18:3n-3, 20:5n-3, 22:6n-3, and total n-6 PUFA compared with those from non-Western countries (P < 0.001-0.011). Significant lactation stage differences were observed for total fat and some individual fatty acids. The concentrations of SFAs and 16:0 were significantly negatively correlated with sampling year (P < 0.001-0.028). In contrast, a significant positive correlation between the concentrations of 18:2n-6 and 18:3n-3 and sampling year was observed (P < 0.001-0.035). Our results suggest that the pooling of data on human milk lipid profiles in different studies should be done with caution due to the high between-study heterogeneity. The concentration of lipids, including total fat, cholesterol, and specific fatty acids, differs in human milk according to lactation stage, geographical region, and year of sample collection.

New Methodologies for Conducting Maternal, Infant, and Child Nutrition Research in the Era of COVID-19

The severe acute respiratory syndrome coronavirus disease 2019 (COVID-19) outbreak rapidly became a worldwide pandemic in early 2020. In Australia, government-mandated restrictions on non-essential face-to-face contact in the healthcare setting have been crucial for limiting opportunities for COVID-19 transmission, but they have severely limited, and even halted, many research activities. Our institute's research practices in the vulnerable populations of pregnant women and young infants needed to adapt in order to continue without exposing participants, or staff, to an increased risk of exposure to COVID-19. Here, we discuss our pre-and-post COVID-19 methods for conducting research regarding nutrition during pregnancy, infancy, and early childhood. We discuss modifications to study methods implemented to avoid face-to-face contact when identifying and recruiting potential participants, gaining informed consent, conducting appointments, and collecting outcome data, and the implications of these changes. The COVID-19 pandemic has required numerous changes to the conduct of research activities, but many of those modifications will be useful in post-COVID-19 research settings.

Free Fatty Acid Concentration in Expressed Breast Milk Used in Neonatal Intensive Care Units

Preterm and sick term infants are commonly fed with expressed breast milk (EBM) that has been subjected to various storage and handling conditions before feeding that may cause lipase-mediated elevation of free fatty acids (FFA). This study was designed to describe the variation, between mothers' and within the same mother over time, in the concentration of FFA in EBM used in an Australian neonatal unit. A total of 256 EBM samples, 149 freshly expressed in the unit cot-side and 87 expressed at home and brought in to the unit, were collected from 32 mothers with an infant admitted to the neonatal intensive and/or special care units at the Women's and Children's Hospital, Adelaide. Among the fresh EBM samples collected cot-side, the average total fat content was 29.78 ± 9.28 mg/mL, and the FFA concentration was 1.70% of total fats (interquartile range [IQR]: 1.17-2.37%). Among the 10 mothers who provided fresh EBM at different stages of lactation, the concentration of FFA remained low overall, with some day-to-day variation (min 0.58% and max 5.0% of total fats within the same mother). The average total fat content of home collected EBM was similar to the cot-side collected samples, at 27.37 ± 8.23 mg/mL, and the FFA concentration was slightly higher at 2.49% of total fats (IQR: 1.74-3.29%). Overall, the FFA concentration of breast milk in the neonatal unit before and even after a short period of cold storage and handling is universally low.