Branched-chain fatty acid composition of human milk and the impact of maternal diet: the Global Exploration of Human Milk (GEHM) Study

Abstract

Background: An understudied component of the diet, branched-chain fatty acids (BCFAs) are distinctive saturated fatty acids that may have an important influence on health. Human-milk fatty acid composition is known to differ worldwide, but comparative data are lacking on BCFAs.

Objective: We tested the hypotheses that concentrations of BCFAs in human milk differ between populations and are associated with maternal diet.

Design: We surveyed the BCFA composition of samples collected as part of a standardized, prospective study of human-milk composition. Mothers were enrolled from 3 urban populations with differing diets: Cincinnati, Ohio; Shanghai, China; and Mexico City, Mexico. Enrollment was limited to healthy mothers of term singleton infants. We undertook a cross-sectional analysis of milk from all women with samples at postpartum week 4 (n = 359; ∼120 women/site). Fatty acids were extracted from milk by using a modified Bligh-Dyer technique and analyzed by gas chromatography. Statistical analysis was performed by ANOVA and Tobit regression. For Cincinnati mothers, 24-h diet recalls were analyzed in relation to the individual BCFA concentrations measured in milk samples.

Results: Total BCFAs in milk differed by site, with the highest concentration in Cincinnati followed by Mexico City and Shanghai (mean ± SE: 7.90 ± 0.41, 6.10 ± 0.36, and 4.27 ± 0.25 mg/100 mL, respectively; P < 0.001). Site differences persisted after delivery mode, maternal age, and body mass index were controlled for. The individual concentrations of iso-14:0, iso-16:0, iso-18:0, anteiso-15:0, and anteiso-17:0 also differed between sites. Milk concentrations of iso-14:0 and anteiso-15:0 were associated with maternal intake of dairy; iso-16:0 was associated with maternal intakes of dairy and beef.

Conclusions: BCFA concentrations in milk at 4 wk postpartum differed between mothers from Cincinnati, Shanghai, and Mexico City. Variations in human-milk BCFAs are influenced by diet. The impact of BCFAs on infant health warrants investigation.

Keywords: branched-chain fatty acids; fatty acids; human milk; lactation; maternal diet.

FIGURE 1

The BCFA with a terminal isopropyl group represents an iso-BCFA (A) and that with a terminal isobutyl group represents an anteiso-BCFA (B). MarvinSketch (MarvinSketch 16.6.20, 2016; ChemAxon; http://www.chemaxon.com) was used for drawing, displaying, and characterizing chemical structures, substructures, and reactions. BCFA, branched-chain fatty acid.

FIGURE 2

Box plots showing medians and IQRs of total BCFAs by site. Panel A presents total BCFA concentrations (mg/100 mL) by site. Panel B presents BCFAs as a percentage of total FAs by site (BCFAs divided by the sum total of FAs determined included 10:0–22:6n–3). The top and bottom of each box plot represents the 25th and 75th percentiles, and whiskers indicate 1.5 times the IQR. Data points set outside these limits are plotted. BCFA, branched-chain fatty acid; FA, fatty acid.

FIGURE 3

Box plots showing medians and IQRs of individual BCFAs by site. Panel A presents BCFA concentrations (mg/100 mL) by site. Panel B presents individual BCFAs as a percentage of total BCFAs by site. Plots include imputed data for values below the limit of detection. Single imputation was performed from a truncated log-normal distribution with means ± SDs obtained from Tobit regression. The top and bottom of each box plot represents the 25th and 75th percentiles, and whiskers indicate 1.5 times the IQR. Data points set outside these limits are plotted. BCFA, branched-chain fatty acid.