1. Introduction
Human milk is recognized as the best food for newborns, rich in lipids,
proteins, carbohydrates, and other micronutrients to ensure the enough
energy and nutrients for newborns for growth and development (Harding et
al., 2017). The World Health Organization (WHO) recommends exclusive
breastfeeding for the first six months of life of infants (Eidelman et
al., 2012). Lipids are important nutrients in breast milk, accounting
for about 3-5% and providing 50-60% of the newborn’s energy
(Demmelmair and Koletzko, 2018). Human milk lipids are reported as
variable influenced by many factors for example individuals, lactational
period, maternal dietary etc (Grunewald et al., 2019; Burianova
et al., 2019; Gridneva et al., 2022; Ye et al., 2021).
The fatty acid (FAs) profiles in human breast milk have been
well-studied worldwide (Liu et al., 2018). Recent studies show that
triacylglycerols (TAGs) in human breast milk have unique molecular
structure and showing important roles for infant lipid digestion and
metabolism. Previously, we analyzed the TAG composition of Chinese human
milk, found a group of TAG containing both medium-chain fatty acids
(MCFAs) and long-chain fatty acids (LCFAs) esterified at one glycerol
backbone, namely medium- and long-chain triacylglycerol (MLCT) (Yuan et
al., 2020). According to the number of medium-chain fatty acid (MCFA)
and long-chain fatty acids (LCFAs) on the glycerol backbone, MLCT can be
divided into two types,the MLCT esterified with one MCFA and two LCFAs
are the MLL type; and the MLCT esterified with two MCFAs and one LCFA
are the MML type. In human milk, MLCT types of TAGs contains
approximately 40 kinds of TAGs, accounting for 20-30% of total TAG
(Zhang et al., 2021; Yuan et al., 2021). There are obvious differences
of the MLCT content and molecular species in lipids between human milk.
Compared with LCT, MLCT has not only long-chain fatty acids, but also
medium-chain fatty acids. Due to the presence of MCFA, it is more
conducive to the direct absorption and utilization of infants, MLCT will
have higher lipolysis degree as well as release higher levels of free
fatty acid in infant intestinal digestion (Yuan et al., 2020; Wang et
al., 2022), therefore MLCT is conducive to the digestion and absorption
of lipids, providing fast energy (Yu et al., 2022a). In addition, MLCT
has more incorporation of long-chain fatty acids than MCT, allowing it
to provide the physiological activities of the body (Lee et al., 2022).
Previous studies show that FAs in human milk are highly influenced by
the maternal diet (Ward et al., 2021; Wang et al., 2010). The content of
protein, and lactose in breast milk was not obviously affected by the
breast milk diet, but the fatty acids in breast milk were affected by
the mother ’s immediate diet (Aumeistere et al., 2019). There are also
studies of Nigeri mothers that high carbohydrate intake leads to higher
MCFA in breast milk, while excessive intake of fat may lead to lower
levels of MCFA (VanderJagt et al., 2000), Sudan (Nyuar et al., 2010),
and Egypt (Bakry et al., 2021) show high content of 12:0 and 14:0, which
were approximately 20% of total fatty acids. Current studies have shown
that MCFAs are affected by dietary structure, but the relationship
between TAG containing MCFAS and dietary patterns in breast milk is
rarely studied.
This study aims to analysis the correlation between MLCT content &
molecular species and maternal dietary patterns. This study collected
mature breast milk samples and dietary intake data of healthy Chinese
lactating women 30-90 days postpartum . A total of 180 volunteer
mothers were divided into three groups fat group (> 30
energy %, n = 60), carbohydrate group (> 50 energy
%, n = 60), and protein group (>15 energy %,n = 60) according to Yang (Yang, 2018). recommendations. TAGs
were identified and quantified using High Performance Liquid
Chromatography-Mass Spectrometry (LC-MS) following our previous studies.
The composition of MLCTs in breast milk and their relationship with
nutrient energy supply ratio were clarified, which provided scientific
basis for developing novel structured lipids used in infant formula.