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This review critically evaluates current in vitro gastrointestinal models for assessing infant formulas from a perspective focusing on a process along digestion, absorption and microbial fermentation. Despite their potential, none of the current in vitro gastrointestinal models fully considers the dynamics and continuous upstream‐downstream process of the human digestive tract. Considering the substantial differences between infants and adults, there is a pressing need for whole‐process gastrointestinal models tailored to infants. Developing such models is crucial for accurately assessing infant formula nutritional value and physiological function, enhancing the formulation of infant formulas to better meet the needs of infants. [ABSTRACT FROM AUTHOR]

Human milk is universally regarded as the gold standard to fulfill nutrition needs of infants. Lactoferrin (LF) is a major multiple bioactive glycoprotein in human milk but little is presented in infant formula. LF can resist digestion in the infant gastrointestinal tract and is absorbed into the bloodstream in an intact form to perform physiological functions. Evidence suggest that LF prevents pathogen infection, promotes immune system development, intestinal development, brain development and bone health, as well as ameliorates iron deficiency anemia. However, more clinical studies of LF need to be further elucidated to determine an appropriate dosage for application in infant formula. LF is sensitive to denaturation induced by processing of infant formula such as heat treatments and spay drying. Thus, further studies should be focus on maximizing the retention of LF activity in the infant formula process. This review summarizes the structural features of LF. Then the digestion, absorption and metabolism of LF in infants are discussed, followed by the function of LF for infants. Further, we summarize LF in infant formula and effects of processing of infant formula on bioactivities of LF, as well as future perspectives of LF research. [ABSTRACT FROM AUTHOR]

[Display omitted] • Endogenous DHA in milk is more bioaccessible than exogenously added DHA. • Endogenous DHA in milk has higher digestive stability than exogenously added DHA. • The bound form of milk endogenous DHA facilitates its digestion and absorption. • Naturally enriched milk fat hydrolyzes easier than artificially enriched milk fat. This study aimed to compare the bioaccessibility of docosahexaenoic acid (DHA) in naturally and artificially enriched milk and investigate the potential mechanisms involved. The results indicated that the DHA in naturally enriched milk (NEM) had a higher bioaccessibility (76.9 %) and a lower digestive loss rate (18.1 %) compared to artificially enriched milk (ArEM). Moreover, NEM contained a higher proportion of DHA-containing glycerophospholipids and sn -2 DHA, with fewer long-chain fatty acids and more saturated fatty acids adjacent to DHA in the same lipid molecule. During simulated intestinal digestion, NEM had a higher free fatty acid release and lipid digestion rate than ArEM. These findings suggested that the bioaccessibility of endogenous DHA in milk was superior to that of externally added DHA due to its more easily digestible and absorbable chemical binding form and lower digestive loss rate. The easy digestibility of milk lipids in NEM also contributed to its high DHA bioaccessibility. [ABSTRACT FROM AUTHOR]

The recommended amino acid requirements of the infant are based on the amino acid composition of mature human breast milk. The amino acid composition of breast milk is usually determined following either acid or alkaline (for tryptophan) hydrolysis. For accuracy, however, the known effect of hydrolysis time on amino acid composition should be accounted for. Also, ideally the amino acid composition of breast milk should be given in units of digested (assumed to be absorbed) amino acids. A review of the literature is presented which gives mean total amino acid concentrations in mature human milk ( n  = 26 studies), mean hydrolysis correction factors ( n  = 3 studies) and mean true ileal amino acid digestibility coefficients ( n  = 3 studies, suckling piglet). There were differences between the estimates of amino acid concentration corrected for hydrolysis time and digestibility, and current FAO (2013) recommendations that were not corrected for these factors. The values based on the published literature up until 2023 (mg/g true protein) corrected for hydrolysis time and digestibility gave higher values (more than 16% higher) for leucine, lysine and threonine, and considerably higher values (greater than 30%) for histidine and tryptophan. Current recommendations may need revision., Competing Interests: YY, SD, and IS were employed by Inner Mongolia Dairy Technology Research Institute Co. Ltd. PW was employed by Oceania Dairy Limited. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Moughan, Deglaire, Yan, Wescombe, Lim, Stroebinger, Duan, Szeto and Hodgkinson.)

Long-chain polyunsaturated fatty acids (LC-PUFAs), arachidonic acid (ARA, 20:4n-6) and docosahexaenoic acid (DHA, 22:6n-3) are essential in the development of infants. ARA and DHA from breast milk or infant formula are the main sources of access for infants to meet their physiological and metabolic needs. The ratio of ARA to DHA in breast milk varies among regions and different lactation stages. Different ratios of ARA and DHA mainly from algal oil, animal fat, fish oil, and microbial oil, are added to infant formula in different regions and infant age ranges. Supplementing with appropriate ratios of ARA and DHA during infancy promotes brain, neural, visual, and other development aspects. In this review, we first introduced the current intake status of ARA and DHA in different locations, lactation stages, and age ranges in breast milk and infant formula. Finally, we discussed the effect of different ratios of ARA and DHA on infant development. This review provided a comprehensive research basis for the nutritional research of infants who consume different ratios of ARA and DHA.