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Supplemental bionutrients: proteins and sugars

Professor Virgilio Carnielli and Professor Nicholas Embleton introduce the supplemental bionutrients, beginning with proteins and sugars.
Professor Nicholas Embleton (left) and Professor Virgilio Carnielli (right).

Hello, we would like to introduce the next two steps, where we will be covering the role of supplemental bionutrients in preterm enteral nutrition.

Breastmilk is known to contain certain bionutrients that are beneficial to the infant in particular ways. Being able to harness these molecules and synthesise them ourselves to supplement enteral feeds is potentially a very useful tool to ensure appropriate infant development. We will now expand on the main types of bionutrients in further detail.

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Multiple components present in human breastmilk (some of which are also present in other mammalian milks) have been explored as potential ‘bionutrients’ or ‘immuno-nutrients’ that could be added to enteral feeds in preterm infants.

The components of breastmilk being investigated, including some key examples, are shown in the graphic below:

Potential bionutrients from breastmilk. These include bio-nutrient complexes such as milk-fat globule membrane, vitamin-like compounds and carotenoids such as choline and lutein, enzymes such as bile-salt stimulated lipase, sugars such as human milk oligosaccharides, nucleuotides, and proteins and lipids such as lactoferrin.

These bionutrients may be synthesised (e.g. recombinant BSSL or recombinant human lactoferrin), derived from bovine milk (e.g. lactoferrin or MFGM) or come from other sources (e.g. lutein).

In this step, we will focus on the sugar and protein components (including enzymes), before moving on to the other supplemental bionutrients. We acknowledge there are several lipids (for example, DHA) that are potential bionutrients, but they were not reviewed by ESPGHAN as part of the current position paper.


Lactoferrin is a glycoprotein in the whey fraction of mammalian milk and is present in human colostrum in much higher concentrations than mature human milk or bovine based milk formula. Actions of lactoferrin demonstrated in vivo or in vitro include:

In the centre of the spider diagram is 'lactoferrin' with lines pointing to the following: immune development, brain development, promotes beneficial bacteria e.g. Bifidobacteria, deprives pathogenic bacteria access to iron, anti-bacterial, anti-viral, anti-fungal.

Most neonatal studies have used supplemental bovine lactoferrin, which is widely available and cheap. Some have tested recombinant human lactoferrin, which is more expensive. Studies suggest that although the in vitro activity of human and bovine lactoferrin appears similar, important structural and functional differences exist.

A Cochrane meta-analysis in 2017 of 6 trials provided low certainty of evidence for a reduction in late-onset sepsis (LOS) (RR 0.59, 95% CI, 0.40-0.87) and NEC (RR 0.46, 95% CI, 0.29-0.74). The ELFIN study is the largest trial to date, including 2203 very preterm infants, and showed no significant impact on sepsis or NEC. However, an updated 2019 meta-analysis by Razak et al concludes that a reduction in sepsis may be still present.


If you require a screen-reader compatible version this is available as a PDF.


If you require a screen-reader compatible version this is available as a PDF.


Inositol is a 6-carbon sugar alcohol present in biological systems primarily as myo-inositol and is required for mammalian cell growth and survival. Inositol and its derivatives are involved in a multitude of processes including:

Signaling pathways, enzyme activation, lipid synthesis, maturation of several components of surfactant.

Historical studies in preterm infants suggested further supplementation might reduce the rate of respiratory distress syndrome, and some more recent studies also suggested reductions in death, intra-ventricular haemorrhage, and ROP. However, the largest study to date was stopped prematurely after 638 of the planned 1760 infants were recruited, due to significantly higher mortality in the myo-inositol intervention group. The most recent meta-analysis demonstrates no overall benefit of additional inositol supplementation for any key neonatal outcome.


If you require a screen-reader compatible version this is available as a PDF.


If you require a screen-reader compatible version this is available as a PDF.

Human milk oligosaccharides (HMOs)

Human milk oligosaccharides (HMOs) are non-digestible carbohydrates and are the third largest solid component in human milk after lactose and lipids. There are more than 200 unique HMOs present in human milk and their structure is different to oligosaccharides in other mammalian milks.

HMOs are resistant to pasteurisation and freeze-drying. Their concentrations in breastmilk change during lactation, in addition to differences reflecting genetic and environmental factors.

There are a number of significant impacts that HMOs may have on preterm infants, some of which are outlined in the infographic below.

Immune function, for example, protection against NEC and sepsis. Gut health, for example, promoting a bifidobacteria-dominated gut microbiota. Brain development.

These effects are likely to involve multiple mechanisms and benefits, and may be modulated through signalling pathways of enterocytes and/or by modulating the gut microbiota. For example, human milk is especially rich in fucosylated HMOs, especially 2-FL, which are responsible for promoting a bifidobacteria-dominated gut microbiota.

Recently, oligosaccharides structurally identical to some of those in human milk have been synthesised artificially. No RCTs have been conducted in preterm infants but observational studies have associated specific HMO profiles with a lower incidence of NEC.


If you require a screen-reader compatible version this is available as a PDF.


If you require a screen-reader compatible version this is available as a PDF.

Bile salt simulated lipase (BSSL)

© SciencePhotoLibrary, Canva, 2022

Bile Salt Stimulated Lipase (BSSL) is a lipolytic enzyme in human milk and is similar to bile-salt dependant lipase (BSDL) that is expressed in all mammalian species in the exocrine pancreas. BSSL is secreted into the intestinal lumen to facilitate digestion and absorption of dietary fat. In the gastrointestinal (GI) tract, BSSL has broad specificity and hydrolyses a variety of different substrates including tri-, di-, and monoglycerides, cholesteryl and retinyl esters, phospholipids, and ceramides.

Exocrine pancreatic function is not fully developed at birth, and BSDL production may be insufficient in preterm infants to fully support fat absorption. In humans, BSSL is also secreted by the lactating mammary gland, which may partially compensate for the lower endogenous production of BSDL in preterm infants.

Breastmilk-derived BSSL, once activated by endogenous bile salts in the upper small intestine, contributes to the efficient use of milk fat in breastmilk-fed infants. BSSL may therefore be important for healthy growth and development in preterm infants.

A recombinant human BSSL (rhBSSL) has been developed and produced as an oral therapeutic strategy to improve lipid absorption. Two studies explored the effect of rhBSSL supplementation in preterm infants. In the first cross-over study, one week of rhBSSL supplementation significantly improved growth velocity and the absorption of docosahexaenoic acid (DHA) and arachidonic acid (ARA), but there were no significant effects on total fat absorption. In a larger RCT, there were no significant effects on growth or several other secondary endpoints.


If you require a screen-reader compatible version this is available as a PDF.


If you require a screen-reader compatible version this is available as a PDF.
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Enteral Nutrition in Preterm Infants: ESPGHAN Recommendations

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