Acidified infant milk and postbiotics

The term postbiotics refers to soluble products or metabolic by-products secreted by live bacteria (probiotics), or released after bacterial break down, such as enzymes, peptides, oligosaccharides, polysaccharides, cell surface proteins, and organic acids. It is being suggested that postbiotics may have anti-inflammatory, immunomodulatory, antiobesogenic, antihypertensive, hypocholesterolemic, anti-proliferative, and antioxidant activities (Aguilar-Toalâ et al, 2018). These suggested properties could mean that postbiotics might contribute to the improvement of host health by improving specific physiological functions. Currently mechanisms of action for postbiotics have not been entirely elucidated.

The presence of postbiotics in infant milks is not a new development as 'acidified' infant milks produced by fermentation with lactic acid producing bacteria have been available in other European countries such as France and in African countries for many years. They contain postbiotics and have been described as:

“Infant and follow-on formulae that have been fermented with lactic acid-producing bacteria during the production process, but do not contain live bacteria in the final product due to inactivation of the fermenting bacteria by heat treatment or other means". (ESPGHAN, 2007).

They have typically been marketed as being useful in preventing a range of gastrointestinal symptoms and, in particular, in preventing diarrhoeal disease. Despite widespread use globally, there is little published data available to support their use.

There are a small number of studies that have investigated the effects of fermented infant milks on diarrhoeal disease amongst infants who are receiving complementary foods. Brunser et al,1989 showed a reduction in the incidence of diarrhoea as well as a lower proportion of days with diarrhoea and shorter duration of episodes in Chilean children fed acidified Nestlé Pelargon formula, compared to those receiving the same formula but non acidified. In a more recent controlled clinical trial that examined the effect of a fermented formula on the incidence of acute diarrhoea in healthy 4–6-months-old infants, reductions in the severity, but not in the incidence of diarrhoea were reported. The outcomes of this trial were based on parental report and 4 visits with a paediatrician. The trial was sponsored by Blédina (Nutricia). There was no breastfed reference group and the milk did not contain prebiotics. Neither the composition of the milk, nor the proportion of fermented milk used were disclosed (Thibault et al, 2004).

Recent additions to the formula milk market in the UK have included infant milks containing approximately a quarter of their whey component from milk fermented with the lactic acid producing bacteria Bifidobacterium breve and Streptococcus thermophiles. These milks therefore contain metabolites from the fermentation process but do not contain live bacteria. Despite this, the milks are not marketed as acidified or fermented milks but as containing postbiotics, a new ingredient. Infant milks that contain a proportion of fermented milk claim to also contain 3’-galactosyllactose, this HMO is produced as a result of the fermentation of the cows’ milk used in the product mix.

A number of claims have been made about the use of postbiotics in combination with a prebiotic GOS:FOS mix including:

‘Gut and immune markers closer to breastfed infants' and 'This combination of prebiotics and postbiotics have been shown to support a healthy gut in infants, important for immune system development and functioning.'

In 2007 The ESPGHAN Committee on Nutrition carried out a systematic review of the literature to assess knowledge on the effects of fermented infant formula without live bacteria. They concluded that "the published data on the effects of fermented infant formulae without live bacteria are limited and do not allow firm conclusions" and that "the effects of fermented infant formulae on infectious diarrhea and other relevant outcomes should be assessed in further randomized controlled trials" (Agostoni et al, 2007)

References

Agostoni C, Goulet O, Kolacek S, et al (2007). Fermented Infant Formulae Without Live Bacteria: Medical position paper by the ESPGHAN Committee on Nutrition. Journal of Pediatric Gastroenterology and Nutrition, 44, 392-397.

Aguilar-Toala JE, Garcia-Varela R, Garcia HS, Mata-Haro V et al (2018) Postbiotics: An evolving term within the functional foods field. Trends in Food Sci and Chem, 75, 105-114

Brunser O, Araya M, Espinoza J et al (1989). Effect of an acidified milk on diarrhoea and the carrier state in infants of low socio-economic stratum. Acta Paediatrica Scandanavia, 78, 259–264

Thibault H, Aubert-Jacquin C, Goulet O (2004). Effects of long-term consumption of a fermented infant formula (with Bifidobacterium breve c50 and Streptococcus thermophilus 065) on acute diarrhea in healthy infants. Journal of Pediatric Gastroenterology and Nutrition, 39, 147-152.