Prebiotics are non-digestible food components that have the ability to enhance the growth and/or activity of some beneficial bacteria. Prebiotics are sometimes confused with probiotics, which are live beneficial bacteria. Instead, prebiotics encourage the growth and activity of these same bacteria already existing in the gut. Prebiotics are mostly found in plant-based foods including bananas, asparagus, onion and artichoke.

General health

In adults, prebiotic supplementation may benefit gut health by reducing IBS symptoms and the risk of contracting traveller’s diarrhoea.(1, 2) In one study, prebiotic intake was associated with positive immune effects including increased phagocytosis, natural killer cell activity, and production of anti-inflammatory interleukin-10 (IL-10).(3) In the same study, researchers found it also reduced the production of pro-inflammatory cytokines (IL-6, IL-1 and tumour necrosis factor-α).(3) The beneficial effects of prebiotics are most likely secondary to the increase in Bifidobacteria spp. that follows supplementation. Bifidobacteria are well-recognised beneficial bacteria that play an important role in the gut microbiome. Low levels of Bifidobacteria in the gut are associated with several health conditions including coeliac disease, irritable bowel syndrome, allergies, and metabolic syndrome.(4-7)

Prebiotics in infant formula

Human breast milk contains natural prebiotics called human milk oligosaccharides (HMOs). They are the third largest component of human milk and promote healthy development of the infant’s microbiome. Dietary oligosaccharides that have similar prebiotic effects to HMOs include galacto-oligosaccharides (GOS), fructo-oligosaccharides (FOS), and pectin-derived acidic oligosaccharides. GOS and FOS are found in the non-digestible components of foods, commonly including legumes, wheat and rye products, onion and garlic. Since HMOs, GOS and FOS are not actually digested, they pass through to the colon where they have beneficial effects.

The composition of breast milk is still not entirely understood in scientific literature, but there have been significant breakthroughs in finding key components that benefit developing infants. Infant formulas are constantly being reformulated in response to these discoveries with the aim of providing similar benefits to breast milk. For example, some infant formulas are now supplemented with prebiotic GOS, FOS, or both. Additionally, certain HMOs, structurally identical to those found in breast milk, are available to add to infant formula products.(8) While over 200 different HMOs have been identified in breast milk, only a limited number have been approved for use in infant formula in Australia.

Studies comparing the effects of GOS- and FOS-supplemented infant formula with standard infant formula have demonstrated beneficial effects of these prebiotics.

Infants given formula supplemented with GOS or FOS show signs of improved gastrointestinal health compared with those fed non-supplemented formula.(9) These benefits can include changes in short-chain fatty acids, lactate and pH that more closely resemble the fermentation profile observed in breastfed infants.(9) Those fed supplemented formula also had higher levels of Bifidobacterium spp. compared with infants fed standard formula.(1, 9-14) Bifidobacteria reduce the amount of pathogens in faecal flora and may provide some protection against intestinal infections in infants.(15)

Some studies have found a dose-dependent relationship between the amount of GOS and/or FOS in infant formula and softer stools that are more similar to breastfed infants.(10, 12) Compared with other prebiotics, GOS is generally best tolerated and results in only a small amount of gas production.(14) It is important to note that beneficial effects of GOS-supplemented infant formula may only be seen when administration commences in the first few months of life.(16) The effects may also be short-term, as bacterial populations return to baseline levels one to two weeks after GOS consumption ceases.(11)

A Cochrane review found that formula-fed infants were less likely to develop eczema if their formula contained prebiotics; however, this did not extend to asthma or hives.(17) There are fewer Bifidobacteria and more clostridia and Staphylococcus aureus in the microbiome of infants who develop allergies later in life.(18) There is significant evidence that the microbiome is related to immune function. As scientific understanding of this relationship improves, it may become possible to manipulate the microbiome for immune benefits.(18, 19) But further research is needed before recommending prebiotics for allergy prevention in infants.

Breastfeeding

Infant formula supplemented with GOS and/or FOS is unlikely to provide equal benefits to HMOs naturally in breast milk. Even with the addition of structurally identical HMOs, infant formula cannot fully replicate the diversity and complexity of the variety of HMOs in breast milk.(8) It is well understood that breast milk provides the best nutrition for infants. But when breastfeeding is not possible, infant formula supplemented with prebiotics may be a better option than standard formulas. The current literature suggests that infants consuming supplemented formulas have similar colonic microbial environments to that in breastfed infants.(1, 9-14) Whether breastfeeding or formula-feeding, the developing baby will ultimately consume naturally occurring prebiotics when they commence intake of solids.