ASSIGN study: A synbiotic-containing amino acid-based formula improves gut microbiota in non-IgE-mediated allergic infants

Study title

A synbiotic-containing amino acid-based formula improves gut microbiota in non-IgE-mediated allergic infants.

Official registration:

Study objectives

The primary objective of this study was to assess the effect of an amino acid-based formula (AAF) with a specific synbiotic blend on the bacterial composition (specifically bifidobacteria and the E. rectale/C. coccoides group) of faecal samples of infants with suspected gastrointestinal non-IgE-mediated Cow’s Milk Allergy (CMA), compared with an AAF without synbiotics at 8 weeks.

Secondary outcomes were stool characteristics, frequency and consistency at 0, 1, 4 and 8 weeks, as well as parameters of gut health and immune status (measured by faecal secretory IgA and Short Chain Fatty Acids at weeks 0 and 8).


Infants who suffer from CMA have been shown to have a dysbiosis of gut microbiota. It has been found that levels of key bacterial strains, i.e. bifidobacteria in particular, are lower in infants with CMA as compared with healthy, breastfed infants.

Previously the AAF formula with synbiotics has been clinically shown in CMA infants to effectively resolve food allergy symptoms and to support adequate growth and development (Harvey et al (2014); Burks et al (2015)).

The ASSIGN study is a multi-centre, randomised, double-blind, controlled, study to investigate the effect of an AAF with specific synbiotics on the bacterial composition of faecal samples of infants with suspected non-IgE mediated CMA. Healthy breastfed infants were selected as reference group.

At screening, infants <13 months of age were included based on predefined in- and exclusion criteria. Data on medical history, subject’s characteristics, medications and feeding history were also collected. At baseline, 71 cow’s milk allergic infants meeting the inclusion criteria underwent a clinical assessment of their allergic symptoms, including the collection of a stool sample. Subjects were then randomised to receive either an AAF with synbiotics, or an AAF without synbiotics for eight weeks.

Parents/guardians were also instructed to complete a diary and asked to log details relating to acceptance and tolerance of the study formula.
At the visit in week 8 (first results published) and follow up visits at week 12 and week 26, a further clinical assessment of allergic symptoms was carried out using clinician rating scales. The parent diary plus infant stool were collected during these visits. Percentages of bifidobacteria and other bacterial groups were determined in faeces using fluorescence in situ hybridisation (FISH).

UK, Italy, Belgium and Sweden.


Results at week 8 showed the median percentage of bifidobacteria was higher in the test group than in the control group (35.4% vs. 9.7%, respectively; P<0.001), whereas ER/CC (E. rectale/C. coccoides group) was lower (9.5% vs. 24.2%, respectively; P<0.001). Levels of bifidobacteria and ER/CC in the healthy reference group were 55% and 6.5%, respectively.

The ASSIGN study concludes the hypoallergenic amino acid-based formula (AAF) brings the gut microbiota of infants with cow’s milk allergy (CMA) closer to that of healthy breastfed infants.

Read the full publication here.