New study examines how gut bacteria may influence food allergy risk in infants 

A recent study led by researchers at the RIKEN Centre for Integrative Medical Sciences (IMS) in Japan has provided new insights into the relationship between gut bacteria and food allergies, particularly to eggs. The findings suggest that certain types of bacteria are linked to food sensitisation, while others do not appear to contribute to this risk. This study also identified factors that predict which types of bacteria will be present in newborns, offering valuable information on early gut microbiota development and its potential role in food allergy risk. 

How did the study work? 

This study analysed gut bacteria data from two long-term studies that followed children from birth until the age of 7. One group consisted of 270 children with a family history of allergies, putting them at a higher risk, while the other group included 245 children from a previous allergy treatment study.  

This allowed researchers to connect early gut bacteria patterns with later allergy development. The study involved analysing two main types of data collected over time: 

1. IgE antibody levels in the blood (measured from age one to seven), which indicate sensitivity to common food allergens such as milk, peanuts, egg whites, and wheat. 

2. Gut bacteria composition, starting when the children were just one week old. 

By combining these two sets of information, they hoped to discover whether certain gut bacteria compositions could predict who would develop food sensitivities or allergies. 

What did the study find? 

To understand the link between gut bacteria and allergy development, the researchers grouped the children’s gut bacteria into distinct patterns called “enterotypes.” They identified six different enterotypes across all the children in the study. They found that the enterotypes present when the babies were one month old showed the strongest relationship to the levels of food-specific IgE antibodies in their blood later in life (over the seven-year period). 

Specifically, when looking at one-month-old babies, they identified three main enterotypes: 

1. Bacteroides-dominant: where the gut bacteria is mainly Bacteroides. 

2. Klebsiella-dominant: where the gut bacteria is mainly Klebsiella. 

3. Bifidobacterium-dominant: where the gut bacteria is mainly Bifidobacterium. 

The key findings, linking these early enterotypes to later allergy risk, include: 

• The gut bacteria composition at one month old was a better predictor of future food sensitivities and allergies than the bacteria composition at just one week old. 

• Infants with a Bifidobacterium-dominant enterotype at one month had the lowest risk of developing food sensitivities and allergies, especially to hen egg white. 

• This protective effect of the Bifidobacterium-dominant enterotype continued to be seen in some of the children even at nine months (in one of the studies) and at two years old (in the other study). Meaning, the Bifidobacterium-dominant enterotype continued to show lower risk of allergies and sensitivities compared to infants with Bacteroides- or Klebsiella-dominant enterotypes. 

• The Bifidobacterium-dominant gut profiles also had the highest levels of a compound called propionate, which is a short-chain fatty acid produced when bacteria break down certain fibres. 

What’s next? 

These findings highlight the potential role of a healthy gut microbiome in early infancy as a key factor in reducing food allergy risk. This could pave the way for new strategies to prevent food allergies in the future. 

Since gut bacteria are influenced by factors such as diet, birth method (vaginal or caesarean), and antibiotic use, there may be opportunities to support the development of beneficial microbes during early infancy. 

However, as this research was conducted in Japan, and gut microbiomes can vary across populations and regions, further studies in diverse groups will be essential to confirm and expand on these findings. 

The study was published in the Journal of Allergy and Clinical Immunology. You can read the full report here: https://www.jacionline.org/article/S0091-6749(24)01173-4/fulltext.