Key Message: Gut microbiome composition is associated with temperament during early childhood.

Action point: Ensure your child’s microbiome is supported with appropriate probiotics. I use probiotic therapy in all my little patients with great success.

happy boy

Had a gut-full of your two-year-old’s tantrums? Believe it or not, their digestive health might be contributing to the problem.

Microbes in the GI tract may play a surprising role in toddler temperament, according to a new study from the Ohio State University1.

Researchers have become increasingly interested in how the population of bacteria in the gut (known as gut microbiome) affects health. Studies have already linked gut bacteria to conditions including obesity, allergies and bowel disease. Now researchers are interested in finding out if gut bacteria is also linked to mood and behaviour.

The complex ecosystem of microbes living in the gastrointestinal tract is known to change considerably in the first two years of life, especially as solid foods are introduced into a child’s diet. And according to a new study, this unstable “gut microbiome” and a toddler’s temperament are linked.

The importance of the gut in early life

Determining the dynamics of the behaviour–gut associations in early life is important for a number of reasons. Firstly, many physical and mental health conditions such as obesity and anxiety have early life precursors. Also, research suggests that the gut microbiome may be more malleable in early versus later life.

By approximately two years of age, our gut microbiota is established and relatively stable. Although the gut microbiome changes in response to illness, diet and antibiotics, the overall profile tends to revert to normal after the disruption has passed.

The study

For the study, the researchers examined the different genetic types and varying amounts of bacteria found in stool samples from 41 boys and 36 girls between the ages of 18 and 27 months. The researchers also surveyed the children’s mothers about the kids’ temperament and eating patterns.

They found that the abundance and diversity of bacteria found in the gut appear to influence the behaviour of young children, especially young boys. Children who were described as extroverted and upbeat tended to have more genetically diverse bacteria in their stool – and that might mean there’s a link between microbial diversity and a more positive temperament.

However, the researchers warned that this does not mean that parents can rein in an unruly toddler simply by changing his or her diet.

While the study found a link, it is impossible to say whether the bacteria actually caused the behaviour, or whether other factors are responsible for the link seen. And it’s still unknown what a healthy combination of gut bacteria might look like, or how it might influence other aspects of a child’s behaviour or health.



Christian LM, Galley JD, Hade EM, et al. (2014) Gut microbiome composition is associated with temperament during early childhood. Brain, Behavior and Immunity. 45:118-127. Published online November 10 2014. doi:10.1016/j.bbi.2014.10.018

Kat Boehringer 
Freelance journalist and editor 

Kat Boehringer specialises in health communications including health writing, health promotions, and social media management. In her spare time she works as a massage therapist and aspiring novelist. Connect with her at LinkedIn.

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