Should we feed our children bacteria?

Probiotics may be a promising avenue for promoting brain development and boosting learning
Chris Wood and Nicola Fawcett, Modernising Medical Microbiology, CC BY NC-SA 4.0
Chris Wood & Nicola Fawcett, Modernising Medical Microbiology, CC BY NC-SA 4.0

In recent years, scientists have been buzzing with excitement about the diverse roles of the human gut microbiome. They have discovered that the microorganisms in our gut can do much more than simply aid in digestion. Indeed, the “gut microbiota,” composed mostly of bacteria, can even influence emotions and cognition, a finding that has sparked a great deal of interest.

Studies in animals have shown a causal relationship between the gut microbiota and anxiety and social behavior, as well as higher cognitive skills such as memory. Studies in the emerging field that is examining the microbiota-gut-brain axis in humans show similar relationships. The microbiota has been associated with anxiety, depression, and stress, as well as cognitive function and brain activity. Some researchers think it may also play an important role in the development of psychopathologies, such as autism.

This new research field has given new meaning to the Latin phrase “Mens sana in corpore sano.” Apparently it is not enough to keep our bodies healthy if we want to have a healthy brain; we also need to take care of the millions of bacteria that inhabit our gut.

How do our gut bacteria relate to learning and education?

Children are born with a virtually sterile intestinal tract, but bacteria rapidly start colonizing the gut. The most significant development of the microbiota takes place during the first months of life, while development becomes more stable in the toddler years and beyond. Just as early life is a sensitive period for microbiota development, it is also a critical neurodevelopmental window, during which the foundations for a healthy, well-functioning brain are laid.

Effects of the gut microbiota on the brain might be expected to be larger during early development, because this is a time when the areas of the brain associated with higher order cognitive skills, such as the frontal cortex, are still developing. Indeed, a first study by Carlson and colleagues showed associations between infant gut microbiota and cognitive functioning at age 2.

Nonetheless, given the protracted development of the human brain and the lengthy period of intense learning that characterizes human development, the gut microbiota probably continue to play a role in brain functioning, cognitive development, and learning capacities throughout childhood.

“Apparently it is not enough to keep our bodies healthy if we want to have a healthy brain; we also need to take care of the millions of bacteria that inhabit our gut.”

Probiotics as an opportunity to “get it right”

There is growing evidence that the gut microbiota play a large role in brain development, and hence in learning and education. We should therefore strive to help children acquire and maintain a healthy gut microbiota. One approach is to give children probiotics – live bacteria that are known to have a beneficial effect on health. Probiotic bacteria are thought to produce shifts in microbial composition, positively influencing the functioning of the intestinal ecosystem and thereby improving health.

In humans, probiotics have been found to have a positive impact on physical health, even in fragile preterm babies. For example, a recent meta-analysis showed beneficial effects of probiotics on the health of preterm babies in low- and medium-income countries. Effects of probiotics on emotions, mood, behavior, and cognition are less well established. In adults, probiotic trials appear to show mood improvement and reduced stress, with probiotics even affecting brain activity.

In children, probiotics have been associated with reduced crying in babies with colic, a lower risk of developing a neuropsychiatric disorder, and fewer symptoms in children with autism spectrum disorder. With the exception of the colic findings, however, these results are from small studies that need to be replicated.

“Even if the effects of probiotics on development are modest, they might still make a difference in children’s lives, especially in impoverished communities and countries.”

Probiotics for prevention in children?

Despite the paucity of relevant research in children, probiotics appear to be a promising avenue for influencing brain development and learning potential in a positive way. There are no significant safety concerns about their use in healthy children, and they are becoming increasingly affordable. And even if the effects of probiotics on development are modest, they might still make a difference in children’s lives, especially in impoverished communities and countries.

Nevertheless, much remains to be learned before probiotics can be universally recommended as preventive food supplements for children in the general population.

Challenges in probiotic research

There are still many unanswered questions about probiotics. For example, researchers have yet to determine the ideal effective dose, length of supplementation period, and age of consumption. Moreover, the human gut is estimated to house somewhere between 500-1000 species of bacteria. Probiotic formulations typically contain only a single species or a combination of a few species, and we are far from determining the ideal combination of species to be ingested.

Taking this one step further, future probiotic formulations might be tailored to individual differences – in genes or habitual diet, for example. Moreover, it would make sense to develop probiotics with bacteria that have central roles in the child’s gut and that have coevolved with the human species. To date, most probiotics include species that have been chosen for their stability and ease of industrial production; this may limit the scope of their beneficial effects.

“Future probiotic formulations might be tailored to individual differences – in genes or habitual diet, for example.”

Clever study designs may help us fill the gaps in our knowledge of this field. Ideally, studies seeking to identify the effects of probiotics on the general population should be relatively large, longitudinal, and multidisciplinary in nature.

Such studies can begin to shed light on the long-term causal effects of probiotics on the gut microbiota and on child health, cognition, and behavior. Only then, when we know more about the effects of probiotics on the microbiota-gut-brain axis, will we be able to translate that knowledge into solid policy recommendations.

 

References

Carlson AL, Xia K, Azcarate-Peril MA, Goldman BD, Ahn M, Styner MA, Thompson AL, Geng X, Gilmore JH, Knickmeyer RC (2018). Infant Gut Microbiome Associated With Cognitive Development. Biol Psychiatry, 83, 148-159. doi: 10.1016/j.biopsych.2017.06.021.

Cerdó T, Ruíz A, Suárez A, Campoy C (2017). Probiotic, Prebiotic, and Brain Development. Nutrients, 9(11). pii: E1247. doi: 10.3390/nu9111247.

de Weerth C. (2017) Do bacteria shape our development? Crosstalk between intestinal microbiota and HPA axis. Neurosci Biobehav Rev., 83, 458-471. doi: 10.1016/j.neubiorev.2017.09.016.

Deshpande G, Jape G, Rao S, Patole S (2017). Benefits of probiotics in preterm neonates in low-income and medium-income countries: a systematic review of randomised controlled trials. BMJ Open, 7(12):e017638. doi: 10.1136/bmjopen-2017-017638.

Pinto-Sanchez MI, Hall GB, Ghajar K, Nardelli A, Bolino C, Lau JT, Martin FP, Cominetti O, Welsh C, Rieder A, Traynor J, Gregory C, De Palma G, Pigrau M, Ford AC, Macri J, Berger B, Bergonzelli G, Surette MG, Collins SM, Moayyedi P, Bercik P (2017). Probiotic Bifidobacterium longum NCC3001 Reduces Depression Scores and Alters Brain Activity: A Pilot Study in Patients With Irritable Bowel Syndrome. Gastroenterology, 153(2):448-459.e8. doi: 10.1053/j.gastro.2017.05.003.

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van den Nieuwboer, M., Brummer, R. J., Guarner, F., Morelli, L., Cabana, M., & Claassen, E. (2015). Safety of probiotics and synbiotics in children under 18 years of age. Beneficial Microbes, 6, 615–630. https://doi.org/10.3920/bm2014.0157

van den Nieuwboer M, Claassen E, Morelli L, Guarner F, Brummer RJ (2014). Probiotic and synbiotic safety in infants under two years of age. Benef Microbes. https://doi.org/10.3920/BM2013.0046

 

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