Scientists may be able to use the bacteria living in your baby’s poop to predict how he or she will perform on cognitive tests by age two, a new study suggests. Researchers took fecal samples from nearly 100 one-year-olds and found that those with less diverse microbiomes and higher levels of the bacterial genus Bacteroides had higher cognitive scores one year later.

“The big story here is that we’ve got one group of kids with a particular community of bacteria that’s performing better on these cognitive tests,” said Rebecca Knickmeyer of the University of North Carolina School of Medicine, in a statement. “This is the first time an association between microbial communities and cognitive development has been demonstrated in humans.”

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READ MORE: The Fatherly Guide to Poop, Diapers, and Potty Training

Researchers have known for some time that gut bacteria can influence how rodents perform on cognitive tests, but these findings had never been confirmed in humans. So Knickmeyer and colleagues analyzed fecal samples from 89 one-year-olds and determined which bacteria occupied their diapers. One year later, they ran cognitive tests and brain scans and found that the babies’ microbial communities had little effect on their brain volumes. But children with less diverse microbiomes, and a preponderance of Bacteroides, performed better on cognitive tests.

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The findings raise as many questions as they answer. Are the bacteria actually communicating with the developing brain? “That’s something that we are working on now,” Knickmeyer said. “So we’re looking at some signaling pathways that might be involved.” The results are also a mixed bag, because prior studies have shown that kids with low microbial diversity (one of the key factors that this study links to higher cognitive scores) are also more likely to have asthma and diabetes. “Our work suggests that an ‘optimal’ microbiome for cognitive and psychiatric outcomes may be different than an ‘optimal’ microbiome for other outcomes,” Knickmeyer said.

There are several good reasons not to stock up on Bacterioids probiotics just because of this preliminary study. First of all, it’s still unclear whether this particular balance of bacteria causes higher cognitive scores, or whether it’s a symptom of a brain boost coming from elsewhere. Second of all, we still don’t know how low bacterial diversity affects children—perhaps they’ll grow up to be smart, but unhealthy. Finally, it’s always possible that a subsequent study with a larger sample size will fail to confirm any link between gut bacteria and brain power.

“It’s the very first step,” said coauthor Alexander Carlson, also of North Chapel Hill. “We’re not really at the point where we can say, ‘Let’s give everyone a certain probiotic.’ But we did have a few big takeaways from what we found. One was that, when measuring the microbiome at age one, we already see the emergence of adult-like gut microbiome communities—which means that the ideal time for intervention would be before age one.”

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