In this article, we talk about the links between your gut and brain. We’ll also discuss a recent study asking whether your gut microbiome influences intelligence. Spoiler alert: It might.
As you read this sentence, billions of bacteria are working away in your gut. Collectively known as the gut microbiome, these tiny organisms are essential for good health.
Although researchers are still working to understand the precise links between gut bacteria and health, one thing is now clear: We need a thriving gut microbiome to ensure good health.
For instance, ZOE scientists run the largest ongoing investigation of diet, nutrition, and the gut microbiome. They have identified 15 “good” bacteria associated with positive health markers and 15 “bad” bacteria associated with poor health markers.
If you’d like to learn more about the microbes in your gut, get started by taking our free quiz today.
As scientists continue to study the gut microbiome, they are uncovering connections between our resident bacteria and a range of health conditions, including hypertension, diabetes, obesity, and heart disease.
A few decades ago, associations between chronic diseases and gut bacteria might have seemed unlikely. Now, they are widely accepted.
Some researchers are now focusing on a more surprising interaction: how our gut microbiome might influence our brain.
How can gut bacteria influence the brain?
It’s tempting to think of our brain as separate from the rest of our organs — a higher power, sat detached from the mayhem of the body. However, to control your body and understand what’s happening within it, your brain must be intimately attached to the rest of you.
The so-called gut-brain axis connects your gut and brain, allowing a two-way conversation.
Part of this connection is formed by the vagus nerve, which runs between the brain and gut. It plays a role in several important functions, including digestion, mood, and the immune response.
And as the importance of the gut microbiome has become increasingly clear, scientists sometimes call this system the microbiota-gut-brain axis.
The gut microbiome can influence your brain in a number of ways. One of these ways is through neurotransmitters — chemicals that nerves use to communicate.
For instance, some gut bacteria can influence whether certain neurotransmitters are produced, and others can directly produce neurotransmitters.
Gut bacteria can also trigger the release of immune chemicals called cytokines. These small proteins can either increase or reduce levels of inflammation, which directly impact your brain.
One of the latest studies into the relationship between your gut and brain asks whether the gut microbiome might, in some way, affect intelligence. The results appear in the journal Gut Pathogens.
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The gut microbiome and intelligence
Some scientists have already hunted for links between gut bacteria and intelligence, but the results have been inconsistent.
For instance, one study in older adults without any major health conditions found no association between gut bacteria and thinking skills, or cognitive ability. In contrast, another study with older adults in Japan did find an association between one particular type of bacteria and mild cognitive impairment.
The authors of the recent study decided to take a fresh look. Specifically, they focused on young healthy adults. Much of the previous research has focused on children, people in midlife, or older adults.
According to the scientists, young adults might provide an important window into the future because “cognitive health in young adulthood positively correlates with memory and brain functioning in later life.”
In all, the scientists used data from 40 people with an average age of 26. Around two-thirds of the participants were female.
The study focused on fluid intelligence, which the authors define as the “ability to process and learn new information, solve problems, and attend to and manipulate one’s environment.”
To test their cognitive abilities, participants underwent a computer-based test at home.
What did they find?
The scientists did identify a relationship between certain gut microbiomes and better scores on the cognitive tests.
This “Ruminococcaceae- and Coriobacteriaceae-dominated gut microbiome” included these species:
Eubacterium hallii group
Erysipelotrichaceae incertae sedis
Eubacterium nodatum group
Bacteroidales S24-7 group
Speaking about the results of the study, Prof. Tim Spector — ZOE’s Scientific Co-Founder and a professor of genetic epidemiology at King’s College London — said:
“This is a small study that suggests a link between certain microbes and intelligence. While it needs replicating in bigger numbers, it shows the massive potential of diet to influence our brains via our microbes.” — Prof. Tim Spector
One of ZOE’s nutrition scientists, Emily Leeming, a registered dietician, agreed: “The connection between our gut microbiota and our brain is an exciting new area of research. This study suggests that bacterial groups Ruminococcaceae and Coriobacteriaceace may play a role in cognitive performance supporting previous research in this area.”
“However,” Leeming continued, “we don't know if this is a cause-and-effect relationship. While this is an interesting finding, more studies are needed with a larger number of participants for us to understand more."
If you’re interested in knowing what species of bacteria live in your gut, ZOE can help. After taking our at-home test, you’ll get a breakdown of the microbes that make up your unique gut microbiome. We’ll also tell you the prevalence of the 15 “good” and 15 “bad” bugs.
Additionally, you’ll get a list of personalized gut-boosting foods that could support your gut health.
Evidence from previous studies
As Leeming mentioned, the current study is relatively small, but the results do match up with some earlier findings.
One study in older adults, for instance, found an association between Ruminococcaceae and good cognition.
Similarly, in another study on probiotics, the researchers found that participants with raised levels of Ruminococcaceae were protected from the negative effects of stress on memory.
As for Coriobacteriaceae, a study including participants with obesity found that the presence of these bacteria correlated with better processing speed and mental flexibility.
Scientists have also found links between some of the other bacteria in Ruminococcaceae- and Coriobacteriaceae-dominated gut microbiomes and changes in cognition.
According to the authors, earlier studies found links between Erysipelotrichaceae incertae sedis and improved cognitive performance and links between Eubacterium hallii group and social cognition. Social cognition describes how we remember and use information about other people.
Additionally, a study that involved 20 healthy participants identified other links between Lactococcus and the way we think. The researchers investigated a probiotic containing seven species of bacteria, including five species from the Lactococcus family.
The scientists found that those who took the probiotic showed less cognitive reactivity. This means that they were less likely to develop negative thought patterns when the researchers put them in a “sad mood.” The term “gut feeling” might be closer to the mark than we thought.
Although not directly related to intelligence, this is further evidence that Lactococcus might be able to influence the way you think.
How can we explain this?
As we mentioned earlier in the article, gut bacteria can communicate with the brain in several ways. One of these ways is by influencing levels of neurotransmitters.
Scientists have already shown that some of the bacteria in the Ruminococcaceae- and Coriobacteriaceae-dominated gut microbiomes can impact these chemical messengers.
For instance, the authors write that Lactococcus and Pseudomonas influence levels of the neurotransmitter serotonin. Serotonin is involved in many functions, including thinking, learning, and memory. Akkermansia — another bacterium from Ruminococcaceae- and Coriobacteriaceae-dominated gut microbiome — may also produce serotonin.
Also, Pseudomonas can affect levels of the neurotransmitter GABA. Lactococcus, the authors write, also produces the neurotransmitter dopamine and histamine, both of which can influence cognitive functions.
Although the results are intriguing, the study does have certain limitations. Importantly, there were only 40 participants in the trial. As a result, scientists will need to carry out more extensive studies to replicate the findings.
Also, the study is observational. In other words, the scientists could identify certain gut bacteria that are linked to intelligence test scores, but this does not mean that those bacteria caused the improvements in intelligence.
The authors explain that other factors could have influenced their results, including genetics, socioeconomic status, stool consistency, and measures of brain health.
If you would like to learn more about your personal gut microbiome and get insights into how different foods affect your blood sugar and blood fat levels, take our free quiz today.
With ZOE’s help, you can better understand the foods that boost your gut bacteria and help support your overall health.
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