Who could have thought that the popular phrase “trust your gut” would become a trending wellness tip? After all, the state of our gut helps determine how we feel mentally and physically most days. When your gut bacteria are in balance, your body has a thriving population of beneficial bacteria that supports your immune system.
On the other hand, when the gut is not happy, immune imbalance, weight fluctuations, and digestive issues naturally happen along with other undesirable symptoms, including occasional gas, stomach upset, constipation, bloating, mood and sleep disturbances, and food sensitivities.
A new study, which was published in the journal Cell Host and Microbe, reveals that happiness may be the solution to protect the body from gastrointestinal problems. Authors Aman Kumar from UT Southwestern Medical Center’s Department of Microbiology and colleagues explained that the gut-brain axis (GBA), a bidirectional link between the central nervous system and the enteric nervous system of the body, is crucial to the microbial-host interactions or how microbes sustain themselves within the host organisms on an organismal, cellular, molecular, and population level.
Serotonin’s role in decreasing virulence gene expression
The researchers found that serotonin, the “happy chemical” that produces feelings of happiness and well-being in the brain, can reduce the ability of intestinal pathogens to cause deadly infections. They noted that the majority of studies on serotonin focuses on its effects on the brain. Yet, about 90% of this neurotransmitter – body’s chemical messengers – is produced in the gastrointestinal tract.
UT Southwestern Medical Center’s professor of microbiology and biochemistry Vanessa Sperandio said via Medical Xpress that in humans, trillions of bacteria live in the gut and most of these bacteria are beneficial. Yet, pathogenic bacteria may also colonize the gut and when they do, they are capable of causing disease and fatal infections in the body.
Sperandio, together with Kumar, laboratory manager Regan Russel and other colleagues recognized the fact that gut bacteria are affected by their environment. They wondered whether the happy chemicals produced in the gut could also affect the virulence of pathogenic bacteria that infect the GI.
For their study, the team worked with Escherichia coli O157, an enterohemorrhagic bacterial strain or bacterial species that causes a periodic outbreak of deadly foodborne infection. They grew these pathogenic bacteria in petri dishes (laboratory glassware) and exposed them to serotonin. Gene expression tests were then conducted and results show that that serotonin reduced the expression of genes that the pathogenic bacteria use to cause infection.
Experiments using human cells
For their additional experiments, the team used human cells and they found that the pathogenic bacteria cannot cause infection-associated damage in the cells when exposed to serotonin. For their next step, the team wanted to know if serotonin can still affect the virulence in a living host. So, they used mice in the lab.
As an analog to E.coli in humans, the researchers studied how serotonin could change the ability of Citrobacter rodentium (mouse gut bacterium). The genes of the mice were modified to either over- or underproduce serotonin in their GI. The team discovered that those who overproduced serotonin had gut bacteria that was were less likely to be colonized after being exposed or there was only relatively minor illness. Those that overproduced serotonin were treated with fluoxetine, a drug known as a selective serotonin reuptake inhibitor used to treat depression. On the other hand, mice that underproduced serotonin became sicker after being exposed to the bacteria, often dying because of the illness.
Sperandio and the team are planning to study the feasibility of manipulating the levels of serotonin. Currently, there are only a few available antibiotics that can effectively fight E. coli O157 and some antibiotics may cause the bacteria to release more damaging toxins, worsening the consequences of the infection. Sperandio said that it can be “very difficult” to treat bacterial infections, particularly in the gut. If Prozac fluoxetine or other drugs of the same class could be repurposed, it would serve as a new weapon to fight said infections, she added.
Dysbiosis: microbial imbalance
Dysbiosis is a condition in which gut bacteria become imbalanced, leading to a wide range of digestive disturbances. According to Healthline, dysbiosis is typically the result of a dietary change that increases the intake of protein, food additives, and sugar, an accidental chemical consumption, such as unwashed fruit or lingering pesticides, new medications that affect that gut flora, drinking two or more alcoholic beverages per day, unprotected sex that exposes the body to harmful bacteria, high levels of anxiety and stress, which weaken the immune system, and poor dental hygiene that allows the bacteria to grow out of balance in the mouth.
Prevalence of gastrointestinal conditions
Database company Statista surveyed 249,008 people in selected countries last year. Results show that some 19% of the adult population in Brazil and 10% in China had been diagnosed with a gastrointestinal condition. Other countries included in the list are Japan (9% of the adult population with the gastrointestinal condition), Russia (12%), United States (22%), and EU-5 (21%). The latter stands for European Union Five, which includes the UK, Spain, Italy, Germany, and France.
World happiness report
The 2019 World Happiness Report, a landmark survey of the state of global happiness that ranks 156 countries by how happy their citizens perceive themselves to be, found that negative feelings are rising globally. Residents rate on a scale of 0 to 10, from worst possible life to the best possible life.
The most satisfied country in 2019 was Finland (7.769) followed by Denmark (7.600), Norway (7.554), Iceland (7.494), Netherlands (7.488), Switzerland (7.480), Sweden (7.343), New Zealand (7.307), Canada (7.246), and Austria (7.246). The report likewise found happiness inequality – the psychological parallel to income inequality – has been rising within countries since 2007. This means that the gap between the unhappy and happy grew wider and the trend is strong in Sub-Saharan Africa, Asia, and Latin America.
The 2019 report also found that the US is particularly hard hit by the “epidemic of addictions,” including an addiction to technology that is blamed for the mental health trends among American adults. Researcher Jean Twenge argues in her report that screen time is displacing the activities that are key to our happiness, such as in-person social contact.
The findings of the UT Southwestern Medical Center team add up to the evidence that gut bacteria can indeed influence mood and microbiome and brain connection that may lead to novel therapies.