When bacteria changes the way we behave

Bacteria in the gut produce vitamins and help break down our food. They do much more than that though. There are about ten times as many bacteria in the body as human cells. Our ecosystem of bacteria, called our microbiome, weigh about 3 kilograms and also vastly outweigh the number of genes we have. A new study has bolstered previous findings that certain bacteria can affect metabolic health and weight. Bacteria are also connected to inflammatory bowel disease and side effects from prescription drugs. Another new paper found that bacteria influences the way we feel, secreting chemicals involved with mood-regulation (an estimated 50 per cent of dopamine, for example, and the majority of serotonin are created in the gut). Bacteria are seen as so significant that scientists now believe that much of what makes us human is our microbiome. In fact we are, as scientists have come to say, more microbial than human. It stands to reason then that our bacteria might influence our behaviour. It is standing to science too. “You wouldn’t believe what we’re extracting out of poop,” Mark Lyte, a researcher in microbial endocrinology, tells New York Times Magazine. “We found that the guys here in the gut make neurochemicals. We didn’t know that. Now, if they make this stuff here, does it have an influence there? Guess what? We make the same stuff. Maybe all this communication has an influence on our behaviour.” To test this idea, Lyte, who was once called ‘crazy’ for his hypothesis, changed the diet of mice and, by doing so, appeared to improve their memory and learning. It provided some proof, he said, that diet can influence the bacterial balance and, as a result, behaviour. A second set of experiments, transferring bacteria between animals also affected behaviour. “If you transfer the microbiota from one animal to another, you can transfer the behaviour,” Lyte said. Promising as the research is, there is still a long way to go, says Sarah Dash, from Deakin University’s School of Medicine, whose research focus is the gut microbiome. “It’s important to remember that findings of animal research are not, of course, generalisable to human populations,” she says. “Humans are much more complex – both biologically and socially – than animals in a laboratory. However, the animal literature is exciting, and serves as justification to investigate this relationship in humans.” The problem with humans is that there isn’t a one-size fits all ecosystem of gut bacteria that equates to good health. “There’s no one ‘Gold Standard’ for what a healthy gut looks like,” Dash explains. “There’s great variability in what composes the gut microbiome from person to person, and each individual may have a ‘balanced bacterial signature’ that indicates a healthy gut, by their individual standards. ” This means that the proliferation of probiotics and gut-health supplements are premature. “It’s the Wild West out there,” Lyte said. “You can go online and buy any amount of probiotics for any number of conditions now, and my paper is one of those cited. I never said go out and take probiotics.” Dash agrees. “There’s still quite a bit of debate around the dose, frequency and strain of bacteria required to improve gut health, and at this point, there is no conclusive evidence that probiotics substantially influences the gut microbiota,” she says. “While there’s some evidence of its benefits, these effects are not likely to make substantial, lasting change to the core composition of the gut microbiota.” While the research, still in its embryonic stage, continues there are simple lifestyle choices we can make to create a healthy ecosystem for ourselves and our bacteria. “While much of the gut microbiota composition is determined by genetics and by factors in very early life, there are still strategies that research suggests could contribute to gut health and may, in turn, promote the health and protection of the brain,” Dash says. A varied, whole food diet composed of fruits, vegetables, and whole grains. “This dietary pattern has also been linked to higher levels of Bacteroidetes; a type of bacteria that are particularly good at producing short chain fatty acids, which help regulate gut inflammation,” Dash explains. “Eating non-digestible carbohydrates (eg, dietary fibre found in fruits, vegetables, and whole grains), secondary plant metabolites, such as flavonoids (found in brightly coloured fruits, vegetables, and red wine), and living micro-organisms known as ‘probiotics’ (found in such foods as yoghurt, kefir, and kimchi) may contribute to gut health,” Dash says. “Individuals who consume a Western style diet (highly processed, high fat/sugar foods) experience less of the protective benefits of plant foods and simultaneously provoke other metabolic disruptions through high fat and sugar consumption, which contribute to gut dysbiosis and inflammation.” Exercise. “Regular, moderate exercise may have a positive anti-inflammatory benefits, promote good gut health, and may increase levels of brain-protecting neurotrophins,” Dash explains.

The Age, 25 June 2015 ;http://www.theage.com.au ;