Health and happiness is all down to a roll in the dirt

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Health and happiness is all down to a roll in the dirtApril 1, 2007http://www.timesonline.co.uk/tol/life_and_style/health/article1596735.eceFORGET the spring-cleaning. A study has found evidence that bacteria commonin soil and dirt could improve people's spirits.According to the research, the action of Mycobacterium vaccae (M vaccae) onthe brain is similar to that of some commonly used antidepressants.The bacterium, which is related to the microbe that causes tuberculosis,appears to work by stimulating the body's immune system. This, in turn,prompts certain cells in the brain to produce more serotonin, a hormoneassociated with feelings of wellbeing."These studies help us to understand how the body communicates with thebrain and why a healthy immune system is important for maintaining mentalhealth," said Dr Chris Lowry, a neuroscientist at Bristol University whocarried out the research."They also leave us wondering if we shouldn't all spend more timeplaying in the dirt."The finding follows separate research by other scientists into the impactof bringing children up in "overhygienic" conditions.They found evidence that exposure to a wide range of common microbes inearly life helped to promote healthy development of the immune system.Without such exposure, the immune system seems more likely to mistake thebody's own cells as invaders and launch attacks on them. This could beone of the mechanisms underlying the surge in conditions such as asthma andeczema.The research by Lowry and a team of 12 scientists at Bristol and UniversityCollege London (UCL) takes this "hygiene hypothesis" a step further bylinking exposure to the microbes found in dirt with good mental, as well asphysical, health.Interest in the project arose after human cancer patients being treatedwith M vaccae unexpectedly reported increases in their quality of life.This could have been caused by the microbe having indirectly activated thebrain cells that produce serotonin.The researchers injected some mice with the bacteria while others were madeto inhale it. They then analysed the blood and brains of the infected miceto see what effect the microbes might have had on their immune systems andon serotonin levels.Details will be published in Neuroscience, an academic journal, this week.The study is highly unlikely to lead to new therapies for depression in thenear future but it does build on the growing body of research showing theimportance of the human immune system in regulating even the subtlestaspects of health.There are a range of studies supporting the hygiene hypothesis and the ideathat exposure to microbes is good for long-term health.In families with several children, the youngest often has the leastallergies, most likely because it picks up the elder siblings' infectionsso activating the child's immune system.Graham Rook, a professor of immunology at UCL who worked with Lowry, hasalready published research into the link between exposure to microbes andsubsequent development of allergies.Rook and two of his co-researchers are also working with S R Pharma, acompany looking into whether M vaccae could become the basis of treatmentsfor conditions such as asthma.Rook believes that improved cleanliness may be a contributory factor indiseases such as asthma, eczema and hay fever, along with autoimmunediseases such as Type 1 diabetes and inflammatory bowel disorders such asCrohn's disease. He said: "We've known for a couple of decades nowthat a whole group of chronic inflammatory disorders are becoming muchcommoner in the rich developed world."The body's response to such inflammatory diseases is regulated by immunecells which, said Rook, need to encounter harmless bacteria early in lifein order to work out how to respond effectively to real threats.Without these encounters, he said, the regulatory cells can malfunction,leading to health problems.Mark Pepys, professor of medicine at UCL, said that there was "quite alot of evidence" to support the hygiene hypothesis but said he would becautious about extending the theory to mental wellbeing.