According to the Center for Disease Control (CDC), antidepressants are one of the most often prescribed medications. I have, for a long time, hypothesized that the reason so many people these days are unhappy is because we live our lives in a way that is un-natural to our bodies. Before modern day advancements, we would have been outside in the sun all day foraging, hunting, or gardening to survive. These activities would have included physical exertion no different than exercise and sun exposure, both of which have been linked to increased serotonin. Numerous studies have shown a decrease in the concentration of serotonin metabolites in the cerebrospinal fluid and brain tissue of people afflicted with depression. Whether the lack of serotonin metabolic activity is a side effect of depression or the cause, antidepressants work by inhibiting the re-uptake of serotonin in the synaptic cleft to enhance serotonin activity. Now gardening has been shown to increase serotonin as well via Mycobacterium vaccae. a harmless bacteria normally found in dirt.
Wednesday, 11 April 2007
by Michelle Carr
Mycobacterium vaccae, a harmless bacteria normally found in dirt, has been found to stimulate the immune system of mice and boost the production of serotonin, a mood-regulating brain chemical.
The bacterium has already been successfully used in people as a vaccine against tuberculosis. It is also being tested as a treatment for cancer patients and in asthma sufferers, as a way to control the allergic reaction and help ‘rebalance’ the immune system.
Now, studies on mice led by neuroscientist Christopher Lowry at the University of Bristol in England, suggests that the bacteria may have other applications as a treatment for mood disorders like depression.
“These studies help us understand how the body communicates with the brain and why a healthy immune system is important for maintaining mental health. They also leave us wondering if we shouldn’t all spend more time playing in the dirt,” said Lowry.
Interest in the unusual antidepressant properties of M.vaccae arose by accident following an experimental treatment for human lung cancer led by cancer researcher Mary O’Brien at the Royal Marsden Hospital in London, England. Under that treatment, patients received heat-killed inoculations of the bacteria.
Following the tests, O’Brien’s team observed not only fewer symptoms of cancer, but also improvements in their patients’ vitality, emotional health and mental abilities.
Lowry and his colleagues speculated that the bacteria in these earlier experiments might have activated brain cells to release mood-lifting chemicals. To investigate the idea further, they injected heat-killed bacteria into a group of mice and found that they initiated an immune response, which activated serotonin-producing neurons in the brain.
Low levels of serotonin cause depression – an illness which afflicts around 1.3 million Australians. The most commonly prescribed antidepressant medications help treat depression by delaying the re-uptake of serotonin, thus raising levels in the brain.
According to Lowry, the strange effect of the bacteria may work by prompting the body’s immune cells to release cytokines, chemicals known to activate sensory nerves that stimulate the brain. The findings are published in the journal Neuroscience.
“We believe that the brain then responds by activating serotonin neurons,” he said. “These studies help us understand how the body communicates with the brain and why a healthy immune system is important for maintaining mental health.”
They also raise the question of whether exposure to common bacteria from a young age, could make us less vulnerable to disease. “We believe that prolonged exposure to [M.vaccae] from childhood could have a beneficial effect,” said Lowry.
Further studies are required to confirm the effect in people and to see if other types of bacteria might have a similar effect, he said.
The study lends further support the ‘hygiene hypothesis’ whereby exposure to bacteria and pathogens from an early age helps balance the immune system. The idea is that some experience of disease early in life prevents our immune systems from attacking our own bodies – leading to allergies, asthma and other so-called auto-immune diseases.
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