Probiotics on the brain
"Dr. James Greenblatt, chief medical officer of Walden Behavioral Care in
Waltham, is a proponent of probiotics...'Thank you, youíve never even met me and
yet youíve changed my life.' That was the sign-off in an e-mail from a man named
Mike that arrived at the office of Dr. James Greenblatt, a psychiatrist and the
chief medical officer of
Walden Behavioral Care in Waltham, on July 24. Greenblatt is not unused to
such effusive gratitude, but usually it comes from his patients.
Mike, though, lives in Colorado, where he had read an article online about how
Greenblatt had treated a young woman with severe obsessive-compulsive
disorder using traditional psychotherapy and medication coupled, less
traditionally, with probiotics, capsules filled with live 'good' bacteria.
Within 6 months, her symptoms were gone.
Mike also had issues with anxiety, heíd started obsessively pulling his hair
out 15 years earlier, but no one had been able to help him. Mike began treating
himself by taking the strongest over-the-counter probiotics he could find and
after a couple months, he noticed the urge to pull had disappeared. 'IT WORKED.'
Mike later wrote in a blog post.
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The idea that microbes in the body can affect the brain has gone in and out of
In 1896, physicians writing in Scientific American concluded, in the
language of the day, that 'certain forms of insanity' could be caused by
infectious agents 'similar to typhoid, diphtheria and others.' But after
Freudian psychoanalysis became popular in the 1st half of the 20th century, the
microbial theory of mental illness was largely forgotten, and stayed that way
Today, however, scientists know that trillions of micro-organisms live in your
digestive system, where they outnumber your human cells many times over and may
make up as much as 3% of your body weight. The evidence that these bacteria
affect a dense network of neurons in your gut, often called the '2nd brain', is
vast and growing.
In recent years, a microbial imbalance in the gut (called 'dysbiosis') has been
associated with chronic fatigue, obesity, certain types of cancer, and other
Itís unclear exactly how or which bacteria cause or cure which disorders and in
what complex ways, Greenblatt says, 'but the research is quite clear that the GI
tract affects brain health.' In this case, he says, '1+1 does equal 2.'
Research on the microbiome got a kick-start with the emergence of new methods of
DNA profiling that allowed doctors to quickly identify various species of
bacteria. Now, studies exploring how gut flora may affect health are exploding
onto the scene. Once considered 'alternative', maybe even a bit wacky, the field
is becoming firmly entrenched in the medical establishment: In 2007, the
National Institutes of Health earmarked $115 million for the 1st phase of the
Human Microbiome Project, which brings together researchers from several
institutions, including the
Broad Institute in Cambridge, and aims to map the ecology of the gut. In
late September, Harvard Medical Schoolís Division of Nutrition hosted a
symposium in Boston called ďGut
Microbiota, Probiotics and Their Impact Throughout the Lifespan.Ē It was so
popular, there was a wait-list to get in.
All the interest marks a fundamental change in the way scientists and medical
professionals view the connection between the brain and the gut. Not that long
ago, many doctors believed that the brain was essentially walled off from the
rest of the body and protected from infection. 'The dogma when I was in grad
school was that nothing crosses the blood-brain barrier,' says Nancy Desmond,
chief of the neuroendocrinology and neuroimmunology program at the National
Institute of Mental Health. 'But there are data now that punch holes in that
dogma.' The challenge, she says, 'is to try to get at the mechanisms that
underlie this apparent communication between microbiota in the gut and brain
function that is relevant to mental health.'
Possible pathways include the vagus nerve, which runs throughout the body, the
spinal cord, and numerous immune and endocrine mechanisms. For example, a
chemical in urine called HPHPA signals a buildup of dopamine in the brain, which
in turn 'strongly correlates with psychiatric symptoms,' according to Greenblatt,
'from anxiety to agitation.'
As in irritable bowel syndrome, the culprits here are species of the Clostridium
bacteria. Fighting them with targeted antibiotics, along with high doses of
probiotics, appears to help ease or eliminate symptoms.
Dr. Kyle Williams, director of the
Pediatric Neuropsychiatry and Immunology Program at Massachusetts General
Hospital, is also looking at how the microbiome influences the brain and
behavior. But Williams cautions that the bodyís ecosystem is incredibly complex
and that the placebo effect, patients feeling better even if the treatment isnít
actually doing anything,can be very strong in psychiatry. 'Thereís a lot of
excitement about the microbiome now,' he says, 'but evidence is what helps us
transform an exciting idea into therapies. Itís true the blood-brain barrier
isnít the impenetrable fortress we thought it was, but weíre learning more each
day about how molecules traffic or are transported across it.'
Though much remains to be learned, many physicians and researchers believe
thereís no harm in probiotics, as long as patients donít forgo conventional
medicines and treatments in their favor (where proven benefits are
greater than negative side effects). 'Whenever someone says thereís an
impossibility in medicine,' says Williams, 'they end up being corrected in a few