Post by David Dalton Post by David Dalton
Well, I eat yoghurt regularly.
and I haven't been on antibiotics recently
"Here I go again...back into the flame" (Sarah McLachlan)
14 December 2010
Diet shown to trigger mental illness
by Kate Melville
Changes in diet have previously been linked to a reduction of abnormal
behaviors in mentally ill animals and people, but a new Purdue
University study shows that diet can also trigger the onset of mental
illness in the first place.
In the experiment, mice were fed a diet high in sugar and tryptophan
(an essential amino acid) that was expected to reduce abnormal hair-
pulling. Instead, mice that were already ill worsened their hair-
pulling behavior and the seemingly healthy mice developed the same
"This strain of mouse is predisposed to being either a scratcher or a
hair-puller. Giving them this diet brought out those predispositions,"
said study author Joseph Garner, whose results were published in
Nutritional Neuroscience. "They're like genetically at-risk people."
Garner studies trichotillomania, an impulse-control disorder in which
people pull out their hair. The disorder, which disproportionately
occurs in women, is thought to affect between 2 - 4 percent of the
Mice that barber (pull their hair out) have been shown to have low
levels of serotonin activity in the brain. Serotonin is known to
affect mood and impulses. Garner hypothesized that increasing
serotonin activity in the brain might cure or reduce barbering and
Serotonin is manufactured in the brain from the amino acid tryptophan,
which is consumed in food. The problem is that tryptophan often
doesn't make it across the barrier between blood and the brain because
other amino acids can get through more easily and "block the door" for
Garner modified a mouse diet to increase simple carbohydrates, or
sugars, and tryptophan. The sugars trigger a release of insulin, which
causes muscles to absorb those other amino acids and gives tryptophan
a chance to make it to the brain. Using eight times as much sugar and
four times as much tryptophan, Garner observed a doubling of serotonin
activity in the brain. But the mice did not get better. "We put them
on this diet, and it made them much, much worse," Garner said.
A second experiment divided the mice into three groups: those that
were seemingly normal, others that had some hair loss due to barbering
and a group that had severe hair loss. All the mice soon got worse,
with conditions escalating over time. "Three-quarters of the mice that
were ostensibly healthy developed one of the behaviors after 12 weeks
on the new diet," Garner said.
Some of the mice also developed ulcerated dermatitis, a fatal skin
condition that was thought to be caused by an unidentified pathogen or
allergen. Garner saw that the only mice that contracted the condition
were the scratchers.
"What if ulcerated dermatitis, like skin-picking, another common
behavioral disorder, is not really a skin disease at all?" Garner
mused. "We now have evidence that it may be a behavioral disorder
When taken off the new diet, the negative behaviors stopped developing
in the mice. When control mice were switched to the new diet, they
started scratching and barbering.
The study raises questions of how diet might be affecting other
behavioral or mental illnesses such as autism, Tourette syndrome,
trichotillomania and skin-picking. He said that before now, a link
between diet and the onset of mental disorders hadn't been shown.
"What if the increase of simple sugars in the American diet is
contributing to the increase of these diseases?" Garner wonders.
"Because we fed the mice more tryptophan than in the typical human
diet, this experiment doesn't show that, but it certainly makes it a
possibility." Garner next wants to refine the experiments to better
imitate human dietary habits, including the amount of tryptophan
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Source: Purdue University
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