- The chemical in turkey that may cause people to nod off
after Thanksgiving dinner also plays a role in maintaining good mood and
memory, especially among people with a family history of depression, says
new research published in the journal Brain, Behavior, and Immunity.
-
- Lead author Wim J. Riedel, Ph.D., and colleagues at the
Brain and Behavior Institute at the University of Maastricht in the Netherlands
examined the effects of the body's depletion of an amino acid called tryptophan
on mood and cognitive function. They also measured how long the effects
of the depletion lasted.
-
- Tryptophan, known for its presence in turkey and commonly
blamed in the media for creating the sluggish after-meal sensations experienced
by many Thanksgiving diners, is a metabolic precursor to the chemical messenger
known as serotonin. In addition to turkey, the chemical is found in foods
like milk, bread, cheese and bananas. Tryptophan depletion decreases serotonin
levels in the brain, which in turn can lead to depression and other problems.
While the study is not definitive and does not offer a solid conclusion
that eating more tryptophan will enhance memory or mood, it does indicate
a possible connection.
-
- "Experimental lowering of tryptophan, and hence
serotonin, appears to impair learning and memory and can cause depressed
mood, especially in people who have a family history of depression, Riedel
says."
-
- The experiments involved 27 volunteers, 16 of whom had
an immediate relative with major depression. Researchers lowered the level
of tryptophan in the volunteers' bodies, and memory tests showed impairment
in their ability to recall and recognize words they learned during, but
not before, the tryptophan depletion time period. However, the volunteers
did better on focused attention tasks, concentrated listening tasks and
tasks measuring the speed of memory retrieval.
-
- The results also showed that tryptophan depletion induced
mood depression in half of the subjects who had a family history of depression
but in only 9 percent of those with no family history of depression. The
latter finding suggests that people with depression in their families are
more vulnerable to changes in serotonin levels. The mood depression effects
ended within 24 hours in all of the volunteers, however.
-
- "These findings may have implications for people
who have a history of major depression in their families and people whose
tryptophan becomes depleted because of dieting," the authors note.
"They also may have implications for people whose tryptophan becomes
depleted because they are undergoing immunotherapy for cancer."
-
- The study was funded entirely by the Brain & Behavior
Institute of the University of Maastricht and the University Hospital Research
fund.
-
- Editor's Note: The original news release can be found
<http://www.cfah.org/hbns/news/chemical11-18-02.cfm>here.
-
- Note: This story has been adapted from a news release
issued for journalists and other members of the public. If you wish to
quote any part of this story, please credit Center For The Advancement
Of Health as the original source. You may also wish to include the following
link in any citation:
-
- http://www.sciencedaily.com/releases/2002/11/021119073229.htm
-
- <http://www.sciencedaily.com/copyright.htm>Copyright
© 1995-2002 ScienceDaily Magazine | Email: <mailto:editor@sciencedaily.com>editor@sciencedaily.com
-
- Comment
-
- From Mary Sparrowdancer
sparrowdancer1@earthlink.net
11-20-2
-
- Hi Jeff,
-
- I have some concerns about this article. While it states
that its study is "not definitive and does not offer a solid conclusion
that eating more tryptophan will enhance memory or mood," it also
states, "it does indicate a possible connection." Because people
might be tempted to purchase tryptophan due to this suggestion, it is perhaps
a good idea to provide some additional information.
-
- Not mentioned in the "possible connection"
between mood swings and tryptophan levels, is a key factor in the body's
natural conversion of tryptophan into other calming elements. The body
must first have adequate levels of vitamin B6 (as well as adequate magnesium)
for the upkeep of tryptophan and the conversion process. When there is
inadequate B6 in the body - and stress of any kind depletes the body of
its reserves of B-complex vitamins, including B6 - tryptophan forms a substance
known as "xanthurenic acid" (XA). It has been known for at least
fifty years that xanthurenic acid created by B6 depletion (and excreted
in the urine) is also associated with pancreatic damage that can result
in diabetes. More recent studies have found that XA is a possible necessary
link in the development of malaria. It has also been found to be associated
with cataracts, and is associated with anxiety and depression.
-
- It has been shown that giving additional tryptophan to
people already deficient in B6 creates further B6 depletion as measured
by XA excretion. I have long wondered if "a family history of depression"
might be symptomatic of a family in need of additional B6 in their diets.
-
- Caution should also be stressed regarding taking B6 -
or any of the B vitatims - alone. The B vitamins should always be taken
as a complex.
-
- Best to you, Mary Sparrowdancer
-
-
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