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New Studies Show Strong
Link
Between Diet and Behavior
Can the right diet make a child less hyperactive, alleviate
an adult's depression, or even reduce aggression and antisocial acts?
Recent research offers surprising evidence about the value
of nutritional interventions for a wide range of behavioral and mood disorders.
Diet and childhood behavior
Researchers in the 1970s questioned the connection between
diet and behavior. Newer, more sophisticated studies, however, reveal that for
many children, the food/behavior link is real.
J. Breakey reviewed studies on food and behavior conducted
between 1985 and 1995, and concludes that the results "clearly show a
relationship" between what children eat and how they act. "The most
important finding," she says, "was that in almost all studies there
was a statistically significant change in behavior with dietary
intervention." In addition, the studies revealed a continuum of responses
to dietary interventions, "rather than the all-or-nothing earlier
expectation."
Although diet changes reportedly can improve a wide range
of behavior problems, including hyperactivity and sleep problems, Breakey says
"an important unexpected finding is the number of researchers who emphasize
that the symptom most affected by diet is mood, especially irritability."
Diet and aggression
While most studies on diet and behavior have focused
on reducing hyperactivity, there is evidence that diet also has a strong
influence on aggression. Physician Melvyn Werbach cites some examples:
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One study found that 20 subjects with marginal
deficiencies of thiamin were impulsive, highly irritable, aggressive, and
sensitive to criticism. After their diets were supplemented with thiamin,
the subjects' behavior improved significantly.
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Research shows that among adolescent males, iron
deficiency is directly associated with aggressive behavior. Furthermore, one
study found that iron deficiency was nearly twice as prevalent in a group of
incarcerated adolescents as among their non- incarcerated peers. Werbach
says animal studies indicate that iron deficiency may cause behavioral
impairment by diminishing dopamine transmission.
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Studies show that rats fed diets depleted in the amino
acid tryptophan become more aggressive toward mice. In addition, research on
vervet monkeys found that tryptophan-free diets increased aggression in
males, while high-tryptophan food reduced aggression in both males and
females.
These findings are not surprising, according to
Werbach, because tryptophan is the dietary building block of the brain chemical
serotonin, and low levels of this neurotransmitter are strongly linked to
behavior problems including impulsive aggression (See related article, Crime
Times, 1995, Vol. 1, No. 1-2, Page 7).
While noting that too little scientific research is
available on the diet/aggression connection, Werbach concludes,
"Epidemiological studies have repeatedly found associations between
overaggressive behaviors and deficiencies of several essential nutrients:
niacin, pantothenic acid, thiamin, vitamin B6, vitamin C, iron, magnesium and
tryptophan." This evidence, he says, "argue[s] that a nutritional
approach should be considered in the treatment of the aggressive behavioral
syndrome."
Diet and mood
Depression, a serious problem in and of itself, is a
risk factor for aggression and possibly even for criminal behavior (See related
article, Crime Times, 1997, Vol. 3, No. 4, Page 6). Recent research points to a
strong link between depression and dietary deficiencies, and in particular
deficiencies of the B vitamin folate (folic acid).
Beginning in the 1980s, study after study has shown
that low levels of folic acid are correlated with depression. Jonathan E. Alpert
and Maurizio Fava recently noted that "depressive symptoms are the most
common neuropsychiatric manifestation of folate deficiency," and that as
many as one third of adults diagnosed with depressive disorders have deficient
or borderline blood levels of folate. Studies by Alpert and Fava, as well as
other researchers, also suggest that depressed patients with low folate levels
respond poorly to antidepressant treatment, compared to subjects with normal
folate levels.
T. M. Ortega and colleagues say that the relationship
between depression and low folate levels is easily explained, "because of
the role of folates in [the] synthesis of neurotransmitters and elements of
neuron structure."
Another nutrient linked strongly to mood is selenium.
British researchers David Benton and Richard Cook first reported, in 1991, that
in normal subjects, higher selenium intake is "associated with a general
elevation of mood and in particular, a decrease in anxiety." The lower the
level of selenium in their subjects' diets, Benton and Cook reported, "the
more reports of anxiety, depression, and tiredness," all of which decreased
following five weeks of selenium supplementation.
Wayne C. Hawkes and Linda Hornbostel recently
conducted a similar experiment in the U.S., studying the effects of selenium
supplementation or depletion on 11 healthy men. "Adding more selenium to
the diets of our. volunteers had no effect on mood," they say, apparently
because the U.S. subjects began with higher selenium levels than the British
subjects. "However," the researchers say, "we did find that
taking most of the selenium out of our volunteers' diets worsened the moods of
those volunteers who had been consuming the lowest amounts of selenium prior to
the beginning of our study. This was similar to the British study where they
found that the moods of the people who ate the least selenium were improved most
by giving them more selenium."
Low levels of tryptophan also may lead to depression.
In 1997, K. A. Smith et al. studied 15 women who had experienced major
depression in the past but were no longer taking antidepressants. The subjects
drank either an amino acid mixture containing tryptophan, or the same mixture
without the tryptophan, and their depressive symptoms were measured before and
seven hours after drinking the substances. "The tryptophan-free mixture
produced a 75% reduction in plasma tryptophan concentration," the
researchers report. "After drinking [this] mixture, ten of the 15 women
experienced temporary but clinically significant depressive symptoms." No
mood changes were seen when patients drank the mixture containing tryptophan.
Diet and criminality
In addition to influencing mood, aggression, and
symptoms of hyperactivity, diet appears to significantly improve the IQs of some
children (See related article, Crime Times, 1996, Vol. 2, No. 2, Page 4). Since
hyperactivity, hyperaggressiveness, depression, and IQ all are associated with
criminality, some researchers are investigating whether or not diet may be
useful in treating criminals (and, in particular, young delinquents). To date
the research, while sparse, is encouraging.
During the early 1980s, Stephen Shoenthaler
instituted dietary changes in a dozen juvenile correctional institutions. His
data showed that following these dietary interventions, which involved 8076
delinquents, the institutions had a 47% reduction in antisocial behavior
including assaults, insubordination, horseplay, suicide attempts, and general
rule violations. Schoenthaler notes, additionally, that "the more violent
the bad behavior [before dietary interventions began], the more the
improvement."
In a typical study, Schoenthaler supplemented the
diets of 71 residents of a state juvenile treatment facility. During the
treatment phase of the double-blind, placebo-controlled, crossover study,
Schoenthaler reported, "overall violence fell 66 percent from 306 incidents
to 104. Total AWOL and escape attempts fell 84 percent from 79 to 13 incidents
and destruction or theft of state property dropped 51 percent from 49 to 24
incidents." He concludes that "the trial demonstrated, rather
convincingly, that supplementation at dose levels which pose no risk whatsoever
can produce a significant reduction in violence and antisocial behavior in
incarcerated juveniles."
Preliminary results from current studies by Schoenthaler
corroborate these earlier findings.
Needed: more data
Researchers investigating dietary interventions for
behavior- disordered children, troubled teens, and antisocial adults are excited
about the accumulating evidence showing that these simple measures may have
profound impact, but they are also frustrated by a lack of interest on the part
of most clinicians.
"Unfortunately, the idea that disturbed behavior
and crime in particular are essentially the result of adverse social factors is
so deeply embedded in human society that those seeking to conduct studies of
non-social factors such as defective diets usually find that they face an uphill
task," researcher Derek Bryce-Smith recently commented. "The
demonstrated links between diet and behavior badly need to be extended as a
matter of urgency, and their importance recognized."
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"The role of diet and behaviour in
childhood," J. Breakey, Journal of Paediatr. Child Health, 33, 1997,
pp. 190-194. Address: J. Breakey, P.O. Box 8, Beachmere, QLD 4510,
Australia.
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"Nutritional influences on aggressive
behavior," Melvyn R. Werbach, Journal of Orthomolecular Medicine, Vol.
7, No. 1, 1995. Address not listed.
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"Nutrition and depression: the role of
folate," Jonathan E. Alpert and Maurizio Fava, Nutrition Review, May
1997, Vol. 55, No. 5, pp. 145-149. Correspondence: Maurizio Fava, fax
1-617-726- 7541.
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"The role of folates in the diverse
biochemical processes that control mental function," T. M. Ortega, P.
Andres, A. Lopez- Sobaler, A. Ortega, R. Redondo, A. Jimenez, and L. M.
Jimenez, Nutr Hosp, Vol. 9, No. 4, July 1994, pp. 251-256. Address not
listed.
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"Effects of dietary selenium on mood in healthy
men living in a metabolic research unit," W. C. Hawkes and L.
Hornbostel, Biological Psychiatry, Vol. 39, No. 2, January 15, 1996, pp.
121-128. Address not listed.
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"The impact of selenium supplementation on
mood," David Benton and Richard Cook, Biological Psychiatry, Vol. 29,
No. 11, June 1, 1991, pp. 1092-1098. Address not listed.
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"Relapse of depression after rapid depletion of
tryptophan," K. A. Smith, C. G. Fairburn, and P.J. Cowen, The Lancet,
Vol. 349, No. 9056, March 29, 1997, pp. 915-919. Address not listed.
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"Abstracts of early papers on the effects of
vitamin and mineral supplementation on I.Q. and behaviour," Stephen J.
Schoenthaler, Personal and Individual Differences, Vol. 12, No. 4, 1991, pp.
335-341. (Additional information from personal communication.)
"Crime and nourishment," Derek Bryce-Smith,
Perspectives, March 15, 1996. Address not listed.
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