Omega-3
and Mental Depression
By
Morten Bryhn MD, Ph D
10/16/2001
Seasonal mood changes is common and possibly related to
reduced light exposure during winter time. Located at an
altitude of 64 degrees North the population of Iceland is
subjected to only limited hours of light during several
months per year. However, seasonal mood change is literally
absent in the Icelandic population.
Seasonal
mood changes is common and possibly related to reduced light
exposure during winter time. Located at an altitude of 64
degrees North the population of Iceland is subjected to
only limited hours of light during several months per year.
However, seasonal mood change is literally absent in the
Icelandic population. Scientists report that this may be
explained by their dietary habits with high intake of omega-3
fatty acids from fish (1).
Four 1000-person groups were randomly selected from the
Icelandic National Register. By mail each 1000 individuals
were sent a questionnaire during January, April, July, or
October designed to reveal depression and anxiety in. Interestingly
the scores for these symptoms did not differ between summer
and winter. This lack of seasonal anxiety and depression
is in sharp contrast to findings from similar studies in
other countries and may be explained by the Icelandic diet
with a high intake of omega-3 fatty acids from fish.
The
prevalence of major depression has increased and the age
of onset has decreased in every decade during the 2000 century
in the Western World. Concomitantly the intake of dietary
lipids has changed dramatically mainly by an increase in
the content of omega-6 oils from seeds and vegetables in
exchange for saturated fat and a reduction in the intake
of omega-3 fatty acids. Depressive patients are in fact
depleted in their content of omega-3 fatty acids in red
blood cells indicating that the content of these fatty acids
may be low even in the brain (2). However, populations with
a higher intake of fish containing omega-3 fatty acids seem
to differ significantly from this pattern. The dietary habits
in many Asian populations regarding seafood is very different
from in the US and interestingly the prevalence of depression
is much higher in large cities in the US compared with cities
in Asia (Fig. 1).
A population
study of 3 204 adults in Finland revealed that those with
frequent intake of fish were less susceptible to having
depressive symptoms compared to the group of infrequent
fish consumers (3). Along the same line a population study
from the US examining the prevalence of depression after
delivery demonstrated that low seafood consumption increased
the risk of having depression (4).
Intrigued
by the observations of a possible relation between the content
of omega-3 fatty acids from fish and the prevalence of mental
depression a study on patients with manic depressive disease
was performed in Boston, USA. These patients have repetitive
occurrence of severe mental depression which may be very
resistant to pharmacological therapy. Thirty patients were
randomly allocated to prophylactic treatment with omega-3
fatty acids or placebo. After 4 weeks the group getting
omega-3 fatty acids were doing significantly better compared
to those getting placebo regarding the occurrence of depressive
symptoms (5).
Omega-3
fatty acids are essential nutrients that have to be a part
of our daily diet. Low intake of these fatty acids has been
connected to a high risk of contracting cardio-vascular
disase and even Alzheimer's Dementia (6). At first sight
it may sound strange to tie reduced intake of a nutrient
to symptoms of brain malfunction. However, omega-3 fatty
acids exert a series of important biologic effects in different
parts of our body due to the fact that they are integrated
in the membrane of many different cells. As much as 60%
of the brain tissue contains fat analogues having not only
structural properties but takes place in the transduction
of signals over the cellular membrane. In the brain docosahexaenoic
acid (DHA) is the preferred omega-3 fatty acid. Integration
of DHA in the cell wall improves physical properties of
the cell membrane but does also actively participate in
the signal transduction which is the basal mechanism for
all brain functions including mental functions. There are
several chemical transmitter substances which are necessary
for normal brain activity. However, it seems that serotonin
is the neurotransmitter which is most closely related to
behavioural functions such as sleep, wakefulness and mood.
Animal experiments have shown that stimulation of certain
serotonin receptors lead to a release of DHA from the cellular
membrane. Important new anti-depresant pharmaceuticals such
as Prosac are acting on the serotonin system. It seems that
DHA acts as a so called second messager within the brain
cell actively participating in the processing and handling
of signals related to the serotonin system. DHA is therefore
probably important for the regulation of human behaviour.
The net effect of omega-3 fatty acids appear to be a general
dampening of overactive signal transduction.
Based
on the present findings it seems that omega-3 fatty acids
are important for brain functions connected to mood and
that winter depression may be prevented by increasing the
amount of these fatty acids in our diet by eating more fatty
fish or taking a food supplement containing omega-3 fatty
acids.
REFERENCES:
1) Magnusson A, Axelsson J, Karlsson MM, and Oskarsson H.
Lack of seasonal mood change in the Icelandic population:
Results of a cross-sectional study.
Am J Psychiatry 2000;157:234-238
2) Peet
M, Murphy B, Shay J, and Horrobin D. Depletion of omega-3
fatty acid levels in red blood cell membranes of depressive
patients.
Biol Psychiatry 1998;43:315-319
3) Tanskanen
A, Hibbeln JR, Tuomilehto J, et al. Fish consumption and
depressive symptoms in the general population in Finland
Psychiatric Services 2001;52:529-531
4) Hibbeln
JR. Seafood consumption, the DHA content of mother's milk
and prevalence rates of postpartum depression: a cross-national
ecological analysis
J of Affective Disorders; in press 2001
5) Stoll
AL, Locke CA, Marangell LB, and Severus WE. Omega-3 fatty
acids and bipolar disorders: a review
Prostaglandins, Leucotriens and Essential Fatty Acids 1999;60:329-337
6) Kalmijn
S, Launer LJ, Orr A et al. Dietary fat intake and the risk
of incident dementia in the Rotterdam Study
Ann Neurol 1997;42:776-782
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