| Omega-3s and Neuropsychiatric Disorders
Evidence is mounting that after several
generations of omega-3 deprivation, Americans’ overall health is deteriorating.
Depression, suicide, violence, and formerly rare and mysterious disorders,
such as autism, are becoming increasingly common. It is impossible to
quantify the exact effects of a simple but profound change in the
diet of an entire nation. But some scientists believe that a move
away from a balanced ratio of omega-6 to omega-3 fatty acids, which
began about a century ago, has affected us in ways we are only now
beginning to comprehend. And the changes have been anything but positive.
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Heart disease and cancer rank among our biggest killers. It is no coincidence
that most Americans consume far too few omega-3s, nor is it a coincidence that
omega-3 supplementation has been shown to improve cardiovascular health and
to inhibit certain types of cancers.37-39,44 Is
there a similar connection between simple diet and the rising incidence of
disorders such as dyslexia, ADHD, depression, schizophrenia, and autism?
Some scientists are convinced the answer is “yes.”
And speculation regarding omega-3s’ role in neurological health does
not end there. Experiments have shown that supplementation with the omega-3
fatty acid DHA increases the frequency of a particular type of brain wave that
is associated with memory and learning.42 Other studies have shown that infants
receiving adequate omega-3s develop visual acuity sooner and perform better
on intelligence tests than infants deprived of sufficient omega-3s.25-28 Omega-3s
are supplied naturally in breast milk, provided the mother’s intake of
omega-3s from plant or marine sources is adequate. But until recently, crucial
omega-3s were absent from commercial infant formulas. Even now, omega-3s are
only available in special, more expensive infant formulas.
Aversion to Fish
May Be Depressing
For several years, researchers have noted a correlation between
omega-3 deficits and severity of depression. Patients with the lowest
levels of essential omega-3 fatty acids tend to be the most severely
depressed, while healthy control subjects are more likely to have
normal levels of omega-3s, as measured in red blood cell membranes.17 In a recently published clinical paper, researchers in the Netherlands
reported that subjects with low levels of omega-3 fatty acids (and
high omega-6 to omega-3 ratios) were significantly more likely to
be depressed than those whose levels of omega-3s approached a more
balanced level. The study group consisted of more than 3,000 adults
over the age of 60, and inflammation and atherosclerosis were ruled
out as confounding factors. The finding, researchers noted, “suggests
a direct effect of fatty acid composition on mood.”15
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The relationship between mood and fatty acid composition in the body also has
been confirmed by research conducted in the U.S. by Andrew Stoll, M.D., Assistant
Professor of Psychiatry at Harvard Medical School and director of the Psychopharmacology
Research Laboratory at McLean Hospital in Belmont, MA. Dr. Stoll has focused
his extensive research efforts on depression (including post-partum depression)
and bipolar disorder (or manic-depressive illness). In numerous medical journal
articles and in his book The Omega-3 Connection, Dr. Stoll has documented impressive
results with omega-3 supplementation among patients ranging from those with
treatment-resistant major depression to post-partum depression and bipolar
disorder.16,18
Other researchers also have confirmed a definitive link between consumption
of omega-3s and mental health. Studies have examined either blood or adipose
tissue levels of omega-3s. They have consistently revealed a correlation between
low levels of omega-3s and depression.12 Omega-3 supplementation has proven
effective in the treatment of mild to moderate depression, or as an adjunct
to therapy with modern drugs, especially in bipolar disorder. But there appears
to be a point at which omega-3 supplementation is too little, too late. Supplementation
appears to be largely ineffective in cases of major depression.19 One small
but well-designed study found no significant benefit from treatment of major
depression with DHA versus placebo.20 Even in these cases, however, omega-3
supplementation may provide a boost to standard therapy, particularly in treatment-resistant
patients.21
As Dr. Stoll points out in The Omega-3 Connection, the link between omega-3s
and heart health is well established and fairly well known among the general
public. But research linking mood and omega-3s is relatively new, and much
remains to be explored. Some studies provide indirect evidence of the importance
of omega-3s to normal brain function, but definitive work remains to be done
before scientists and the public are likely to embrace the notion that something
as simple as changing dietary habits can affect so many lives, in so many
ways, so profoundly.
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The brain-health connection is hardly surprising, however—lipids are
integral to the structure and function of the brain, which comprises about
60% lipids (fat). What is surprising is that brain-lipid abnormalities are
only now receiving the close scrutiny they clearly deserve. The leukodystrophies,
for instance, represent an entire class of neurological disorders caused by
flaws in the fatty myelin sheath, which insulates a key component of nerve
cells and allows propagation of nerve signals. Some scientists are suggesting
that neuropsychiatric disorders such as dyspraxia (loss of coordination), autistic
spectrum disorders, ADHD, schizophrenia, and dyslexia – which often have
features that overlap one another – should be re-classified under the
blanket term phospholipid spectrum disorders. This new term recognizes the
underlying cellular lipid abnormalities that link these seemingly disparate
yet related disorders.22
In essence, phospholipid spectrum disorders are characterized by abnormalities
in the phospholipid and fatty acid composition of neural membranes. Cell membranes
play a crucial role in controlling the flow of chemicals and nutrients trafficking
between cells’ interiors and the outside. Cell membranes are largely
composed of lipids, so any abnormalities in those lipids may cause interruptions
in normal communication among neurons. Traditionally, scientists have sought
to improve communication by focusing on the neurotransmitters, which carry
messages from cell to cell. In the case of depression, for instance, it is
believed that symptoms arise when the normal flow of serotonin, a powerful
mood-regulating neurotransmitter, is interrupted.
Indeed, many groundbreaking therapies, including the new class of selective
serotonin reuptake inhibitors (SSRIs), such as Prozac® and Zoloft®,
have succeeded by enhancing the availability of one or more neurotransmitters.
But the newer, phospholipid-spectrum-disorders approach revisits the problem
by addressing underlying abnormalities in cell membranes. Because omega-3s
fill an invaluable niche in cellular membrane architecture, it follows that
correcting deficits in omega-3 supplies will improve cellular membrane function,
thus improving intercellular neurotransmitter transport and ultimately restoring
normal brain function.
Fish Oil: Protective Against Lung Disease?
Results from studies on
the use of fish oil in the treatment of chronic lung diseases—such
as emphysema, asthma, bronchitis, and the debilitating genetic disorder,
cystic fibrosis—have
been both tantalizing and inconclusive. Omega-3 supplementation in
diseased subjects has produced encouraging results overall, but there
are inconsistencies.
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One small study on cystic fibrosis patients found significant improvement,
especially decreased inflammation, among those receiving both DHA and EPA for
eight months. Patients receiving omega-3s required fewer antibiotics to control
chronic lung infections and did better on tests of lung capacity. Other researchers
have reported improvements in biochemical markers of disease, but little or
no evidence of clinical changes. In the case of asthma, research reveals more
improvement among children than adults, but further, larger studies would be
required to rule out chance. Trials on smokers have indicated that omega-3s
are protective against emphysema and chronic bronchitis, and yield an improvement
in spirometry values (a measure of lung capacity). Another trial found a correlation
between fish oil consumption and improvement in lung capacity even among non-smokers.43
After reviewing published evidence from around the world, Harvard researcher
Joel Schwartz concluded: “…a case can be made for why dietary
intakes of PUFAs [polyunsaturated fatty acids (including omega-3s)]…might
both be protective against lung disease and ameliorate the normal decline in
lung function with age.”40 Schwartz notes, however, that more research
is in order: “It is reasonable to study the relation between dietary
PUFAs and both lung disease and the normal aging process in the lung.”
Fish oil supplementation, then, holds promise not only as a health-improving
strategy for those with lung disease, but also as a hedge against the normal
effects of aging on the lungs of otherwise healthy individuals. As Schwartz
notes, “There is clear evidence of an effect of omega-3 fatty acids on
potential modulators of lung disease.”40 Clearly these intriguing results
warrant further investigation and provide another example of the unexpected
potential benefits of omega-3s.
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Thwarting Cancer with Omega-3s
Studies have shown that omega-3s can
slow the growth of experimentally induced cancerous tumors, improve
the effectiveness of chemotherapy, and reduce the side effects of
chemotherapy and cancer. Several mechanisms of action have been proposed
to explain these multiple benefits. Omega-3s may suppress nuclear
factor-kappaB activation and bcl-2 expression, allowing cancer cells
to self-destruct. Omega-3s may also decrease the rapid growth of
both cancer cells and the all-important blood supply that fuels the
cells’ unnaturally accelerated
growth, by suppressing the expression of cyclooxygenase-2 in tumors.
And omega-3s may interfere with the activity of two tumor-promoting
genes.
Perhaps most amazing of all, omega-3s may induce cancer cells to differentiate.
This is particularly significant, because cancer is a disease characterized
by otherwise ordinary cells run amok. Cancer cells are undifferentiated; instead
of behaving according to their specific identities (for example, a blood cell
behaves as a blood cell, not as a retinal cell), cancer cells “lose their
identity,” so to speak. Instead of performing specific duties and following
strict “rules” governing growth and dissemination, undifferentiated
cancer cells are interested in unbridled growth alone, to the detriment of
all else.
“It seems reasonable to assume that after appropriate cancer therapy, consumption
of omega-3 fatty acids might slow or stop the growth of metastatic cancer cells,
increase longevity of cancer patients, and improve their quality of life,” concluded
one team of researchers.44 Another team
noted: “There is both epidemiologic
and experimental evidence that the long-chain omega-3 fatty acids…exert
protective effects against some common cancers, notably those of breast, colon,
and, perhaps, prostate.”37 Other
researchers added skin cancer to the list, finding that DHA is more effective
at preventing skin cancer than EPA, and noting that a balanced ratio of dietary
omega-6 to omega-3 fatty acids may play an important role in this effect.45 As
in other areas of omega-3 research, more work needs to be done to further illuminate
the potential cancer-preventing properties of omega-3s.
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