New study links DHA type of omega-3 to better nervous-system function

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New study links DHA type of omega-3 to better nervous-system function

http://www.eurekalert.org/pub_releases/2009-12/apa-nsl121609.php

WASHINGTON — The omega-3 essential fatty acids commonly found in fatty fish and

algae help animals avoid sensory overload, according to research published by

the American Psychological Association. The finding connects low omega-3s to the

information-processing problems found in people with schizophrenia; bipolar,

obsessive-compulsive, and attention-deficit hyperactivity disorders;

Huntington's disease; and other afflictions of the nervous system.

The study, reported in the journal Behavioral Neuroscience, provides more

evidence that fish is brain food. The key finding was that two omega-3 fatty

acids – docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) – appear to

be most useful in the nervous system, maybe by maintaining nerve-cell membranes.

" It is an uphill battle now to reverse the message that 'fats are bad,' and to

increase omega-3 fats in our diet, " said Norman Salem Jr., PhD, who led this

study at the Laboratory of Membrane Biochemistry and Biophysics at the National

Institute on Alcohol Abuse and Alcoholism.

The body cannot make these essential nutrients from scratch. It gets them by

metabolizing their precursor, á-linolenic acid (LNA), or from foods or dietary

supplements with DHA and EPA in a readily usable form. " Humans can convert less

than one percent of the precursor into DHA, making DHA an essential nutrient in

the human diet, " added Irina Fedorova, PhD, one of the paper's co-authors. EPA

is already known for its anti-inflammatory and cardiovascular effects, but DHA

makes up more than 90 percent of the omega-3s in the brain (which has no EPA),

retina and nervous system in general.

In the study, the researchers fed four different diets with no or varying types

and amounts of omega-3s to four groups of pregnant mice and then their

offspring. They measured how the offspring, once grown, responded to a classic

test of nervous-system function in which healthy animals are exposed to a sudden

loud noise. Normally, animals flinch. However, when they hear a softer tone in

advance, they flinch much less. It appears that normal nervous systems use that

gentle warning to prepare instinctively for future stimuli, an adaptive process

called sensorimotor gating.

Only the mice raised on DHA and EPA, but not their precursor of LNA, showed

normal, adaptive sensorimotor gating by responding in a significantly calmer way

to the loud noises that followed soft tones. The mice in all other groups, when

warned, were startled nearly as much by the loud sound. When DHA was deficient,

the nervous system most obviously did not downshift. That resulted in an

abnormal state that could leave animals perpetually startled and easily

overwhelmed by sensory stimuli.

The authors concluded that not enough DHA in the diet may reduce the ability to

handle sensory input. " It only takes a small decrement in brain DHA to produce

losses in brain function, " said Salem.

In humans, weak sensorimotor gating is a hallmark of many nervous-system

disorders such as schizophrenia or ADHD. Given mounting evidence of the role

omega-3s play in the nervous system, there is intense interest in their

therapeutic potential, perhaps as a supplement to medicines. For example, people

with schizophrenia have lower levels of essential fatty acids, possibly from a

genetic variation that results in poor metabolism of these nutrients.

More broadly, the typical American diet is much lower in all types of omega-3

than in omega-6 essential fatty acids, according to Salem. High intake of

omega-6, or linoleic acid, reduces the body's ability to incorporate omega-3s.

As a result, " we have the double whammy of low omega-3 intake and high omega-6

intake, " he said.

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Article: " Deficit in Prepulse Inhibition in Mice Caused by Dietary n-3 Fatty

Acid Deficiency " ; Irina Fedorova, PhD, Laboratory of Membrane Biochemistry and

Biophysics, National Institute on Alcohol Abuse and Alcoholism, National

Institutes of Health; Anita R. Alvheim, PhD candidate, Laboratory of Membrane

Biochemistry and Biophysics, National Institute on Alcohol Abuse and Alcoholism,

National Institutes of Health, and National Institute of Nutrition and Seafood

Research, Bergen, Norway; and Nahed Hussein, PhD and Norman Salem Jr., PhD,

Laboratory of Membrane Biochemistry and Biophysics, National Institute on

Alcohol Abuse and Alcoholism, National Institutes of Health; Behavioral

Neuroscience, Vol. 123, No. 6.