Lack of fish-borne brain nutrient linked to a problem characteristic of major brain and nervous system disorders
by Craig Weatherby
The omega-3 essential fatty acids found in fish and algae help animals avoid sensory overload, according to research published by the American Psychological Association.
The finding connects low omega-3 levels to the information-processing problems found in people with schizophrenia, bipolar disorder (manic-depression), obsessive-compulsive disorder, attention-deficit hyperactivity disorders (ADHD), Huntington's disease, and other afflictions of the brain and nervous system.
This new discovery relates to DHA, which one of the two key omega-3 fatty acids in fish fat: DHA and EPA.
It has long been known that DHA is critical to the structure and functions of cell membranes, and especially to brain cells.
“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., Ph.D., who led this study at the National Institute on Alcohol Abuse and Alcoholism: a division of the National Institutes of Health (NIH).
The body cannot make these essential nutrients from scratch. It gets DHA and EPA either by converting the plant-derived short-chain omega-3 fat called ALA – a very inefficient process – or from seafood, DHA-fortified eggs, or fish oil supplements.
While EPA is known for its anti-inflammatory effects, DHA makes up more than 90 percent of the omega-3s in the brain (which has no EPA), retina and nervous system in general.
Mouse study underlines importance of omega-3 DHA to brain health
The NIH 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 mice raised on plant-derived omega-3 ALA
—showed normal, adaptive sensorimotor gating by responding in a significantly calmer way to the loud noises that followed soft tones.
The mice in all the no-DHA groups were startled nearly as much by the loud sound even when it was preceded by the soft “warning” tone
Thus, when DHA was deficient, the animals’ nervous systems 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.
Implications for human health
In people, weak sensorimotor gating is a hallmark of many nervous-system disorders such as schizophrenia and ADHD.
Given mounting evidence of the role omega-3s play in the nervous system, there is intense interest in their therapeutic potential.
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 Dr. Salem.
High intake of the omega-6 fat called linoleic acid (LA) reduces the body's ability to incorporate omega-3s.
As a result, Dr. Salem noted, “we have the double whammy of low omega-3 intake and high omega-6 intake.”
- American Psychological Association (APA). Deficiencies may factor into mental illnesses. December 16, 2009. Accessed at http://www.eurekalert.org/pub_releases/2009-12/apa-nsl121609.php