Animal study: high levels of omega-3 fatty acids may protect against sensory overload

A diet high in omega-3 fatty acids may help people avoid sensory overload, a new study suggests. An inability to process incoming sensory information efficiently is seen in a wide range of nervous system conditions including attention deficit hyperactivity disorder (ADHD), bipolar disorder, obsessive-compulsive disorder, and schizophrenia.

Irina Fedorova and colleagues fed different diets to four groups of pregnant mice and their offspring. One diet was high in the omega-3 fatty acids docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), and a-linolenic acid (LNA). The other diets contained no EPA or DHA but were high, low, or deficient in LNA. LNA is a precursor of DHA and EPA; however, the researchers note that the body converts less than 1% of LNA into DHA and that DHA makes up more than 90% of the omega-3 fatty acids in the brain.

The researchers tested the offspring by exposing them to a sudden, loud noise. Animals normally flinch when they hear the sound, but they react less violently if they are exposed to a softer tone beforehand. This adaptive blunting of the nervous system’s response to future stimuli after a first exposure is called “sensorimotor gating.”

Fedorova and colleagues say the mice who received DHA and EPA exhibited normal sensorimotor gating, showing a reduced startle response to the loud tone when a softer tone preceded it. The mice in the other three groups, however, were unable to “downshift” their response to the second tone. Mice in the deficient-LNA and low-LNA diets exhibited a substantial deficit in sensorimotor gating, while those receiving the high-LNA diet exhibited a smaller but still significant deficit.

This abnormal response, the researchers say, may cause omega-3-deficient animals to be easily overwhelmed by sensory stimuli. “It only takes a small decrement in brain DHA to produce losses in brain function,” study coauthor Norman Salem says.

Omega-3 fatty acids are essential for brain and eye development. The body needs to obtain these nutrients through food or supplements because it cannot synthesize them from scratch. Salem says, “It is an uphill battle now to reverse the message that ‘fats are bad,’ and to increase omega-3 fats in our diet.”

Salem notes that most humans eat diets very low in omega-3 fatty acids, which are found in foods including fish, nuts, flaxseed, and green, leafy vegetables. (See related article on page 6.) In addition, people typically eat diets high in omega-6 fatty acids, which reduce the body’s ability to use omega-3. As a result, he says, “we have the double whammy of low omega-3 intake and high omega-6 intake.”