DHA is found in high concentration in brain membrane phospholipids and is important for brain development and function through its influence on neurite outgrowth and neurotransmitter secretion. DHA plays vital role in transmitting impulses across nerve cells. Fusion of intracellular vesicles with the plasma membrane involving SNARE [soluble N-ethylmaleimide-sensitive fusion (NSF) protein attachment protein receptor] protein assembly, membrane fusion, and then disassembly are events common in membrane extension and neurotransmitter release. 

Studies with mice have shown that feeding an omega-3 fatty acid-deficient diet, known to reduce brain phospholipid DHA, alters SNARE protein and SNARE complex expression or protein nitrosylation in the hippocampus (seat of the memory) of rats. Hippocampus phospholipid DHA was lower and DPA (docosapentaenoic acid) was higher in the omega-3 fatty acid-deficient rats compared with the control group. These studies suggest that altered SNARE complex binding or disassembly could be important in explaining the diverse cellular events associated with altered tissue DHA.

Attention Deficit Hyperactivity Disorder (ADHD) and Fatty Acid Deficiency 

Growing body of evidence shows a possible link between attention deficit hyperactivity disorder (ADHD) and fatty acid deficiency. First evidence came in the early eighties when mild physical signs consistent with fatty acid deficiency were found among ADHD-afflicted patients. ADHD is associated with symptoms such as excessive thirst, frequent urination, rough, dull or dry skin, dandruff, soft or brittle nails, and follicular keratosis (a build-up of hard skin around the hair follicles that gives the skin a ‘bumpy’ appearance and feel). Animal studies have demonstrated fatty acid deficiency’s role in ADHD. Recently, several biochemical studies have also reported reduced concentrations of highly unsaturated fatty acids (HUFA) in the blood of ADHD children compared to controls. 

In one study comparing a sample of ADHD boys and controls revealed that regardless of clinical diagnosis, highly unsaturated fatty acids (HUFA) deficiency was correlated with a host of behavioral, learning and health problems. The interesting thing is that low levels of omega-6 fatty acids were related to some physical health measures (dry skin and hair, frequency of colds, and antibiotic use). Low omega-3 fatty acid status, on the other hand, was associated not only with physical signs of fatty acid deficiency (excessive thirst, frequent urination and dry skin) but also with behavioral problems (conduct disorder, hyperactivity-impulsivity, anxiety, temper tantrums and sleep problems) as well as learning difficulties in children.

Some studies have tried to uncover a possible mechanism how fatty acid deficiencies could lead to ADHD. Research has shown that omega-3 deficiency is associated with reduced levels of dopamine (and its binding to D2 receptors) in frontal cortex, a brain region. It is well known that dopamine is the main neurotransmitter boosted by the stimulant medications used to treat ADHD. Detailed studies indicated that the reduced availability of dopamine in these regions of brain due to omega-3 deficiency may be insufficient to maintain the high release needed during ‘stimulated cognitive processes’ such as sustained attention to a demanding task.