A meta-analysis of blood fatty acids in people with learning disorders with particular interest in arachidonic acid

Small individual studies report that people with learning disorders have lower than normal blood concentrations of docosahexaenoic acid and arachidonic acid. The origin and consequence of the subnormal docosahexaenoic acid have been much speculated. However, relatively little attention has been paid to the significance of the low arachidonic acid concentration. Studies were identified through a literature search including subjects with various learning disorders or symptoms thereof and age-matched controls. A meta-analysis of pooled data from the red blood cell and plasma/serum showed that red blood cell arachidonic acid and docosahexanoic acid concentrations were significantly lower than normal [−3.93 and −18.92, respectively (weighted mean difference as a % of weighted mean control)]. Plasma/serum arachidonic acid and docosahexaenoic acid concentrations were also significantly lower than normal [−6.99 and −15.66, respectively (weighted mean difference as a % of weighted mean control)]. However, in absolute amounts the arachidonic acid was as severely depressed as docosahexanoic acid within red blood cells 0.57 mg/100 mg of fatty acid below normal verses 0.59 mg/100 mg for docosahexaenoic acid. Plasma/serum arachidonic acid was even lower; 0.71 mg/100 mg of fatty acid below normal verses 0.34 mg/100 mg for docosahexaenoic acid. The origin, consequences and relative importance of subnormal arachidonic acid to brain function bears further investigation.