However, I'm convinced on the efficacy of fish oil, at least for some young people, in helping with attention problems.
From a 2015 report of a study done of Dutch boys:
Those who regularly ate an omega-3-loaded margarine experienced an improvement in their ability to pay attention, compared with boys who did not, researchers report in the March 19 issue of Neuropsychopharmacology.
And from a 2005 report of a study done on children with developmental coordination disorder:
Pediatrics. 2005 May;115(5):1360-6.
The Oxford-Durham study: a randomized, controlled trial of dietary supplementation with fatty acids in children with developmental coordination disorder.
Developmental coordination disorder (DCD) affects approximately 5% of school-aged children. In addition to the core deficits in motor function, this condition is associated commonly with difficulties in learning, behavior, and psychosocial adjustment that persist into adulthood. Mounting evidence suggests that a relative lack of certain polyunsaturated fatty acids may contribute to related neurodevelopmental and psychiatric disorders such as dyslexia and attention-deficit/hyperactivity disorder. Given the current lack of effective, evidence-based treatment options for DCD, the use of fatty acid supplements merits investigation.METHODS:
A randomized, controlled trial of dietary supplementation with omega-3 and omega-6 fatty acids, compared with placebo, was conducted with 117 children with DCD (5-12 years of age). Treatment for 3 months in parallel groups was followed by a 1-way crossover from placebo to active treatment for an additional 3 months.RESULTS:
No effect of treatment on motor skills was apparent, but significant improvements for active treatment versus placebo were found in reading, spelling, and behavior over 3 months of treatment in parallel groups. After the crossover, similar changes were seen in the placebo-active group, whereas children continuing with active treatment maintained or improved their progress.CONCLUSIONS:
Fatty acid supplementation may offer a safe efficacious treatment option for educational and behavioral problems among children with DCD. Additional work is needed to investigate whether our inability to detect any improvement in motor skills reflects the measures used and to assess the durability of treatment effects on behavior and academic progress.
The improvements in reading and spelling were very striking, as discussed at the end of the study paper (I can't link to it because the text is not available without going behind a paywall):
In this kind of population, delays in literacy development usually increase over time, indicating the value of early intervention. Children in the placebo group fell even more behind with spelling during the 0- to 3-month parallel-group phase, although they did show average progress in reading. In contrast, children receiving active treatment made 3 times the expected normal gain in reading age and twice the normal gain in spelling age, bringing their average scores toward normative values. In the follow-up phase, they continued to make improvements above what would be expected for chronologic age.
My conclusion: Eat more cold-water, fatty fish or consider supplementation with omega-3 fatty acids--especially DHA and EPA, for ALA doesn't seem to help (see http://www.ncbi.nlm.nih.gov/pubmed/25339885)--if you think your children have problems with attention. There doesn't appear to be any harm from moderate supplementation, at least in the young. Brains need specific kinds of lipids to form and utilize efficient neural pathways, and it appears that fish oil somehow helps them get/make the needed substances.*
* Here are some tantalizing studies about fish oil and cognitive function, particularly in the young: http://www.ncbi.nlm.nih.gov/pubmed/12725043, http://www.ncbi.nlm.nih.gov/pubmed/18492851, http://www.ncbi.nlm.nih.gov/pubmed/15718358, http://www.ncbi.nlm.nih.gov/pubmed/21514362, http://www.ncbi.nlm.nih.gov/pubmed/26200950, http://www.ncbi.nlm.nih.gov/pubmed/25713056, http://www.ncbi.nlm.nih.gov/pubmed/25542508, and http://www.ncbi.nlm.nih.gov/pubmed/25498892.