Can Nutrition Make a Difference?
What do oily fish have to do with dyslexia?
It sounds like an odd question until we remember that the brain is a biological organ. Neurons do not communicate in isolation from the materials from which they are built. Their cell membranes contain substantial quantities of specialised fatty acids, including the long-chain omega-3 fatty acid DHA.
This led researchers including Dr Alex Richardson and Professor John Stein, who I worked with at Oxford University to ask whether differences in fatty-acid status might influence aspects of brain function relevant to dyslexia.
There is also a lighter connection: John Stein is the brother of chef Rick Stein. One became known for neuroscience and the other for fish. Behind the coincidence lies a serious scientific question: can nutrition influence the development and functioning of neural systems involved in learning and reading?
Why omega-3?
Long-chain polyunsaturated fatty acids are important components of neuronal membranes. DHA is particularly abundant in the brain and retina.
Richardson and Ross (2000) proposed that abnormalities of fatty-acid and membrane phospholipid metabolism might contribute to neurodevelopmental conditions including dyslexia, ADHD and developmental coordination disorder. Taylor and Richardson (2000) explored possible relationships among fatty acids, visual function and magnocellular processes.
A plausible biological mechanism, however, is only the beginning of an argument. It does not demonstrate that people with dyslexia are omega-3 deficient, nor that taking fish oil improves dyslexia.
Fatty-acid status and reading
Richardson, Calvin et al. (2000) studied 97 children with dyslexia. Children showing more physical signs previously associated with fatty-acid deficiency had poorer reading and lower general ability. Among boys, these signs were also associated with poorer spelling and auditory working memory. The same significant pattern was not demonstrated in the smaller group of girls.
The findings supported further investigation but were correlational. They could not establish that fatty-acid deficiency caused reading difficulty.
Cyhlarova, Bell et al. (2007) later examined red-blood-cell membrane fatty acids in dyslexic and non-dyslexic adults and related them to reading and spelling. Associations were reported between aspects of fatty-acid status and literacy, but the dyslexic and comparison groups were not simply distinguished by a general omega-3 deficiency.
What happens when omega-3 is given?
Richardson and Montgomery's (2005) Oxford-Durham trial involved children with developmental coordination disorder. Fatty-acid supplementation did not improve the study's primary motor outcome, but the active-treatment group showed greater improvements in reading, spelling and behaviour than the placebo group.
It is important not to retell this as a dyslexia trial: the participants were selected for developmental coordination disorder.
The DOLAB study later tested 600 mg DHA daily in children who were underperforming in reading. There was no significant reading benefit across the full sample, although a subgroup with poorer initial reading appeared to improve more with DHA. A subsequent DOLAB II trial specifically attempted to replicate the effect in children below the 20th reading centile and did not find a consistent DHA advantage for reading, working memory or behaviour.
Negative replication is as important scientifically as an initially promising result.
What does the overall evidence say?
Systematic review evidence remains cautious. The available trials do not justify presenting omega-3 supplementation as a treatment for dyslexia or specific learning disorder.
That is different from saying that omega-3 is irrelevant to brain function. DHA is biologically important; fatty acids are essential components of neuronal and retinal membranes; and nutrition can influence health and development. The unresolved question is whether supplementation produces a clinically meaningful improvement in reading for children with dyslexia who are not otherwise deficient.
My interest in this literature is also personal to my research history: I worked with Alex Richardson within the Oxford/FAB research environment where nutrition, sensory processing and neurodevelopment were being investigated together.
A multi-level account of dyslexia
What remains compelling about this research is its attempt to connect different levels of explanation.
At one level there is behaviour: a child struggles to read. Below that are cognitive processes such as phonological processing, orthographic learning, attention and memory. Below those are sensory and neural processes, including auditory timing, visual motion processing and neuronal signalling. Below those again are biological processes including genes, neural development, cell membranes and nutrition.
Research does not allow us to draw a simple arrow from fish oil to improved reading. At INPSYGHT, nutrition would never replace comprehensive dyslexia assessment or evidence-based reading instruction. Equally, sleep, diet, physical health, attention and emotional wellbeing can form part of understanding the whole child.
Dyslexia is not caused by failing to eat enough fish. Omega-3 supplementation is not an established treatment for dyslexia. But research into how nutrition influences the developing brain remains scientifically important, and the connections among dyslexia, Oxford neuroscience, John Stein, Alex Richardson and Food and Behaviour Research form an important part of that history.
References
Richardson, A.J. & Ross, M.A. (2000). Fatty acid metabolism in neurodevelopmental disorder: a new perspective on associations between attention-deficit/hyperactivity disorder, dyslexia, dyspraxia and the autistic spectrum. Prostaglandins, Leukotrienes and Essential Fatty Acids, 63, 1-9.
Richardson, A.J., Calvin, C.M. et al. (2000). Fatty acid deficiency signs predict the severity of reading and related difficulties in dyslexic children. Prostaglandins, Leukotrienes and Essential Fatty Acids, 63, 69-74.
Taylor, K.E. & Richardson, A.J. (2000). Visual function, fatty acids and dyslexia. Prostaglandins, Leukotrienes and Essential Fatty Acids, 63, 89-93.
Richardson, A.J. & Puri, B.K. (2002). A randomized double-blind, placebo-controlled study of the effects of supplementation with highly unsaturated fatty acids on ADHD-related symptoms in children with specific learning difficulties. Progress in Neuro-Psychopharmacology & Biological Psychiatry, 26, 233-239.
Richardson, A.J. & Montgomery, P. (2005). The Oxford-Durham study: a randomized, controlled trial of dietary supplementation with fatty acids in children with developmental coordination disorder. Pediatrics, 115, 1360-1366.
Cyhlarova, E., Bell, J.G. et al. (2007). Membrane fatty acids, reading and spelling in dyslexic and non-dyslexic adults. European Neuropsychopharmacology.
Tan, M.L. et al. (2016). Polyunsaturated fatty acids (PUFAs) for children with specific learning disorders. Cochrane Database of Systematic Reviews, CD009398.
Montgomery, P. et al. / DOLAB research programme. DHA supplementation and reading outcomes in school-age children, including subsequent replication work.