Could a child’s dyslexia be the result of the mother’s diet?
The idea that our health may be determined in part by decisions made before we were born is an uncomfortable and controversial one. Yet vast amounts of data in the field of epigenetics is showing just that. And while “we are what we eat” is a cliche, it may be the case that diet is related to dyslexia.
We now know there is a strong genetic contribution to dyslexia – but genes do not provide the full story. Dyslexia’s genetic landscape is comparable to that of schizophrenia: studies have found particular chromosome sites that appear to be strongly implicated in certain families. In the overall population, a series of genes called alleles have their own (weak) individual effect.
Being born with the alleles associated with dyslexia does not necessarily mean you will develop it as a child: 50% of people who possess this particular genetic makeup have no difficulties reading. It merely indicates a certain vulnerability to the disorder. Instead, the difference between those who become dyslexic and those who don’t may rest on environmental factors before and after birth.
This is because alleles can be switched on or off by a biochemical process known as DNA methylation, which in turn depends on the balance of certain chemical agents in our bodies. Some believe this is controlled by diet in the early years of life and, most crucially, the diet of the mother before and during pregnancy. Gene-related defects that occur early on in development are often a consequence of which genes remain active and which do not.
The predominant theory of dyslexia has long been to class it as a “phonological processing problem”. While some dyslexic people experience visual issues, such as problems controlling eye movement, in other cases sustained difficulties in learning to read have been put down to problems with phonics – being able to split words into their constituent sounds and match them with the letters.
Scientists including professor John Stein at the University of Oxford have long been intrigued by the underlying neurological reasons behind these problems. Stein believes the answers lie with hearing. “In order to do phonics correctly, you’ve got to hear the order of sounds in the word very clearly,” he explains. “Many dyslexics hear the sounds, but they can’t get them in the right sequence because their auditory nerve cells are not working fast enough, and we think this is because of a lack of certain omega-3 fatty acids.”
One of the alleles believed to be associated with dyslexia is involved in metabolising these crucial omega-3 long-chain polyunsaturated fatty acids. One of these, docosahexaenoic acid (DHA), makes up 50% of the membranes of nerve cells in the auditory system, known as magnocells. DHA and eicosapentaenoic acid (EPA) are also involved in creating the myelination around nerve cells, which allows signals to pass more quickly.
When they work properly, auditory magnocells track rapid fluctuations in sound frequency and amplitude; the subtle cues that enable you to distinguish the sequence in which sounds occur. To do this, they require their membranes to be highly flexible and able to react quickly. However, Stein believes the development of these magnocells is impaired in many dyslexic people, and that this may be the result of a lack of DHA and EPA, both of which are found in fish oil.
Current recommendations suggest we should consume around 220mg of DHA a day. Our ancestors would easily have exceeded this, with fish forming one of the main components of their diets. However, since the advent of processed ready-meals, the amount we consume has fallen drastically. Last year, the British Nutrition Foundation found that around 80% of five- to 16-year-olds in the UK eat fewer than two portions of fish a week.
Both DHA and EPA are passed on to the unborn child in the womb, but if the mother has not consumed enough fish in her diet there will be a shortage, which may have a variety of consequences. With low quantities of DHA in the bloodstream, the allele responsible for metabolising it may be deactivated. DHA is also required for a variety of processes in the body, which will compensate by draining more from the already vulnerable magnocells.
The University of Oxford conducted a pilot study, which found that it was possible to improve the reading abilities of children by giving them supplements of DHA. A larger replication study is currently underway to try to confirm this finding.
“This particular building block for the brain is absolutely vital, especially for children who have a dyslexic parent or sibling, suggesting they may be genetically vulnerable,” Stein says. “For words that contain similar sounds, you need a very acute auditory processing system to pick up on those differences, so you need nerve membranes that react fast. If the child doesn’t get enough while they’re in the womb, the membranes won’t function properly.”
But not all dyslexia researchers are convinced. Some believe reading is on a higher cognitive plane, a process that cannot be affected by factors such as nutrition. “They don’t believe it can be dependent on something as low level as the quality of the nerve cell membranes,” Stein says. “There’s still a group of academic psychologists who believe the problem is not auditory processing but linguistics. They believe that dyslexic children have a problem with language per se. To me, there’s no such thing as language per se. Your language abilities piggyback on your auditory processing abilities.”
