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DYSLEXIA, DYSPRAXIA and ADHD - CAN NUTRITION HELP?
Alexandra J. Richardson
Senior Research Fellow in Neuroscience, Imperial College School of Medicine, MRI Unit, Hammersmith Hospital, London; and University Lab. of Physiology, Oxford.
INTRODUCTION
There is a wide spectrum of conditions in which deficiencies of highly unsaturated fatty acids (HUFA) appear to play a role (Glen et al, 1999). This includes atopic (allergic) conditions such as eczema and asthma as well as psychiatric disorders such as schizophrenia and depression. The focus here is on the role of HUFA in three common learning and behavioural disorders - dyslexia, dyspraxia and attention- deficit / hyperactivity disorder (ADHD), although similar issues may also be relevant to the autistic spectrum (Richardson and Ross, 2000).
Dyslexia alone affects at least 5% of the general population in a severe form, as does ADHD, although estimates rise when milder forms are included. Dyspraxia remains less well-known, but prevalence appears to be similar. There is considerable overlap between dyslexia, dyspraxia and ADHD and each can occur with differing degrees of severity. Current evidence suggests that up to 20% of the population may be affected to at least some degree by one or more of these conditions. The associated difficulties usually persist into adulthood, causing serious problems not only for those affected, but also for society as a whole.
DYSLEXIA, DYSPRAXIA and ADHD - CLINICAL FEATURES
The clinical overlap between these conditions is substantial: each can appear in isolation, but very often the same individual will show features of two, or even all three, of these disorders. Unfortunately, there is usually no such overlap in diagnosis and management. Official diagnosis of ADHD lies in the realm of psychiatry, with stimulant medication as the most likely treatment. Dyslexia is usually seen as an educational or psychological problem, and management is usually by these methods. Dyspraxia is the least recognised of the three, and if it is diagnosed at all, referral will often be to a physiotherapist or occupational therapist.
Dyslexia
The defining feature here is specific problems in learning to read and write in relation to general ability or IQ, but problems with arithmetic and reading musical notation are also common. Poor working memory - especially for sequenced, auditory-linguistic material - is a central characteristic, and difficulties with phonology (the sounds in words) are often regarded as a core feature, although these are typically found in any poor readers. Associated features include problems in distinguishing left and right, poor direction sense, difficulties with time and tense, and subtle problems with both visual and auditory perception. The overlap with ADHD is around 30-50%, and with dyspraxia it may be even higher.
There is a clear biological basis to dyslexia. Genetic studies suggest heritability of around 50%, prevalence across cultures is similar (and independent of socio-economic status and IQ), and more males than females are affected. Differences in brain structure in dyslexia include an unusual symmetry of language areas and microscopic differences in the arrangement and connection of neurons. The visual and auditory problems point to a mild disorder of ‘magnocellular’ systems, specialised for very rapid information processing.
Dyspraxia
Core problems involve difficulties in planning and carrying out complex, sequenced actions. In motor co-ordination, this shows in clumsiness, difficulties with catching a ball or balancing, tying shoelaces or doing up buttons. However, dyspraxic children often have extremely poor handwriting, if not the other features of dyslexia, and difficulties with organisation, attention and concentration, as in ADHD, are very common. Dyspraxia is also associated with poor memory for symbolic material, both visual and auditory, and often with impulsivity and temper tantrums. These children can be hypersensitive to touch, smells and sounds, and they often prefer repetitive, familiar activities because they can find novel situations very stressful.
ADHD
The central problems here involve Inattention , i.e. persistent difficulties with sustained attention and concentration, and/or Hyperactivity - Impulsivity. Hyperactive-Impulsive children show excessive motor activity and restlessness, an inability to regulate behaviour according to the situation, and difficulty delaying gratification. Attentional problems are not always so obvious unless they occur together with hyperactivity, but these alone can create equally serious problems of under-achievement. A large proportion of ADHD children (around 50%) also show clinical features of dyslexia and/or dyspraxia, as noted above, although these associations are stronger for the Inattentive form of ADHD than for Hyperactivity-Impulsivity.
ESSENTIAL LIPIDS AND BRAIN FUNCTION
To understand how fatty acid abnormalities could play a role in these conditions requires an appreciation of their essential role in brain structure and function. Two fatty acids (AA and DHA) play a major structural role in the brain and eye, making up 20% of the dry weight of the brain and more than 30% of the retina. Two others (EPA and DGLA) play a more minor structural role but are also crucial for normal brain function. EPA, DGLA and AA are all substrates for different series of prostaglandins and other molecules that play a critical role in the moment-by-moment regulation of a wide range of brain and body functions.
The truly essential fatty acids (EFA) which cannot be synthesised by the body and must therefore be provided in the diet are linoleic acid (omega-6 series) and alpha-linolenic acid (omega-3 series). The longer-chain highly unsaturated fatty acids (HUFA) that the brain needs can usually be synthesised from these EFA precursors via processes of desaturation (insertion of a double-bond) and elongation (adding two carbon atoms to the fatty acid chain).
Pathways for the synthesis of omega-6 and omega-3 fatty acids
Omega-6 Fatty Acids Omega-3 Fatty Acids
Enzymes involved Linoleic (LA) 18:2 Alpha-linolenic (ALA) 18: (^9) Delta 6- desaturase 9 Gamma-linolenic (GLA) 18:3 Octadecatetraenoic 18: (^9) Elongase 9 Dihomogamma-linolenic (DGLA) 20:3 Eicosatetraenoic 20: (^9) Delta 5-desaturase 9 Arachidonic (AA) 20:4 Eicosapentaenoic (EPA) 20: (^9) Elongase 9 Adrenic 22:4 Docosapentaenoic (DPA) 22: (^9) Elongase, Delta 6- 9 Docosapentaenoic (DPA) 22:5 desaturase, Beta-oxidation Docosahexaenoic (DHA) 22:
that supplementation with pure DHA was completely ineffective in ADHD another large controlled trial (Voigt et al, 1999). This is consistent with other evidence that EPA, rather than DHA is probably the important omega-3 fatty acid for management of the attentional, cognitive and other problems associated with ADHD.
Evidence for fatty acid deficiency in Dyspraxia
In children with dyspraxia, so far only open trials of fatty acid supplementation have been carried out (Stordy, 1997). 15 children whose performance on standardised measures of motor skills initially placed them in the bottom 1% of the population were treated with a supplement containing DHA, EPA, AA and DGLA. They were then retested after 12 weeks. After supplementation, improvements were found on objective measures of manual dexterity, ball skills, and static and dynamic balance, as well as on parental ratings of the children’s dyspraxic symptoms. In addition, ADHD symptoms in these children (Conners Parent Rating Scale) were also reduced following the fatty acid treatment.
Evidence for fatty acid deficiency in Dyslexia
- Visual function in dyslexia improved by fatty acid treatment Stordy (1995) proposed that fatty acid treatment may help in the management of dyslexia. She had first observed an apparent association between breastfeeding (and its duration) in relation to the severity of dyslexia, as well as poor night vision in dyslexic individuals. She therefore tested dyslexic adults and found they showed impaired dark adaptation, but this visual problem normalised after just 4 weeks of supplementation with the omega-3 fatty acids EPA and DHA. The role of omega-3 fatty acids in visual function is well recognised, and the evidence for visual problems in dyslexia is now substantial. Stordy’s 1995 findings not only suggested a possible biochemical basis for these which might also help to explain other features of dyslexia, but also suggested new treatment possibilities.
- Abnormal brain lipid metabolism in dyslexia revealed by brain imaging To investigate the proposal that membrane lipid metabolism in dyslexia may be abnormal, a study was carried out at the MRI Unit at Hammersmith Hospital (Richardson et al., 1997). MR imaging is a safe and non-invasive technique involving the use of radiowaves within a very strong magnetic field. It can be used to obtain either structural images (the well-known MRI) or information on the chemical composition of tissues (magnetic resonance spectroscopy, or MRS). To study membrane lipid metabolism in the living brain, 31-phosphorus MRS is the best available technique. From 31- phosphorus MRS spectra, seven different phosphorus metabolites can be clearly identified, and their concentrations measured. Two of these provide information on membrane lipid turnover: phosphomonoesters (PMEs) include the precursors of membrane phospholipids, while phosphodiesters (PDEs) index their breakdown products. Results showed a clear excess of PMEs in dyslexic adults compared with controls, suggesting a problem in the synthesis of membrane phospholipids in dyslexia, while PDE levels were normal. These results are also compatible with deficiency in certain HUFA in dyslexia. (PMEs have to combine with diacylglycerols - molecules with two fatty acids - to form membrane phospholipids. If these molecules do not contain the ‘right’ fatty acids, then this process could be impaired, resulting in an accumulation of the PME precursors.)
- Blood biochemical abnormalities in dyslexia In a single case report, Baker (1985) found fatty acid deficiencies on biochemical testing of a dyslexic boy who also showed overt clinical signs such as rough, dry skin and hair. More recently, MacDonell et al (2000) found that dyslexic adults showed increased levels of a PLA2 enzyme that removes HUFA from membranes.
- Clinical signs of fatty acid deficiency in dyslexia In a large sample of dyslexic and non-dyslexic adults, clinical signs of fatty acid deficiency were significantly higher in the dyslexic group (Taylor et al., 2000). These signs were assessed using the same scale as was used in recent studies of ADHD (Stevens et al., 1995), where fatty acid
deficiency scores were also related to blood biochemical measures of fatty acid deficiency. Within dyslexic children, those with more clinical signs of fatty acid deficiency had more severe difficulties in reading, spelling and working memory (Richardson et al, 2000). However, there was no evidence that fatty acid deficiency was confined to any particular subgroup as defined by psychometric tests.
- Double-blind treatment trials in dyslexia - preliminary results In view of the mounting evidence for fatty acid abnormalities in dyslexia, several double-blind clinical trials were set up to assess whether treatment with fatty acids can be of benefit in this condition (Richardson et al, 1999). These studies are now approaching completion, and some preliminary results are already available.
Trial 1 : In a school-based study, 41 dyslexic children with ADHD features took either a fatty acid supplement (mainly fish oil with some evening primrose, supplying EPA, DHA, GLA and some AA) or a placebo (containing olive oil) for three months. They were assessed before and after treatment on standard parent ratings of ADHD symptoms (Richardson et al, 2000). ÿ Compared with the placebo-treated group, those dyslexic children who had received the fatty acid supplement showed significant reductions in a range of ADHD symptoms, particularly cognitive problems (inattention, learning and memory problems) and anxiety. ÿ In a second stage of the study, those children who had received the placebo treatment were then switched to the fatty acid supplement under single-blind conditions and followed for a further 3 months. In these children, significant improvements were observed for a wide range of ADHD measures, in striking contrast to the lack of improvement they had shown on placebo treatment. Numbers in this study were small, so these results need to be confirmed in larger double-blind trials still underway. However, they provide promising evidence that dietary supplementation with HUFA can be of some benefit in the management of ADHD-related symptoms in dyslexia.
Trial 2: In a larger clinic-based study, 102 dyslexic children took either the same fatty acid supplement or placebo for six months under double-blind conditions. Supplementation was associated with significant improvements in reading, especially for children with fatty acid deficiency signs or visual symptoms at baseline.
FREQUENTLY ASKED QUESTIONS
1. Is fatty acid deficiency more likely in ADHD, dyslexia,or dyspraxia?
In my view, these kinds of diagnostic labels should usually be treated with more than a degree of caution. There is huge variability in both access to formal assessments and the diagnostic methods used. All of these conditions exist in graded form, with core features often blending imperceptibly into the general population range. More importantly, perhaps, the overlap between these conditions in practice is so great that so-called ‘pure cases’ are the exception rather than the rule.
Research suggests that a significant proportion of people with any or all of these conditions (and some others with no such official label) could be helped by simple dietary supplementation with highly unsaturated fatty acids. However, it must be emphasised that: (i) this approach can’t be expected to benefit every individual with dyslexia, dyspraxia or ADHD
- simply because the causes of these kinds of problems can be so varied, and (ii) although good nutrition is the foundation for optimal brain function, many other factors obviously need to be considered in the management of these conditions. Our treatment trials have involved children and adults identified primarily for either dyslexia or ADHD. However, we have taken care to assess features of all three conditions as far as possible. (For the record, more than half of our dyslexic and ADHD children met clinical criteria for dyspraxia, and we found the usual high overlap between dyslexia and ADHD in both children and adults). In our adult study, we also included a non-dyslexic group, and we assessed them using the same measures, as there is already some evidence of benefits from HUFA supplementation in the general population.
any ‘failure’ very much to heart. Omega-3 supplementation has been shown to reduce susceptibility to stress-aggression in ordinary students under pressure. Results from our studies also suggest a good response to fatty acid supplements by those with a very low tolerance for frustration, i.e. those who are prone to either emotional outbursts or undue anxiety-tension when things don’t go as planned. It is noteworthy that omega-3 deficiencies are implicated in mood disorders, both depressive and bipolar (manic-depressive). Children with these traits often meet criteria for ADHD, and may perhaps represent a subgroup who would respond well to fatty acid supplementation, although this too requires further study.
- Sleep problems Certain HUFA are required for the manufacture of prostaglandins, and among many other functions, these molecules play an important part in determining sleep onset and offset. Fatty acid imbalances could therefore be a factor in some kinds of sleeping problems, and research evidence supports this, although few if any clinical studies have yet been carried out. Subjective reports from participants in our treatment trials strongly suggest that fatty acid supplementation may help to improve sleep for some people, particularly if difficulties in getting to sleep at night (and corresponding difficulties waking up in the morning) were previously characteristic. Perhaps unsurprisingly, those who respond to supplementation in this way usually report other benefits. These may all be a consequence of the improvements in sleep, or they may represent other effects of fatty acid supplementation in these individuals. In either case, this issue clearly deserves further study. 3. What kind of supplements will work best?
First, it should be re-emphasised that fatty acid supplements will not ‘work’ for everyone. Some people already get all the HUFA they need via their diet and/or their own metabolism. Individual differences in constitution, diet and lifestyle are all important, so there can be no universal answers. However, the following points may help to provide some guidance for those interested in trying supplementation.
Omega-3 fatty acids play a crucial role in eye and brain function, yet these are the ones most likely to be lacking from modern diets. In theory, we can build complex fatty acids for ourselves from simpler ones. However, even the simple omega-3 fatty acids are lacking in many people’s diets (particularly if they mainly eat processed foods), and in some people, the conversion process of simple fatty acids into the longer-chain, highly unsaturated ones may be inefficient. The only way to get the complex omega- 3 fatty acids (EPA and DHA) directly from the diet is by consuming large amounts of oily fish and seafood on a regular basis. This is often impractical, so fish or marine oil supplements are sometimes the only realistic option.
Omega-6 fatty acids are also important, with evening primrose oil being the best-known supplement source. Evening primrose alone often helps with the dry skin problems and allergies common in people with ADHD, dyslexia and dyspraxia (and often found in their relatives). However, early studies using evening primrose oil alone showed only marginal benefits, if any, for the central problems with learning and behaviour. For brain function, the omega-3 fatty acids seem to be more important, but these are less common in our food supply than omega-6.
In most cases it therefore probably makes sense to supplement mainly with fish oil (providing the omega-3 HUFA) but many people may benefit from a little evening primrose oil in addition.
Omega 3: EPA versus DHA? Fish oil contains two major omega-3 fatty acids: EPA and DHA. Both are necessary, but until recently, it wasn’t at all clear which of these was more important in producing the benefits reported for ADHD and related conditions. In early life, plenty of DHA is needed for the growing brain – and because this fatty acid is so important for actual brain structure, it was thought that this must be reason for the apparent benefits from fish oil. However, the latest research has now shown that it is EPA, not DHA, which is more effective in reducing the problems with attention, perception and memory that are associated with ADHD, dyslexia and dyspraxia. This is probably because EPA plays a more important role in the minute-by-minute functioning of the brain, and also helps to make other substances (such as prostaglandins) that are crucial for proper signalling between
cells. In addition, new evidence suggests that EPA may actually help in another way – by helping to protect all of the long-chain highly unsaturated fatty acids against rapid breakdown and loss. For these reasons, supplements with a high ratio of EPA to DHA are likely to be most effective.
A note of caution should also be sounded about cod-liver oil – or any fish liver oil – for these purposes. These do provide an excellent source of omega-3 fatty acids for general use, but they also contain significant levels of Vitamin A, which can be harmful in excess. One or two capsules a day should present no problems, but if high doses of fish oil are to be taken on a regular basis, the fish liver oils are probably best avoided.
A final point concerns the quality of oils used. The popularity of both evening primrose and fish oils has led to a huge number of different supplements becoming available. Unfortunately, not all of these are of good quality, and in some cases, they may not only be ineffective, but could even contain harmful residues (either from environmental pollution or from the methods of extraction and processing used). Any reputable supplier should be able to provide information on both the source of their oils and their manufacturing methods, but at the very least, it should not be assumed that the cheapest supplements are the best value. Another point is that Vitamin E is usually included in HUFA supplements as an antioxidant to protect these fatty acids from breakdown. If it is not, additional Vitamin E supplementation may be required.
4. Are there any negative side-effects from fatty acid supplements? What dosage is appropriate?
Highly unsaturated fatty acids are safe even in extremely large doses, and their regular consumption carries a wide range of positive health benefits. They are foodstuffs, not drugs – and moreover, they used to form an important part of our natural diet for centuries, but have been disappearing from our food in recent decades. The only known side-effects of fatty acid supplements involve mild digestive upset, although this affects very few people. Small divided doses taken with plenty of food can often eliminate such problems (and it is worth noting that choosing a high-quality oil should also help to reduce any fishy aftertastes!).
The appropriate dosage will vary between individuals (and in the same individual over time). It is also very important to recognise that it can sometimes take up to three months for the maximum benefits from supplementation to become apparent, owing to the slow turnover of these fatty acids in the brain. Unlike medications, they do not work rapidly to change mental functioning, and although we have found that some individuals report clear benefits as rapidly as two weeks after starting supplementation, in other cases the changes are much more gradual.
A higher dose is therefore usually recommended for this ‘trial period’. An initial dosage of fish oil supplying around 500mg daily of EPA is probably most appropriate for dyslexia and related conditions, and if evening primrose is also included, around 50mg per day of GLA (which converts easily to DGLA and AA) is likely to be sufficient. After three months, reducing the dose to half or one-third of these levels may be appropriate, but requirements vary – both between individuals and according to circumstances - so dosages are best determined from experience and careful personal monitoring. We have found that some people may need high levels on a long-term basis to prevent symptoms from re-appearing.
Informing the GP is strongly recommended before embarking on any kind of dietary supplementation, and this is obviously essential if someone is already taking any medications or being treated for any other condition.
As emphasised throughout, not everyone can expect noticeable benefits from taking fatty acid supplements. If no improvements are apparent within three months of starting this kind of dietary treatment, then it is reasonable to conclude that fatty acid deficiency is not a major factor for that individual. Other approaches to managing dyslexia, dyspraxia and ADHD should always be considered in any case.
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