Attention deficit hyperactivity disorder (ADHD) is defined as the combination of inattentive, hyperactive and impulsive behavior which are severe, developmentally inappropriate, and impair function at home and in school. Common features include mood swings, anxiety, impulsivity, hostility, poor concentration and sleeping disorders, along with physical complaints such as headaches, migraines, and stomach upsets. ADHD individuals are also more likely to have been of low birth weight and to have allergies or auto-immune problems. Proportionally more males than females are affected, with inattention tending to be a more female trait and hyperactivity more common in males.
ADHD does persist into adulthood, although symptoms tend to diminish with time, but the main focus relates to the problems of children with ADHD. Growing children are especially vulnerable to nutritional and environmental factors that influence brain development and function, which can have either a negative or positive impact. The symptoms of this difficult condition can also significantly compromise their education, making them challenging to teach and consequently having a deleterious effect on their life-potential. The daily challenges of living with ADHD place a huge strain on families and reduces overall quality of life for all involved.
Back in 1981, Colquhoun and Bunday undertook a comprehensive survey of children with ADHD and discovered that many showed physical signs of essential fatty acid (EFA) deficiency, including excessive thirst, polyuria, dry hair and skin. These authors were the first to propose that fatty acid deficiency may be a factor in ADHD, and their ground-breaking work prompted more research studies and clinical trials designed to increase understanding of those nutritional factors involved in ADHD.
It has now been proposed that many developmental and psychiatric conditions, including ADHD along with dyslexia, dyspraxia, autism, depression, and schizophrenia, may involve deficiencies of certain long-chained fats, especially eicosapentaenoic acid ( EPA) and docosahexaenoic acid (DHA). Both iron deficiency and zinc deficiency have also been associated with the development of ADHD.
Fats have a fundamental structural and functional role in the brain and central nervous system (CNS) and are a key factor in the development ADHD. The two fats that are thought to be especially important are EPA and DHA, not only because of their role in the brain and body but because of the relative lack of them in many people’s diets. EPA is the precursor of a complex group of substances, called eicosanoids, which perform numerous regulatory functions in the brain and body. DHA is a major ‘building block’ of brain and neuronal membranes and as such has a profound influence on cell signalling. Both EPA and DHA are omega-3 fats and can be made from the omega-3 essential fatty acid, alpha linolenic acid (ALA). However, this conversion process can be problematic as genetic and environmental factors, including diet, can cause great variation in an individual’s constitutional ability to convert ALA into EPA and DHA. Dietary factors known to adversely affect this conversion include low intakes of ALA, high intakes of omega-6 fats, saturated fat, hydrogenated fat and alcohol, in addition to vitamin and mineral deficiencies, testosterone and stress hormones. Unfortunately, many dietary surveys have revealed that a typical modern-day diet is rich in omega-6 fats, saturated fats and hydrogenated fats and often low in omega-3 fats and micronutrients. ADHD children are often found to be deficient in iron and zinc and the fact that more boys than girls tend to be affected may be partly explained by the negative effect of testosterone on this conversion process.
In order to avoid a functional deficiency of these important fats, the diet should have a smaller ratio of the omega-6 essential fat, linoleic acid (LA) to omega-3 essential fat (ALA), at an ideal ratio of no more than 5:1, as well as adequate amounts of pre-formed EPA and DHA. The richest dietary sources of LA are certain vegetable and seed oils, including sunflower, safflower, soya, palm, peanut and sesame, all of which should be eaten in good amounts along with oils that are rich in ALA such as rapeseed (canola), flaxseed (linseed) and walnut oil. Olive oil is also recommended, despite having quite a low ALA content, as it is rich in beneficial monounsaturated fats. Looking at types of spreading fat available, many margarines have been specifically formulated to be rich in ALA, although some brands still contain harmful hydrogenated fats, but it is worth remembering that butter actually has a low LA content and when mixed with equal quantities of rapeseed or olive oil, the saturated fat content is much reduced. Other sources of ALA include green, leafy vegetables such as rocket, watercress and spinach as well as fresh green herbs, such as basil, coriander, mint and parsley. Consequently, the food products of animals allowed to graze on open pasture will also be rich in ALA and so organic, free-range and outdoor-reared meat, milk and eggs are the best choice.
When it comes to sources of EPA and DHA, fish and seafood are the best sources with oily fish , such as salmon, trout, mackerel, sardines, herring and anchovies, being especially rich. Fresh tuna is classed as an oily fish but the canning process causes a significant loss of fatty acids so tinned tuna has an EPA and DHA content comparable to white fish, such as cod, haddock and plaice. Certain varieties of fish are more likely to contain large amounts of pollutants such as mercury and lead which are known to be neurotoxic and so it is prudent for people with ADHD, and all children under 16 years of age, to avoid eating shark, marlin and swordfish. DHA can also be found in liver and egg yolks and so these foods should be incorpo rated into the diet regularly, unless you are taking a nutritional supplement that contains vitamin A in which case you should not eat liver or foods containing liver such as pâté.
If intakes of long-chained polyunsaturated fats (PUFAs), such as EPA and DHA, increase then so does the risk of lipid peroxidation by the action of harmful free radicals, smoking, and pollutants, etc.; substances produced in the body by normal processes such as breathing and metabolism. PUFAs are highly susceptible to attack from these reactive substances and need the protection of antioxidants to avoid getting damaged and thus affecting the structure of the lipid membranes of the brain and CNS. When free radical production is insufficiently countered by antioxidants the resultant damage to the brain and body is termed ’oxidative injury’.
Dietary antioxidants include nutrients such as vitamin E and selenium as well as biologically active substances such as flavonols, anthocyanins and carotenoids, found in highly colored fruits and vegetables, nuts, tea and red wine. Vitamin E is naturally found in PUFA-rich foods like oils and nuts whilst selenium is found in fish, seafood, liver, egg, brazil nuts, mushrooms and lentils. Eating the recommended daily minimum of 5 portions of fruit and / or vegetables should provide adequate amounts of complementary dietary antioxidants, especially if a wide range of colors and varieties are chosen.
Iron deficiency has been associated with ADHD in children and tends to be worse even when compared with iron-deficient non-ADHD controls. Lower serum ferritin levels correlate with more severe ADHD symptoms and greater cognitive deficits.
Dietary sources of iron include red meat, fortified breakfast cereals, pulses and dried apricots and these foods should feature regularly in the ADHD diet. Additional supplementary iron may be required in cases of proven iron deficiency.
Zinc has a range of important functions in the body, including the metabolism of neurotransmitters and fatty acids, with zinc deficiency possibly having an effect on the development of ADHD. Children with ADHD who have been treated with supplementary zinc have exhibited reduced hyperactive, impulsive and impaired-socialisation symptoms.
Foods known to be rich in zinc include seafood, liver, pine nuts, cashew nuts and wholegrain cereals and so should be eaten regularly to help avoid deficiency.
Synthetic Food Additives
Certain synthetic food colorings, flavorings and preservatives, have been linked to increase hyperactivity in some ADHD and non-ADHD children. Many of these additives are unnecessary and are frequently used to sell poor-quality foods, that are often marketed specifically at children.
The following additives have been implicated in adverse reactions:
* benzoic acid
* sodium benzoate
* sodium metabisulphite
* sulphur dioxide
The ADHD diet works by providing the right type and amount of fats needed for the brain and CNS as well as providing sufficient amounts of iron and zinc to avoid nutritional deficiencies that are known to be associated with worsening ADHD symptoms. Nutritional supplements should be taken upon the advice of a Doctor or Dietitian and taken in addition to a healthy, balanced diet. Dietary provision of antioxidants are needed to protect the long-chained fats from breakdown which would affect brain structure and compromise signalling within the brain and CNS. Finally, the ADHD diet excludes those synthetic food additives that have been identified as having the potential to adversely affect the behavior of ADHD, and non-ADHD children alike.
The key benefit of the ADHD diet is that it provides the correct types of foods needed to support the nutritional requirements of both the brain and body. It provides the nutrients needed to sustain good growth and development in children, as well as general health promotion for all, whilst excluding potential antagonistic additives. The diet supports other treatment strategies, including stimulant medication, and so helps to improve the quality of life and educational possibilities of those individuals affected.
Detailed, personalized advice should always be sought from a suitably qualified dietitian, especially when dealing with children. Any nutritional supplements should always be taken according to the manufacturers instructions and at the prescribed dosage. If other medication is being taken then advice should be sought from a doctor.
It has been reported that fish oil supplements when taken along side stimulant medication can exacerbate hyperactive behavior in some ADHD individuals. In these circumstances, the supplement should continue to be taken and the dosage of the medication be altered accordingly, under the supervision of a Doctor.
Fish oil supplements can also reduce blood clotting times and so should not be used if anti-coagulant medication is already being taken.
There is no risk attached to the ADHD diet in terms of foods chosen and the diet can be safely followed by ADHD and non-ADHD individuals alike.
Research and general acceptance
Among the specialists working in this particular field, there is a general consensus that ADHD is a disorder that involves a functional deficiency of the long-chained fats, EPA and DHA that frequently coexists with zinc and iron deficiencies. Among the wider community there remains a great deal of scepticism about ADHD and the role that diet has in its development or management.
In terms of supplementation, insufficient data is available to formulate a standardized treatment strategy and it is unclear whether the micronutrient deficiencies are a cause of, or secondary to, ADHD. Other intervention studies have looked in to carnitine supplementation and elimination diets but their findings remain inconclusive.