Attention deficit hyperactivity disorder (ADHD) is defined as the combination of inattentive, hyperactive, and impulsive behaviors that 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. Individuals with ADHD are also more likely to have been of low birth weight and to have allergies or autoimmune 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. The main focus of research and therapy 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 an individual’s 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 can reduce overall quality of life for all involved.
In 1981, two British researchers, I. Colquhoun and S. 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, and dry hair and skin. These authors were the first authorities to propose that fatty acid deficiency may be a factor in ADHD. Their groundbreaking 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, dyslexia, dyspraxia, autism, depression, and schizophrenia—may involve deficiencies of certain long-chain fatty acids, 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 of ADHD. The two fatty acids 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, that perform numerous regulatory functions in the brain and body. DHA is a major building block of brain and neuronal membranes and has a profound influence on cell signaling. Both EPA and DHA are components of 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 intake of ALA and high intake of omega-6 fatty acids, saturated fat, or hydrogenated fats, 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. Children with ADHD are often found to have iron and zinc deficiencies, 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.Fats
In order to avoid a functional deficiency of these important fats, the diet should have a smaller ratio of the omega-6 essential fatty acid, linoleic acid (LA) to omega-3 essential fat (ALA), at an ideal ratio of no more than 5:1. The diet should also include 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 adequate 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 a quite 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. 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, and 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 choices.
When it comes to sources of EPA and DHA, fish and seafood are the best sources. Oily fish, such as salmon, trout, mackerel, sardines, herring, and anchovies, are especially rich in these fatty acids. 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. These foods should be incorporated into the diet regularly, unless taking a nutritional supplement that contains vitamin A, in which case a person should not eat liver or foods containing liver such as pâté.
A general recommendation of a combined daily dose of 500 milligrams (0.5 grams) EPA and DHA is needed to avoid functional deficiency of these important fats, although individuals with ADHD may have an even higher requirement. This weekly total of 3,500 mg (3.5 g) is the equivalent of about three portions of salmon every week. In the United Kingdom, the recommended number of servings per week for girls and women of childbearing age is two, and for boys, men, and women past childbearing age is four. The relative amounts of EPA and DHA vary greatly between varieties of fish, with mackerel providing 2,700 mg (2.7 g) per average portion and haddock providing a much lower 170 mg (0.17 g) for a medium sized fillet. For many people, this variability in EPA and DHA intake is unlikely to have significant consequences as long as fish is regularly consumed, but for individuals with ADHD it may compromise brain function. For this reason, pure fish oil supplements that provide a daily standard dose of EPA and DHA are useful in addition to a diet containing fish and seafood. Increasing evidence from clinical trials has indeed shown that supplementation with EPA and DHA alleviate ADHD-related symptoms in some children. These supplements also have the advantage of being relatively safe and offering general health benefits, specifically in terms of cardiovascular protection. Although pure fish oil supplements may be beneficial in some individuals with ADHD, it is important to note that more research needs to be done to fully establish the durability of any treatment effects as well as optimal dosages and formulations.
If intakes of long-chain polyunsaturated fatty acids (PUFAs), such as EPA and DHA, increase, then so does the risk of lipid peroxidation by the action of harmful free radicals. Free radicals are unstable molecules that are created during normal bodily processes such as breathing and metabolism. The body is able to maintain a balance against the negative effects of free radicals in small amounts; however, they are also produced in response to stress or environmental toxins, such as smoking and pollution. PUFAs are highly susceptible to attacks from these reactive substances and need the protection of antioxidants to avoid damage. 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, which are found in highly colored fruits and vegetables, nuts, teas, and red wines. Vitamin E is naturally found in PUFA-rich foods such as oils and nuts while selenium is found in fish, seafood, liver, egg, brazil nuts, mushrooms, and lentils. Eating the recommended daily minimum of five 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. 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-socialization symptoms.
Foods known to be rich in zinc include seafood, liver, pine nuts, cashew nuts, and whole-grain cereals, and should be eaten regularly to help avoid deficiency.
Certain synthetic food colorings, flavorings, and preservatives have been linked to increased 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 toward children.
The following additives have been implicated in adverse reactions:
- tartrazine (E102)
- quinoline yellow (E104)
- yellow 2G (E107)
- sunset yellow (E110)
- azorubine (E122)
- amaranth (E123)
- ponceau 4R (E124)
- indigotine (E133)
- green S (E142)
- caramel (E150)
- brilliant black BN (E151)
- brown FK (E154)
- brown HT (E155)
- lithol rubine BK (E180)
- benzoic acid (E210)
- sodium benzoate (E211)
- sulfur dioxide (E220)
- sodium sulfite (E221)
- sodium hydrogen sulfite (E222)
- sodium metabisulfite (E223)
- potassium metabisulfite (E224)
- calcium sulfite (E226)
- calcium hydrogen sulfite (E227)
- potassium hydrogen sulfite (E228)