The ADHD diet attempts to use dietary interventions to manage attention deficit hyperactivity disorder (ADHD), a combination of inattentive, hyperactive, and impulsive behaviors that are severe, developmentally inappropriate, and impair function at home and in school. Dietary interventions for ADHD can involve supplementation with fats and some nutrients as well as avoiding certain food additives.
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 education for individuals with ADHD, making it challenging to teach them 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 ground-breaking work prompted more research studies and clinical trials designed to increase understanding of 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 in the United States 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.
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, soy, peanut, and sesame, all of which should be eaten in small amounts along with oils that are rich in ALA such as rapeseed (canola), flaxseed (linseed), and walnut oil. Olive oil, despite having a quite low ALA content, 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 in the United States still contain harmful partially 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. Seeds and nuts, including flaxseeds, walnuts, and soybeans, also contain ALA. Consequently, the food products of animals allowed to graze on open pasture will also be high in ALA, and so organic, free-range, and outdoor-reared meat, milk, and eggs are the best choices.
Fish, seafood, meat, and eggs are the best sources of EPA and DHA. 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 can 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 mg (0.5 g) 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. 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 can 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 C, vitamin E and selenium, as well as biologically active substances, such as flavonoids, anthocyanins, and carotenoids, which are found in highly colored fruits and vegetables, nuts, teas, and red wines. Vitamin C is found in citrus fruits, kiwis, and many other fruits and vegetables. Vitamin E is naturally found in PUFA-rich foods such as oils and nuts while selenium is found in fish, seafood, liver, eggs, 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.
Dietary sources of iron include red meat, fortified breakfast cereals, pulses, liver, nuts, eggs, dried fruits, poultry, fish, whole grains dark green leafy vegetables, 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; this effect is seen in children with or at high risk of deficiencies.
Foods known to be rich in zinc include seafood, liver, pine nuts, nuts, meat, cheese, 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. Some of these, particularly the colors, are unnecessary.
The following additives have been implicated in adverse reactions:
In the European Union, foods or drinks that contain sunset yellow FCF (E110), quinoline yellow (E104), carmoisine (E122), allura red (E129), tartrazine (E102), and ponceau 4R (E124) must carry on their labels the warning, “may have an adverse effect on activity and attention in children.”
The ADHD diet works by providing the right type and amount of fatty acids needed for the brain and CNS, as well as providing sufficient amounts of iron and zinc to avoid nutritional deficiencies that are associated with worsening ADHD symptoms. Nutritional supplements should be taken upon the advice of a doctor or dietitian and in addition to a healthy, balanced diet. Dietary provision of antioxidants is needed to protect the long-chain fatty acids from breakdown, which can affect brain structure and compromise signaling 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.
Dietary approaches to ADHD attempt to provide the correct types of foods needed to support the nutritional requirements of both the brain and body. An effective dietary approach could support other treatment strategies, including stimulant medication, and help 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 manufacturer's instructions and at the prescribed dosage. If other medication is being taken, advice should be sought from a doctor. Getting children to adhere to the diet may be difficult, especially for picky eaters, and the oily fish and supplements can be expensive.
It has been reported that fish oil supplements, when taken along with stimulant medication, can exacerbate hyperactive behavior in some individuals with ADHD. In these circumstances, the patient should consult a doctor to determine the correct balance of supplementation and medication.
Fish oil supplements can also reduce blood clotting time and 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 consumed, unless an individual is allergic to any of the food choices, and the diet can be safely followed by ADHD and non-ADHD individuals alike.
There is considerable interest in finding a nonmedical solution to this debilitating problem. Many parents of children with ADHD insist that dietary interventions help their children, yet the wider community has expressed skepticism about the role that diet has in ADHD development or management.
Specialists have conducted many studies attempting to prove that ADHD is caused by functional deficiency of the long-chain fatty acids EPA and DHA that frequently coexist with zinc and iron deficiencies. Results have not been universally promising. A study published in 2014 found that supplementation with omega-3 fatty acids increased working memory function but had no effect on other cognitive measures or behavior. A 2017 literature review found no clear evidence that nutrient-based interventions were useful, but it suggested that integrating diet and other lifestyle measures might be promising. Another review concluded that supplementing with PUFA was unlikely to contribute to ADHD treatment.
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 investigated the role of carnitine supplementation and elimination diets, but their findings remain inconclusive.
See also Antioxidants ; Elimination diets ; Fats ; Food additives ; Food sensitivities ; Gluten-free diet ; Hyperactivity ; Iron ; Omega-3 and omega-6 fatty acids ; Vitamin C ; Vitamin E ; Zinc .
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Emma Mills, RD
Revised by Amy Hackney Blackwell, PhD