Diet and nutrition for ADHD

As early as the 1970s, ADHD was considered by some to be the result of food or food additive intolerance or allergy and was treated accordingly.

One large study showed that ADHD is not the result of unhealthy food, but that unhealthy food intake is the result of ADHD.² Another study also found that ADHD sufferers more often choose unhealthy foods.³
One review found a significant correlation between typical diet and ADHD, with a “Western diet” more likely to correlate with ADHD. A “healthy” dietary pattern with plenty of vegetables, fruits, legumes, and fish correlated with up to a 37% decrease in the likelihood of ADHD. A “junk food” pattern with sweetened beverages and desserts and the “Western” dietary pattern with red meat, refined grains, processed meat, and hydrogenated fat correlated with an increased likelihood of ADHD-HI by up to 37%.⁴ The study does not neatly differentiate between correlation and causation. Causality could only come from predetermined dietary patterns and measuring their effect on symptomatology. However, only the typical eating habits of ADHD sufferers and non-affected persons were measured. It is well known that stress shifts dietary preference to fast-digesting foods. Therefore, the study may only report on consequences of ADHD.
If ADHD could be influenced so significantly with a healthy diet, word would have spread long ago. Regrettably, the effects of dietary change on ADHD symptoms are considerably smaller than the effect of ADHD on the choice of preferred diet
One review found that dieting for ADHD is not a promising treatment option for ADHD.⁵ The achievable effect sizes on symptom improvement through diets (alone) are clearly too low. For a part of ADHD sufferers - individually different - certain substances can be defined that contribute to an increase of stress/ADHD symptoms in them and whose elimination can contribute to symptom improvement. As an element of an overall treatment, this then also makes sense.
Unfortunately, the effort required to determine whether a sufferer benefits from symptom improvements is high. Moreover, only a small proportion (25-50%) of sufferers benefit, and the degree of improvement lags far behind that of other treatments.

Nevertheless, there are individual influences of food on the stress systems and vice versa of stress on the digestive organs. These can make a complementary contribution to the treatment of ADHD. The hope of successfully treating an existing ADHD through nutrition alone, however, is an illusion.

Early or prolonged stress can impair the barrier function of the intestinal mucosa and thus promote chronic intestinal inflammation.⁶
During stress, the sympathetic nervous system (activating part of the autonomic nervous system that intervenes early during stress) promotes the production of proinflammatory (pro-inflammatory) cytokines (inflammatory proteins or T-helper type 1 cytokines, e.g. tumor necrosis factor alpha, interleukin IL-1, IL-2 and IL-12, interferon gamma), which are, however, only beneficial in the short term. If they are active for too long (due to prolonged stress), they attack cells and tissues, which, in addition to degeneration of cells (cancer) and damage to the immune system, can lead to chronic inflammatory bowel disease. An intestinal wall damaged by inflammatory processes restricts the absorption of vital substances. To temporally limit the effect of proinflammatory cytokines, cortisol released by the HPA axis (intervening late during stress) has an inhibitory effect on proinflammatory cytokines and promotes anti-inflammatory (anti-inflammatory) cytokines (T-helper type 2 cytokines, e.g., interleukin IL-4, IL-5, IL-6, and IL-10). TH-2 cytokines repel extracellular pathogens (bacteria, parasites) and promote basophils, mast cells, and eosinophils, which can promote allergies if they are excessive.
Thus, a disturbance in the balance of the HPA axis (hypocortisolism = too little cortisol or hypercortisolism = too much cortisol) can lead to an imbalance between immune responses and promote inflammation or allergies.⁷
If these inflammations or allergies affect the digestive system, food intolerances are an obvious consequence. See 1.14. and 1.18. below.

Further, stress can alter the expression of genes, including those responsible for providing enzymes in the digestive tract.

Gut failure correlated with certain increased ADHD symptoms in elementary school students.⁸

In our opinion, in cases of a known food intolerance, an appropriate diet could form a thoroughly relevant complementary contribution to the treatment of ADHD. However, diets are unsuitable as a general or sole treatment method for ADHD. The effect size of successful diets (in the presence of food intolerance) is with 0.25 so significantly below that of medication (up to 1.1) that a sole diet treatment corresponds to a partial non-treatment.
⇒ Effect size of different forms of treatment for ADHD

• 1. ADHD as a dietary consequence / food intolerance
  • 1.1. Food / dietary supplements with influence on ADHD
    • 1.1.1. Polyunsaturated fatty acids (PUFAs)
    • 1.1.2. Food intolerances
      • 1.1.2.1. Elimination diet - (conditionally) effective, but difficult
        • 1.1.2.1.1. Individual studies on elimination diets
        • 1.1.2.1.2. Dutch elimination diet protocol (Few food diet, FFD; RED)
      • 1.1.2.2. Frequently incompatible foods
        • 1.1.2.2.1. Often incompatible according to studies on elimination diets for ADHD
        • 1.1.2.2.2. Sugar
        • 1.1.2.2.2.1. Sugar as a food intolerance in ADHD
        • 1.1.2.2.2.1. Sugar and EEG
        • 1.1.2.2.3. Milk protein/milk casein, lactose
        • 1.1.2.2.4. Gluten intolerance in ADHD
        • 1.1.2.2.5. Dyes
        • 1.1.2.2.6. Preservatives
        • 1.1.2.2.6.1. Sodium benzoate (E 211)
        • 1.1.2.2.6.2. Sodium nitrite (sodium nitrit)
        • 1.1.2.2.7. Flavor enhancer
        • 1.1.2.2.7.1. Monosodium glutamate (L-sodium glutamate)
      • 1.1.2.3. Practical and social problems with diets for ADHD
      • 1.1.2.4. Subjective overestimation of dietary therapies
  • 1.2. Food (supplement) with possible influence on ADHD
    • 1.2.1. Low-density lipoprotein
    • 1.2.2. Saturated fatty acids
    • 1.2.3. Inorganic phosphorus
    • 1.2.4. Salt
    • 1.2.5. Tetrahydroisoquinolines / Tetrahydroisoquinolines (TIQ)
  • 1.3. Food (supplements) without evidence of influence on ADHD
    • 1.3.1. Ketogenic diet
    • 1.3.2. Mediterranean diet
    • 1.3.3. Exorphins (no evidence verifiable)
    • 1.3.4. Sweetener
    • 1.3.5. Trans fats (no evidence verifiable)
  • 1.4. Food (supplement) without influence on ADHD
    • 1.4.1. Phosphate incompatibility (refuted)
    • 1.4.2. Salicylates (fine gold; refuted)
• 2. Other nutrition-specific treatment approaches for ADHD
  • 2.1. Desensitization of food intolerances
  • 2.2. Probiotic treatment can influence behavior
  • 2.3. Increased intestinal permeability in ADHD
• 3. Further literature

1. ADHD as a dietary consequence / food intolerance¶

People who have a predisposition to a disorder, but who have it at a level of intensity that is not yet pathological without additional stresses, are healthy.
However, if a strain on the stress systems occurs in your case, the disturbance pattern can become so energetic that it leaves the realm of the healthy and can become disturbing.
Others, however, who are further away from the unhealthy intensity of disturbance by disposition, do not mind the additional stressor. This can be called resilience.

Once an unhealthy range has been reached, it can be left again by eliminating the most recently added stressor - or by eliminating other stressors that have existed for some time, only at a time when not so many stressors converged that an unhealthy level was reached.

With this picture, it may become more understandable what influences different forms of treatment can have. The elimination of a food intolerance or an allergy, the change to a healthy diet or the elimination of vitamin deficiencies may possibly be just sufficient for a weaker form of a disorder to leave the unhealthy stress range again and to lead it just below the “pathological” range. Whether this is sufficient for the affected person or whether a stronger treatment, which not only brings the symptoms just below the “diagnostic” level, but also reduces the symptoms more clearly into the healthy range, is not more helpful, must be decided in each individual case.
Strong disturbance manifestations are in any case only treatable with medication and additional non-drug therapeutic measures. However, even in these cases, the elimination of an existing food intolerance is just as helpful a support as the elimination of other stressors.

Once again, it is important to warn against the idea that ADHD so severe that the affected person regularly has difficulties in school or at work can be treated with a change in diet alone. The considerable effort that must be made by the whole family often leads to a false evaluation (bias: “we have done so much, this must now simply help”).
The effect size of symptom improvement by eliminating a (actually existing) food intolerance is about 0.25 and cannot be compared with the effect size of medication (up to 1.1).
ADHD is not a banality. Several very large studies found an increase in premature mortality of about 1.5 percentage points with untreated ADHD. Untreated ADHD increases the risk of addiction many times over. The rate of ADHD in male prisons is about 8-fold that of the rest of the population. ⇒ Consequences

1.1. Food / dietary supplements with influence on ADHD¶

1.1.1. Polyunsaturated fatty acids (PUFAs)¶

Polyunsaturated Fatty Acids (PUFAs)
Other names: n-3 fatty acids, n-6 fatty acids, omega-3/omega-6 fatty acids.

PUFAs are:

• Docosahexaenoic acid (DHA)
• Eicosapentaenoic acid (EPA)
• Arachidonic acid (AA)
• Alpha-linolenic acid (ALA)
• Linoleic acid (LA)

N-3 fatty acids are:

• Docosahexaenoic acid (DHA)⁹
• Eicosapentaenoic acid (EPA)⁹
• Alpha-linolenic acid (ALA)⁹
• Eicosapentaenoic acid (EPA)⁹

N-6 fatty acids are:

• Arachidonic acid (AA)⁹
• Linoleic acid (LA)⁹
• Gamma-linolenic acid (GLA)⁹

Several meta-analyses show a weak (although statistically significant) contribution of PUFA fatty acid supplementation to ADHD symptom improvement,^{1011 12} as does a recent small placebo-controlled trial.¹³¹⁴

One study found lower levels of arachidonic acid in children with ADHD.¹⁵

Possible symptoms of PUFA deficiency include:¹⁶⁹

• Polydispia (excessive feeling of thirst)
• Polyuria (excessive urine output)
• Dry hair
• Skin and follicular keratosis (rubbing skin, white or red pimples up to the size of a pin, similar to goose bumps, on upper arms, thighs, buttocks, face)
• Scaling

A Japanese study found significantly decreased blood plasma levels of polyunsaturated fatty acids in 24 ADHD sufferers under 20 years of age¹⁷

• Docosahexaenoic acid (DHA)
• Eicosapentaenoic acid (EPA) and
• Arachidonic acid (AA)

With respect to DHA, a placebo-controlled study over 6 months in 50 school-aged children with ADHD found no significant improvement in ADHD symptoms.¹⁸ Nevertheless, small improvements in behavioral problems and cognitive difficulties were reported. Other studies sometimes confirmed an effect of DHA in ADHD, and at other times found no benefit.¹⁹

A diet rich in fish for the mother during (especially early) pregnancy correlated with lower attention problems in the children. In contrast, the proportion of fish in the children’s diet had no influence. Fish contains many PUFAs.²⁰

A randomized study of 75 children and adolescents that ran for 3 months placebo-controlled and another 3 months with omega 3/6 administration to all participants found a reduction in ADHD-HI symptoms of with more than 25% in 26% of participants. In the no longer placebo-controlled portion, the rate of improvement increased to 47% of participants at 6 months. Responders were more often of the inattentive subtype and had comorbid neurodevelopmental disorders. Symptom ratings were made by the authors.²¹

Another placebo-controlled study found improvements in behavior with omega-3 administration after 3 months, while there was no improvement in cognitive performance (attention) even after 6 months.²²

A study of (only 18) children with ADHD suggests a possible improvement in heart rate variability with omega-3.²³²⁴

Another study found that children with ADHD ate significantly fewer foods containing omega-3 fatty acids than the comparison group.²⁵

A double-blind placebo study found no difference in ADHD symptomatology between children receiving MPH and placebo and children receiving MPH and omega-3.²⁶

A large study of 432 children found a significantly increased serum omega-6 to omega-3 ratio in children with ADHD.²⁷ This correlated with an increased intake of nutrient-poor foods such as high-sugar and high-fat foods and a decreased intake of vegetables, fruits and protein-rich foods than in healthy children
A diet high in sugar and fat has been associated with increased levels of inflammation in the PFC and liver problems, as well as behavioral changes discussed in the context of ADHD.²⁸
It is an open question whether the altered diet is the cause, consequence, or vicious cycle of ADHD.

Rats whose mothers were fed a diet low in omega-3 (DHA) during pregnancy showed increased reactivity of the HPA axis and increased anxiety and depression symptoms as adults.²⁹

A 12-week, double-blind, placebo-controlled study examined the relationship between baseline PUFAs levels and the effect of high-dose eicosapentaenoic acid (EPA, 1.2 g) in n = 92 adolescents (6-18 years) with ADHD. Compared with the placebo group, the EPA group showed³⁰

• Improved focused attention: effect size 0.38
  • In all EPA-treated patients
• Improved hit response time: effect size 0.89
  • Only among EPA-treated individuals with the lowest baseline EPA levels
• Vigilance (HRT interstimulus interval changes, HRTISIC): Effect size 0.83
  • Only among EPA-treated individuals with the lowest baseline EPA levels
• Weaker improvement in impulsivity (commission errors) than the placebo group
  • In all EPA-treated patients
• Lower improvements in other ADHD symptoms and emotional symptoms than the placebo group
  • Only among EPA-treated individuals with the highest baseline EPA levels
• Increased blood EPA level by 1.6 times
• Unchanged:
  • Blood DHA level
  • Hs-CRP level
  • BDNF plasma levels

An 8-week course of DHA in children with ADHD was reported to have produced a slight improvement in impulsivity in one study.³¹

1.1.2. Food intolerances¶

Individual food intolerances or allergies are just as much stressors as diseases, toxins or psychological stress and can therefore worsen the stress situation of affected individuals to such an extent that symptoms develop. This is not an ADHD-specific finding, but is based on more general mechanisms.³²

Food intolerances are nevertheless not the (singular) cause of schizophrenia, psychoses or ADHD. However, food intolerances can, in our understanding, exacerbate any form of mental disorder.
All mental disorders are “only” the extreme forms of a corresponding predisposition. In other words, almost all mental disorders are dimensional, i.e. determined by the degree of the disorder, not categorical, such as pregnant/not pregnant. Mental disorders are generally accompanied by a serious imbalance in stress regulatory systems. Therefore, influences that put additional stress on the stress systems can reinforce a predisposition to a mental disorder in such a way that it is precisely this last additional influence that causes it to reach a disturbing (pathological) level.

1.1.2.1. Elimination diet - (conditionally) effective, but difficult¶

In an oligoantigenic diet, the diet is initially changed to a low irritant and most likely non-symptomatic diet for 3 weeks. Typically, the diet is restricted to rice, vegetables, and meat, and water as a beverage. Provided this diet reduces symptoms after several weeks (which is highly suggestive of food intolerance or allergy), one (more) food is then reintroduced into the diet every 5 days and remains if there has been reliably no symptom return.

Egger³⁶ describes such a diet with which behavioral improvements can be achieved to an appreciable extent. Egger himself describes this elimination diet (which he calls an oligoantigenic diet) as effective for some sufferers, but very demanding to implement. Other authors in the same work believe that an (oligoantigenic) elimination diet can hardly be implemented in daily life.³⁷

Quite a few studies have found improvements with diets, however, in reviews through testing compared to drug and psychotherapeutic treatment

• Significantly fewer sufferers show improvement
  and also a
• Significantly weaker decrease in ADHD symptoms was detectable.

For the report of a sufferer of the effort and effect of a (in the result probably oligoantigenic) diet see below.

The fact that these diets treat food intolerances rather than food allergies is evident from the fact that the interfering substances found by means of the elimination diet were not conspicuous in blood tests by elevated IgG and IgE antibodies. Conversely, the substances for which IgG and IgE antibodies were elevated were not always those that increased ADHD symptoms.³⁸³⁹

1.1.2.1.1. Individual studies on elimination diets¶

• A meta-analysis reported an effect size of 0.51 to 0.8 for the elimination diet⁴⁰
• One of the first and oldest studies reported that an oligoantigen elimination diet produced complete elimination of ADHD symptoms in 21 of 76 hyperactive children and improvements in symptoms in another 41. fourteen children (18.5%) did not benefit. In 28 of the children with improvements, eliminated foods were added back to the diet (randomized, double-blind, placebo-controlled), each of which significantly increased or decreased symptoms more often than placebo.⁴¹
• Coloring agents and preservatives were the most frequently eliminated foods, but never the sole triggers. This is consistent with the results of the meta-analysis by Nigg et al. who found an effect size of 0.29 for elimination diets versus an effect size of 0.12 to 0.25 for dietary supplements.⁴²
• A very similar study found symptom improvements in 59 of 78 children, but all below the level of drug treatment. Substances that had already been eliminated, when administered in a double-blind masked fashion, increased symptoms again in 19 of 23 subjects. However, these are only parent ratings.⁴³
• A smaller study of 26 affected children showed that 19 children (73%) responded positively to an elimination diet, with all responding to quite a few foods, dyes, and/or preservatives. A double-blind, placebo-controlled review in 16 children showed significant differences between placebo and exposure. Children with allergic tendencies responded significantly more sensitively than the non-atopic group.⁴⁴
  Our understanding is that allergies are typical in ADHD-I subtype, whereas inflammation is more typical in ADHD-HI (with hyperactivity).
• Another study reported a positive effect of an elimination diet in some of the ADHD sufferers. On average, 5 (individually different) foods were found to be eliminated per child.⁴⁵⁴⁶
• A fairly small study found good improvements with an elimination diet in parent and teacher ratings.⁴⁷
• Another small study that included objective tests in addition to assessments found good results in subjective assessment, but these were not confirmed in objective tests.⁴⁸
• A double-blind study of 100 children demonstrated good efficacy of an elimination diet, with a subsequent diet that selected for IgG levels alone (which mark allergies) showing symptom exacerbations in 63% of participants.³⁹
• In 49 hospitalized children, a crossover/double-blind/placebo-controlled study in Mannheim compared the efficacy of an oligoantigen elimination diet with that of medication with methylphenidate. While the responder rates for methylphenidate were almost twice as high (44%) as for elimination diet (24%), the symptom improvements were almost equal.⁴⁹
  In this regard, it should be noted:
  • A responder rate of 44% to methylphenidate is very low. The usual rate is 70%, although this can be increased to 85-90% by switching nonresponders to amphetamine medication.
  • An elimination diet is likely to be easier to adhere to in an inpatient hospital setting than in everyday life.
• A nonstrict elimination diet was positively evaluated in parent-only reports.⁵⁰
• A small study found subjects on an oligoantigenic diet still improved from pre-diet ADHD status after 3.5 years⁵¹
• Deficiencies in certain vitamins and minerals are a risk of elimination diets.⁵²

Problematic in the evaluation of diets in ADHD is that the results are subjectively significantly overestimated by parents in parent questionnaires. Objective tests show much weaker improvements. For more on this, see below.

The UK’s National Institute for Health and Care Excellence (NICE) currently sees more disadvantages than advantages to elimination diets in 4- to 8-year-olds.⁵³

1.1.2.1.2. Dutch elimination diet protocol (Few food diet, FFD; RED)¶

In the Netherlands, a specific strict protocol is used for testing an elimination diet in children with ADHD.⁵⁴

• Verification that the family and child meet the participation criteria

• Inventory of family history, family situation, child’s medical background, baseline assessment of child’s behavior

• Two-week baseline period

  • Child retains his usual diet
  • Discontinuation of nutritional supplements (e.g. fish oil, vitamins)
  • Retention of psychoactive medications
  • Parents keep diary of child’s daily activities, eating habits, medications and behavior

• Renewed behavioral measurements at the end of the baseline period

• Parents receive detailed training on possible pitfalls in adhering to the FFD, based on the information provided by the diary. Parents are urged to also follow the elimination diet (omit all foods that are not allowed during elimination diet) to optimally support the child. Parents are provided with a schematic overview of which foods are allowed in which quantities and on which days.

• 1 week transition to elimination diet

  • Gradual adaptation of the child’s diet to the extended elimination diet

• 2 weeks extended elimination diet (FFD, RED)
  Allowed are:

  • All foods of the strict FFD
  • Additionally small portions of certain foods:
    • Wheat (daily)
    • Lamb (daily)
    • Butter (daily)
    • Corn (twice a week)
    • Potatoes (twice a week)
    • Pear spread (twice a week)
    • Mango (twice a week)
    • Honey (twice a week)
  • If relevant behavioral improvement: continuation of extended FFD

• If no behavioral improvement from extended FFD
  gradual restriction of diet to strict FFD for then another 2 weeks

  • Rice
  • Turkey
  • Vegetables
    • Cabbage (white, green, Chinese, red)
    • Beets
    • Cauliflower
    • Kale
    • Rutabagas
    • Sprouts
    • Salad
  • Pear
  • Olive oil
  • Ghee (similar to clarified butter)
  • Salt
  • Rice drink with added calcium

• (relevant) behavioral improvement is observed (responder)

  • Psychotropic drugs are discontinued

• No improvement in behavior is observed (nonresponder)

  • Further adjustment of the diet

• Repeat behavioral measurements at the end of the FFD

• In responders, individual foods that had previously been excluded are then reintegrated into the diet.

  • If there is no deterioration in behavior after several days of consumption, food can be consumed again without hesitation
  • If behavioral deterioration results, food is permanently banned from diet

One study reported that 60% of the 54 participating children showed behavioral improvements of 40% or more, but only 14 of 54 children maintained the diet for more than 6 months because of successful behavioral improvement.⁵⁴

1.1.2.2. Frequently incompatible foods¶

1.1.2.2.1. Often incompatible according to studies on elimination diets for ADHD¶

Studies of elimination diets report the following foods frequently triggering symptoms. Percentages are for those (out of less than 100) subjects in whom the food was responsible for symptoms. Because of the small number of subjects, the results are highly uncertain.

• Food additives (79%)⁵⁵, (70%)⁴³
• Chocolate (64%)⁴³, (59%)⁵⁶
  • See also below Tetrahydroisoquinoline / Tetrahydroisoquinoline (TIQ)
• Cow’s milk (64 %)⁵⁷⁴³
• Oranges (57%)⁴³
• Grapes (50%)⁵⁷
• Wheat (49%)⁵⁷, (45%)⁴³
• Cow’s milk cheese (45%)⁴³, (40%)⁵⁶
• Citrus (45%)⁵⁶
• other fruit (36 %)⁴³
• Eggs (39%)⁵⁶ to (18%)⁴³
• Peanuts (32 %)⁵⁶
• Corn (29 %)⁵⁶
• Fish (23 %)⁵⁶
• Oats (23 %)⁵⁶
• Melons (21%)⁵⁶
• Tomatoes (22%)⁴³, (20%)⁵⁶
• Pineapple (19%)⁵⁶
• Sugar (16 %)⁵⁶
• Beef (16 %)⁵⁶
• Beans (15%)⁵⁶
• Peas (15%)⁵⁶
• Malt (15 %)⁵⁶
• Apple (13 %)⁵⁶
• Pork (13 %)⁵⁶
• Pears (12 %)⁵⁶
• Chicken (11 %)⁵⁶
• Potatoes (11 %)⁵⁶
• Tea (10 %)⁵⁶
• Coffee (10 %)⁵⁶
• mixed nuts (10 %)⁵⁶
• Cucumbers (9%)⁵⁶
• Bananas (8%)⁵⁶
• Peach (7%)⁵⁶
• Carrots (7%)⁵⁶
• Lamb (5%)⁵⁶
• Turkey (5%)⁵⁶
• Rice (4 %)⁵⁶
• Yeast (4 %)⁵⁶
• Apricots (3%)⁵⁶
• Onions (3 %)⁵⁶

1.1.2.2.2. Sugar¶

1.1.2.2.2.1. Sugar as a food intolerance in ADHD¶

Sugar is a possible ADHD trigger in the oligoantigenic diet (1.1.).

A diet that limited sugar and excluded caffeine, chocolate, food additives, artificial colors, glutamate, and, for each child individually, potentially allergenic foods (such as milk) produced significant behavioral improvement in 45% of the participating children, including improvement in sleep problems phenotypic of ADHD (including delay in falling asleep).⁵⁰
In a parallel diary study, 15% of participating children (regardless of ADHD status) were found to have associations between their food consumption and behavior.⁵⁸
In our view, these observations correlate with Egger’s results.

One study tested urinary sugar excretion in children with and without ADHD on identical diets. The ADHD sufferers were found to have unusually elevated levels of:⁵⁹

• Fructose (in 52.5% of ADHD sufferers)
• Maltose (at 65 %)
• Galactose (at 75%)
• Lactose (at 95%).

In addition, all 40 affected persons were found to be

• Glycosaminoglycans (mucopolysaccharides) (at 100%) in the pathological range

The authors consider this to support the hypothesis that ADHD is associated with aberrant carbohydrate metabolism.

One study found a correlation between sugar intake at 30 months and risk for ADHD, sleep disorders and anxiety. No correlation was found at 12 months of age.⁶¹
Whether this is a causal cause or a consequence of altered food preferences due to the disorder predisposition is an open question.

(Real) sugar is thought to lower the cortisol response to stress triggers.⁶² This could result in a negative effect of sugar on stress resistance in hypocortisolism (ADHD-HI: with hyperactivity). This is likely to be particularly relevant in ADHD-HI and ADHD-C sufferers, who often have a reduced cortisol response to stressors (in contrast to ADHD-I sufferers). ⇒ The subtypes of ADHD: ADHD-HI, ADHD-I, SCT, and others

Experience shows that a low cortisol stress response is often accompanied by a low alpha-amylase response. Alpha-amylase is an enzyme in the intestine responsible for breaking down carbohydrates into sugar. This could be a link between stress and eating problems or obesity and could be seen as an indication of poorer sugar conversion in the presence of a reduced cortisol stress response. More information is needed to verify this idea.

Glucose administration stimulated an increase in blood epinephrine levels in a fairly small group of subjects (n = 28), which were almost 50% lower in ADHD than in unaffected subjects. Plasma norepinephrine levels were also lower in ADHD than in unaffected subjects. These data suggest a general impairment in sympathetic activation as well as regulation of catecholamines (dopamine, norepinephrine, serotonin) in ADHD.⁶³

A diet high in sugar and fat has been associated with increased levels of inflammation in the PFC and liver problems, as well as behavioral changes discussed in the context of ADHD.²⁸

Children and adolescents with ADHD consume sweets and fruit gums more frequently and more than healthy controls. It is unclear whether this is a cause or consequence of ADHD.⁶⁴

That sugar is not per se a trigger of ADHD is shown by a study that compared the sugar consumption of 6- to 11-year-olds with their development of possible ADHD. No correlation was found. This supports the view that sugar is not a universal trigger of ADHD, but does not rule out the possibility that sugar intolerance may promote ADHD.⁶⁵ Another report comes to the same conclusion, but points out that sugar increases adrenaline synthesis.⁶⁶

1.1.2.2.2.1. Sugar and EEG¶

In a single-case study that we supervised, the changes in EEG caused by sugar were observed in an affected person in whom sugar caused ADHD-HI symptom intensifications:

• Sugar (2 candy bars within 5 minutes at 90 kg body weight) caused significant changes in the EEG of an ADHD-HI subject (with hyperactivity) in neurofeedback.
  • Within 10 minutes, Beta1 increased significantly.
    The threshold values during theta up / beta down training had to be reduced considerably. The 85% of target values reached before sugar intake had dropped to 50%. This means that the ability to relax had decreased drastically.
  • After 20 minutes, all values (theta, alpha, beta1, beta 2, hi-beta) were significantly reduced. Relatively speaking, however, Beta 1 was now well above SMR. Beta1 should be below SMR, so SMR training aimed at increasing SMR is the first step of neurofeedback treatment of ADHD.
  • After 30 minutes, Beta1 had caught up somewhat with SMR. Hi-Beta was now significantly higher.

Problematic in the evaluation of diets for ADHD is that the results are subjectively significantly overestimated by parents. Objective tests show much weaker improvements. More on this below under 3.

1.1.2.2.3. Milk protein/milk casein, lactose¶

Proteins and peptides can enter the bloodstream directly from food via the intestine.

Inhibition of certain peptidases or genetically reduced peptidase activity (= a protein intolerance, which is to be distinguished from an allergy) causes increased absorption of peptides from the intestine into the bloodstream. The peptides accumulate and are excreted in increased amounts in the urine (peptiduria). Elevated urinary peptide levels therefore indicate genetic, epigenetic, or toxic impairment of key enzymes involved in peptide cleavage. Elevated levels of bioactive peptides in urine have been found in schizophrenia, depression, autism, and ADHD.⁶⁷

In the study of 104 children with ADHD and 36 unaffected children, not only did the ADHD sufferers clearly differ according to peptide levels in the urine. The type of peptides found also clearly differentiated the ADHD subtype:⁶⁸

• Sixty-four sufferers with the ADHD-HI subtype (with hyperactivity) showed elevated benzoic acid-glycoprotein-peptide complexes.
• 35 affected individuals (all but 3 of whom corresponded to the ADHD-I subtype without hyperactivity) showed reduced levels of uric acid complexes.
• 5 affected individuals (4 of whom were hyperactive) showed reduced amounts of all urinary complexes.
• Urinary peptides of hyperactive sufferers increased the uptake of serotonin in platelets.⁶⁹

Unfortunately, there are hardly any other studies on peptides in urine in mental disorders - not even any that have refuted this thesis.

Proteins (proteins) in urine can be a symptom of emotional stress, among other things.⁷² An examination of the urine of 15 pet dogs and 20 shelter dogs revealed significantly elevated peptide levels in the urine of the shelter dogs.⁷³

However, if a dairy- and casein-free diet were a successful solution for ADHD, this treatment should have become established long ago. As the studies on elimination diets show, the triggering foods are highly individual and therefore cannot be identified as a group across the board.
In the context of an oligoantigenic diet, dairy products are also to be tested. Dairy products (especially cow’s milk products) were often, but by no means always, eliminated.

Surprisingly, there is hardly any literature on the influence of lactose intolerance on ADHD.

1.1.2.2.4. Gluten intolerance in ADHD¶

Gluten can be a factor in ADHD, but is not “the” cause of ADHD.

Of 67 children with ADHD examined, 10 were found to be gluten intolerant.³³ Since only 0.6 to 0.8% of the entire population is affected by celiac disease, this would be about 20 times more common
Conversely, children with celiac disease had an ADHD prevalence of 16%, more than twice the prevalence expected without celiac disease.⁸⁰

There is evidence that the risk of serious mental disorders increases approximately fourfold in celiac disease.⁸¹ A gluten- and casein-free diet reportedly showed reduced ASD-associated gastrointestinal symptoms and improvements in antisocial behavior in a study of a brand-name ASD.⁸² Both gluten-free and ketogenic diets may affect the gut microbiome.⁸³

These results are not robust due to the small number of studies and subjects.
However, in the context of an elimination diet (see above), wheat is often identified as the triggering food.

1.1.2.2.5. Dyes¶

Feingold’s original study results, according to which a diet without dyes and food additives could reduce ADHD symptoms such as hyperactivity, were put into perspective by later, methodologically more complex studies.⁸⁴

A meta-analysis shows a weak to moderate significant contribution of dietary dye exclusion to ADHD symptom improvement, especially in those with food intolerance.¹⁰⁸⁵
The authors of a meta-analysis of 24 studies on ADHD and dyes in food concluded that about 8% of ADHD sufferers have symptoms due to dietary supplements. An effect size of 0.12 to 0.25 was found, compared to an effect size of 0.29 for elimination diets.⁸⁶⁸⁷
Another meta-analysis of randomized, double-blind (and thus largely removed from assessment bias) studies on whether dyes can trigger hyperactivity symptoms found an effect size of 0.21. When smaller, lower-quality studies were also added, this increased to 0.283.⁸⁸
It is problematic that almost all studies on dyes in ADHD are based on parent ratings, which (if not double-blind) implies a considerable bias towards an exaggeration of symptom reduction by eliminating dyes from the diet,⁸⁹ especially if the parents have to monitor the diet, since a diet causes effort, which quite regularly leads to the expectation that this effort cannot remain fruitless.
A meta-analysis of 4 studies examined blue dyes and found influences of elimination diets that avoided FDA-approved blue dyes.⁹⁰

In order to be able to judge whether the calculated effect sizes mean small or small to medium effects, one would need to know which effect size calculation method was used. See for this Effect size at Wikipedia.

On an elimination diet, dyes or preservatives were the most commonly eliminated foods, but no child responded to these alone, see above.⁴¹
A small study found that in AD(HS sufferers, dyes in the EEG correlated with an increase in posterior mean gamma power and a decrease in posterior relative alpha power. Further, a small increase in inattention symptoms was found.⁹¹

A meta-study discusses findings on dyes in autism.⁹²

See also the two studies under Preservatives / Sodium benzoate (E 211).

Foods containing the following colorants must be labeled with the statement “may impair activity and attention in children” since July 20, 2010:

• E 102 (tartrazine)
• E 104 (chilon yellow)
• E 110 (yellow orange S)
• E 122 (azorubine)
• E 129 (allura red)

Such indications always include a large margin of caution.

1.1.2.2.6. Preservatives¶

1.1.2.2.6.1. Sodium benzoate (E 211)¶

A double-blind study of 244 children on artificial colors and sodium benzoate (E 211) found a significant correlation with increased hyperactivity.⁹³

Another study of 267 healthy children also found that dyes or sodium benzoate (E 211) (or both) increased hyperactive symptoms in 3-4 year olds as in 8-9 year olds.⁹⁴ The European Food and Drug Administration had this finding evaluated by a panel of experts. After corrections to the statistical mathematical evaluation model of the study under investigation, the 53-page review concluded that the effect, if present at all, was of little clinical relevance.⁹⁵

1.1.2.2.6.2. Sodium nitrite (sodium nitrit)¶

There are no known direct studies on sodium nitrite regarding negative effects in relation to ADHD.

However, sodium nitrite is said to be potentially capable of impairing working memory.^96979899

Sodium nitrite could affect the acquisition of an inhibitory avoidance response in rats and mice through a direct effect on the CNS.¹⁰⁰

Although sodium nitrite is systematically used to cause memory problems in experimental animals to explore agents to improve memory performance, there is no study related to sodium nitrite in ADHD.

1.1.2.2.7. Flavor enhancer¶

1.1.2.2.7.1. Monosodium glutamate (L-sodium glutamate)¶

0.4 mg / kg monosodium glutamate (L-sodium glutamate) appears to induce ADHD symptoms in rats.¹⁰¹
So far, no such effect is known in humans.

1.1.2.3. Practical and social problems with diets for ADHD¶

A food diet that requires such a consistent implementation as is necessary for an oligoantigenic diet as a threshold diet (see report of the affected person there) will only be feasible in early and middle childhood in the rarest of cases. At the earliest in adolescence and only with extreme commitment of the affected person, a diet compliance with the required consistency (which is per se difficult for ADHD sufferers) is even conceivable.

The restriction of an elimination diet is unlikely to be limited to eliminating the intolerable foods alone. In addition, a consistent diet probably further requires that all unknown foods be avoided (or consistently recorded, with a new food tried for 3 days precluding the trying of any other unknown foods).
Going out to eat already is considerably more difficult, since it is usually not likely to be reliably known which foods have been used for preparation. At best, only a few dishes can be consumed without worry.
Eating at a friend’s house is more difficult for the same reasons.
The significant social limitations of those affected, in addition to the already “being different,” and the stress for those affected resulting from the further limitations, must be weighed when considering diet as a therapy for ADHD.

1.1.2.4. Subjective overestimation of dietary therapies¶

Diets are able - with considerable effort and additional social burden for sufferers - to improve ADHD symptoms in individual sufferers.

The problem is that subjective assessments of the results by parents are always far more positive than the results of objective tests.¹⁰²

Because assessment bias occurs even in double-blind studies, a substantial bias (preconception) of parents to confirm the subjectively desired outcome (that ADHD could be treated by diet rather than critically considered medication) can be assumed.
However, it is also conceivable that the parents were already enthusiastic about the small improvements brought about by an elimination diet. Due to the study designs, the parents were not allowed to know the much better effect that could be achieved by medication at the time of evaluation and therefore could not have a comparison criterion. The only criterion for comparison could therefore only be whether or not there was any improvement at all.
Furthermore, the enormous effort required for a diet in ADHD is likely to promote an expectation that this effort must pay off. It is a general psychological principle that the greater the effort expended, the more positively results are evaluated.

It is also conceivable that the decision alone to do something for oneself by means of a diet - possibly even with the experience that this does good - enables an experience of self-efficacy. This could have a healing effect in relation to the central psychological self-esteem problem, even if this effect is likely to be rather small in ADHD.

1.2. Food (supplement) with possible influence on ADHD¶

1.2.1. Low-density lipoprotein¶

In ADHD-affected children, one study found significantly elevated blood levels of total cholesterol and low-density lipoprotein (LDL), while high-density lipoprotein (HDL) and triglyceride (TG) levels did not differ from unaffected individuals.¹⁰⁴ In contrast, another study found significantly decreased blood levels of total cholesterol, high-density lipoprotein (HDL), and low-density lipoprotein (LDL) in boys with ADHD (regardless of subtype).¹⁰⁵
In adults, a large cohort study found slightly reduced low-density lipoprotein (LDL) levels.¹⁰⁶

Treatment of bipolar adults with comorbid ADHD with lisdexamfetamine (Elvanse) produced significant decreases in weight, body mass index, total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, but not triglyceroids or blood glucose levels.¹⁰⁷

A study suggests a genetic alteration of the receptor for low-density lipoprotein in ADHD.¹⁰⁸ The fact that lipoprotein metabolism is altered in ADHD was also the result of another small study.¹⁰⁹

Methylphenidate reduces low-density lipoprotein levels, among other things.¹¹⁰

Further studies on fats and fatty acids in ADHD did not lead to clear results.¹¹¹

1.2.2. Saturated fatty acids¶

A large study of 432 children found significantly higher serum levels of saturated fat in children with ADHD.²⁷ This correlated with an increased intake of nutrient-poor foods such as high-sugar and high-fat foods and a decreased intake of vegetables, fruits and protein-rich foods than healthy children. It is an open question whether the altered diet is a cause, consequence, or vicious cycle.

1.2.3. Inorganic phosphorus¶

A large study of 432 children found significantly elevated serum levels of inorganic phosphorus in children with ADHD.²⁷ This correlated with an increased intake of nutrient-poor foods such as high-sugar and high-fat foods and a decreased intake of vegetables, fruits and protein-rich foods.
It is an open question whether the altered diet is the cause, consequence, or vicious cycle of ADHD.

1.2.4. Salt¶

High salt consumption can impair cognitive abilities, but is reversible by reducing excessive salt consumption.¹¹²

Salt starvation may be an indication of aldosterone deficiency. This could be associated with pituitary or adrenal insufficiency, which are common in ADHD-HI (with hyperactivity).
Since ADHD-I is more likely to have an exaggerated endocrine stress response, a particularly high sense of thirst could be associated with elevated aldosterone levels in this case.
⇒ Aldosterone In chapter⇒ Neurological aspects

1.2.5. Tetrahydroisoquinolines / Tetrahydroisoquinolines (TIQ)¶

It was reported that 4 metabolites of TIQ (representing an aberrant degradation pathway of dopamine) were massively elevated in urine in children with ADHD.
TIQ are synthesized in the brain and also absorbed through food.
The question therefore arises as to whether there is a relationship to food intake here.¹¹³

Chocolate (cocoa) contains significant amounts of the alkaloids salsolinol (up to 2.5 mg) (1-methyl-6,7-dihydroxy-tetrahydroisoquinoline) and salsolin (1-methyl-6,-methoxy-7-hydroxy-tetrahydroisoquinoline).¹¹⁴ However, salsolonil does not appear to be blood-brain mobile.¹¹⁵

Salsolinol
- is formed in the brain from dopamine and acetaldehyde or pyruvic acid
- is an endogenous neurotoxin that causes oxidative stress and mitochondrial damage by inhibiting the electron transport chain¹¹⁶
- inhibits:¹¹⁷¹¹⁴
- Tyrosine hydrolylase
- DA-β-hydroxylase
- COMT
- MAO
- cAMP education
- ACTH
- Endorphins

1.3. Food (supplements) without evidence of influence on ADHD¶

1.3.1. Ketogenic diet¶

Ketogenic diet is based on a composition of 10% carbohydrates, 20% protein, 70% good fats (no trans fats). As long as no dietary mistakes are made (too much carbohydrates), this leads to a conversion of energy metabolism in the liver to ketones from body fat.

Ketogenic diet is thought to contribute to GABA increase and glutamate decrease.¹¹⁸
Ketogenic diet has been tested in epilepsy patients with good success. In diabetes, ketogenic diet is just required, because the insulin level is very much verse.¹¹⁹ ADHD sufferers with comorbid epilepsy are reported to experience benefits in hyperactivity, attention, and cognitive abilities in addition to improvement in epileptic seizures with ketogenic diet.¹²⁰ Although the author discusses nutritional issues in ADHD intensively, he does not name any benefits in ADHD without comorbid epilepsy.

Both gluten-free and ketogenic diets can affect the gut microbiome.⁸³
One metastudy discussed ketogenic diets as a potential treatment for type II bipolar disorder.¹²¹

In relation to ADHD, ketogenic nutrition has hardly been researched. In principle, the elimination of sugar associated with a ketogenic diet could be beneficial for sufferers with sugar intolerance. One study in rats found that ketogenic diets reversibly decreased the animals’ activity levels. Anxiety, on the other hand, was not reduced.¹²² Another study in dogs also found improvements in individual ADHD-related behaviors with a ketogenic diet.¹²³
In one individual case known to us, a consistent ketogenic diet did not produce any relevant improvements in ADHD symptoms.

1.3.2. Mediterranean diet¶

A Mediterranean diet in early pregnancy was associated with reduced mental health problems in children in one study.¹²⁴

A Mediterranean diet in children with ADHD was reported to have slightly improved impulsivity in one study.¹²⁵

1.3.3. Exorphins (no evidence verifiable)¶

An ADHD sufferer reported success on an exorphin-free diet.
Exorphins are atypical natural opiates found in food. They differ from endorphins by a different chemical composition.

Exorphins are for example:¹²⁶

• The casomorphins in bovine and ovine milk
• Β-Casomorphine in human breast milk
  • Whether β-casomorphin reaches the infant’s brain is open
  • Β-Casomorphine injected into the brain of young rats reduces opiate-like pain sensitivity¹²⁷
• Opiopeptides in wheat gluten
• Dermorphins (µ-receptor selective)¹²⁸
• Deltorphins (δ-receptor selective)¹²⁹

Opiate receptors in both humans and rodents are most densely located in the¹³⁰

• Posterior horn of the spinal cord
• Medial thalamus
• Brainstem
• Limbic system

In contrast, cannaboid receptors are found primarily in¹³¹

• Basal Ganglia
• Hippocampus
• Cerebellum
• Neocortex

Opiates

• Reduce pain sensitivity by inhibiting the firing rate of the neurons responsible for pain perception¹³²
• Inhibit the release of the neurotransmitters¹³²
  • Adrenalin
  • Dopamine
  • Acetylcholine
  • Substance P

1.3.4. Sweetener¶

• Aspartame

Aspartame is suspected of inhibiting the release of dopamine, norepinephrine, and serotonin, which (especially in ADHD) could lead to negative psychological consequences.¹³³
Aspartame is also marketed as the “natural” sweetener AminoSweet.

1.3.5. Trans fats (no evidence verifiable)¶

Trans fatty acids are formed, among other things, during the chemical hardening of fats. They are found in particular in hardened fats (e.g. margarine) and in foods containing hardened fats (e.g. ice cream, chocolate coating).

According to Dr. Bod DeMario, trans fats (such as palm oil), which are commonly used to prepare fast food because they are inexpensive, are thought to cause DHA deficiency.
The casein (casein) found in cow’s milk is also thought to reduce DHA.
In ADHD, excessive trans fat levels are detectable in the blood.

This statement could not be verified on this side so far. In any case, no studies by DeMaria on trans fats can be found on PubMed. The only study on trans fats in ADHD that can be found at all at PubMed¹³⁴ is also not even available as an abstract.
An American forum thread also came to no meaningful conclusion on this hypothesis.¹³⁵

1.4. Food (supplement) without influence on ADHD¶

1.4.1. Phosphate incompatibility (refuted)¶

The thesis of phosphate intolerance has been disproved.¹³⁶

Marcus³⁷ has justified this in detail:

• The legally permissible phosphate supplements in food comprise only 3% of the total phosphorus intake. Most phosphate is found in natural form in foods.
• Reduced dietary phosphate intake is compensated by the body through increased renal tubular reabsorption, so that the blood phosphate level is not reduced. Only the increase in the afternoon serum phosphate value is lower, but the fasting serum phosphate value remains unchanged.
• If phosphate were to trigger ADHD symptoms, an increased phosphate intake should be able to cause ADHD symptoms. However, corresponding tests could not confirm this.¹³⁷
• The diet that was promoted at the time as low in phosphates actually showed hardly any reduction in phosphate levels compared with a normal diet.

The effect of the low-phosphate diet could be based on its proximity to the oligoantigenic diet, which is still discussed today.

One affected person reports:

Note: Sugar is a possible “allergen” according to the oligoantigenic diet. The description covers for the individual case of sugar intolerance.

It is unlikely that children (and especially ADHD sufferers) will be able to seriously adhere to the requirements described when following a diet.

1.4.2. Salicylates (fine gold; refuted)¶

American Feingold postulated in the 1970s that salicylates and dyes can trigger ADHD
The theory regarding salicylates is considered outdated.
Feingold named several types of fruit and tomatoes as foods containing salicylates.¹³⁸
Many elimination diets cite different fruits and tomatoes as symptom triggers.
It would be interesting to know if there is any work that has studied the effect of salicylates on healthy people.
For dyes, see above.

2. Other nutrition-specific treatment approaches for ADHD¶

2.1. Desensitization of food intolerances¶

Although food intolerance is not an allergy, a double-blind placebo-controlled study by Egger, who has extensively researched elimination diets for ADHD presented here, successfully demonstrated desensitization to identified food intolerances. 16 of 20 participants developed tolerance, compared to 4 of 20 from the placebo control group.¹³⁹

2.2. Probiotic treatment can influence behavior¶

In an experiment in rats, probiotic treatment showed a reduction in depression symptoms. This was associated with changes in proinflammatory cytokines that moderate inflammation.¹⁴⁰ Further, probiotic treatment decreased transcription of CRH1, CRH2, and mineralocorticoid receptors in the hippocampus, while a high-fat diet increased them.

A single study found that of 75 children who received a probiotic (Lactobacillus rhamnosus GG, ATCC 53103) from 0 to 6 months of age, none developed ADHD or ASD by 13 years of age, while 17% in the placebo group received an ICD 10 diagnosis of ADHD or ASD.¹⁴¹

A metastudy found an effect of probiotic treatment on ADHD in only one of 7 studies. This study found a reduced risk of ADHD in children due to probiotic treatment of mothers during pregnancy and breastfeeding.¹⁴²

2.3. Increased intestinal permeability in ADHD¶

A study of 40 ADHD sufferers and 41 nonafflicted found elevated zonulin levels in the ADHD sufferers, which at the same time correlated with hyperactivity,¹⁴³ so there may be a higher association with ADHD-HI than with ADHD-I.

Zonulin is a 47 KD protein that regulates tight junctions in the intestinal wall. The intestinal mucosa secretes zonulin in response to specific stimuli. Zonulin binds to specific receptors on intestinal epithelial cells, which controls the opening of interepithelial channels by contraction of cytoskeletal proteins. Analysis of serum zonulin levels is simple and provides a reliable picture of intestinal permeability and indicates chronic inflammatory bowel diseases, such as;¹⁴⁴

• Celiac disease
• Diabetes mellitus
• Other autoimmune diseases
• Disturbed intestinal flora e.g. after antibiotic therapy

3. Further literature¶

Further literature on the subject of nutrition and ADHD can be found at

• www.adhs-deutschland.de
• ADHD-HI and diets. Dietary interventions as an appropriate treatment option for ADHD-HI?
• Romanos, Buske-Kirschbaum, Fölster-Holst (2011): Itches and scratches - is there a link between eczema, ADHD, sleep disruption and food hypersensitivity? Allergy 2011; 66: 1407-1409.