There's no evidence that the behavioral disorder ADHD is caused by diet.
However, research suggests that for some people, dietary changes can improve symptoms.
In fact, a substantial amount of research has examined how nutrition affects ADHD.
This article is an overview of these findings, discussing the foods, diets and supplements involved.
The exact cause of ADHD is unclear, but research shows that genetics play a major role. Other factors, such as environmental toxicity and poor nutrition during infancy, have also been implicated (5, 6, 7, 8).
Bottom Line: ADHD is a complicated behavioral disorder, and common treatments include therapy and medication. Dietary changes may also be useful.
The science behind food's effects on behavior is still quite new and controversial. However, everyone can agree that certain foods do affect behavior.
Nutritional deficiencies can also affect behavior. One study concluded that taking a supplement of essential fatty acids, vitamins and minerals led to a significant reduction in antisocial behavior, compared to a placebo (24).
Since foods and supplements have been shown to influence behavior, it seems plausible that they could also affect ADHD symptoms, which are largely behavioral.
For this reason, a good amount of nutrition research has looked into the effects of foods and supplements on ADHD.
Mostly, two types of studies have been performed:
- Supplement studies: Supplementing with one or several nutrients.
- Elimination studies: Eliminating one or several ingredients from the diet.
Bottom Line: Studies show that certain foods and supplements do affect behavior. For these reasons, quite a few studies have looked into how nutrition affects ADHD symptoms, which are mostly behavioral.
This caused researchers to speculate that supplements might help improve symptoms.
Nutrition studies have looked into the effects of several supplements on ADHD symptoms, including amino acids, vitamins, minerals and omega-3 fatty acids.
Amino Acid SupplementsEvery cell in your body needs amino acids to function. Among other things, amino acids are used to make neurotransmitters, or signaling molecules in the brain.
In particular, the amino acids phenylalanine, tyrosine and tryptophan are used to make the neurotransmitters dopamine, serotonin and norepinephrine.
For this reason, a few trials have examined how amino acid supplements affect ADHD symptoms in children.
Bottom Line: Amino acid supplements for ADHD show some promise, but more studies need to be done. For now, the results are mixed.
Vitamin and Mineral SupplementsIron and zinc deficiencies can cause cognitive impairment in all children, whether or not they have ADHD (36, 37, 38).
Nevertheless, a 2014 trial of a multivitamin and mineral supplement did find an effect. The adults taking the supplement showed a convincing improvement on ADHD rating scales after 8 weeks, compared to the placebo group (49, 50).
Bottom Line: The results from vitamin and mineral supplement studies have been mixed, but several show promise.
Omega-3 Fatty Acid SupplementsOmega-3 fatty acids play important roles in the brain.
What's more, the lower their omega-3 levels, the more learning and behavioral problems the ADHD children seem to have (53).
Bottom Line: Numerous trials have found that omega-3 supplements can bring about modest improvements in ADHD symptoms.
Studies have examined the effects of eliminating many ingredients, including food additives, preservatives, sweeteners and allergenic foods.
Eliminating Salicylates and Food AdditivesBy accident, an allergist named Dr. Feingold discovered that food could affect behavior.
In the 1970s, he prescribed a diet to his patients that eliminated certain ingredients that produced a reaction for them.
The diet was free of salicylates, which are compounds found in many foods, medications and food additives.
While on the diet, some of Feingold's patients noted an improvement in their behavioral problems.
Soon after, Feingold started recruiting children diagnosed with hyperactivity for dietary experiments. He claimed that 30–50% of them improved on the diet (67).
Although reviews concluded the Feingold diet was not an effective intervention for hyperactivity, it stimulated further research into the effects of food and additive elimination on ADHD (69, 70, 71).
Bottom Line: The Feingold diet pioneered elimination diet research for ADHD. It improved symptoms in children with ADHD, although recent evidence is mixed.
Eliminating Artificial Colorants and PreservativesAfter the Feingold diet was no longer considered effective, researchers narrowed their focus to look at artificial food colors (AFCs) and preservatives.
One study followed 800 children suspected of hyperactivity. 75% of them improved while on an AFC-free diet, but relapsed once given AFCs again (74).
Another study found that hyperactivity was increased when 1,873 children consumed AFCs and sodium benzoate, a preservative (75).
Nonetheless, the FDA requires certain AFCs to be listed on food packages. The EU, on the other hand, requires foods containing AFCs to have a label warning of adverse effects to children's attention and behavior (80, 81, 82, 83).
Bottom Line: AFCs may affect behavior in children, although some say the evidence is not strong enough. However, the FDA and the EU require food labels to list additives.
Eliminating Sugar and Artificial SweetenersSoft drinks have been linked to increased hyperactivity, and low blood sugar is also common in those with ADHD (84, 85).
Theoretically, it's more likely that sugar causes inattention, rather than hyperactivity, as blood sugar imbalances can cause attention levels to drop.
Bottom Line: Sugar and artificial sweeteners have not been shown to directly affect ADHD. However, they may have indirect effects.
The Few Foods Elimination DietThe Few Foods Elimination Diet is a method that tests how people with ADHD respond to foods. Here's how it works:
- Elimination: Follow a very restricted diet of low-allergen foods that are unlikely to cause adverse effects. If symptoms get better, enter the next phase.
- Reintroduction: Foods suspected of causing adverse effects are reintroduced every 3–7 days. If symptoms return, the food is identified as "sensitizing."
- Treatment: A personal dietary protocol is prescribed. It avoids sensitizing foods as much as possible, in order to minimize symptoms.
The reason why this diet works for some children and not others is unknown.
Bottom Line: The Few Foods Elimination Diet is a diagnostic tool to rule out problems with food. All studies have found a favorable effect in a subgroup of children, usually more than half.
Research on the effects of food on ADHD symptoms is far from conclusive.
Yet the studies mentioned here suggest that diet can have powerful effects on behavior.