A while back, I had a conversation with a middle school teacher who was telling me about a student who had attention-deficit hyperactivity disorder (ADHD). The teacher had noticed this student was eating unhealthy foods containing loads of added sugars and decided to pitch a new diet approach to the student. To everyone’s (delightful) surprise, after the kid tried the diet for a few weeks, his ADHD symptoms improved so dramatically that he stopped needing his ADHD meds.

So naturally, I got really interested with this story and decided to do some research on ADHD and diet, because to be honest I hadn’t explored this particular issue before.

Here’s a quick summary of all the digging I did.

What is ADHD?

Children suffering from ADHD have symptoms of hyperactivity, inattention and impulsiveness which are not age-appropriate and are usually persistent, disruptive and pervasive. It’s very important to correctly diagnose and treat ADHD and not assume that children will simply ‘grow out of it’ because the symptoms can negatively affect school performance, interpersonal relationships, family conflicts and may lead to serious issues like delinquency, substance abuse, depression and even suicide. Untreated ADHD increases the risk of developing other mental disorders. Children diagnosed with ADHD are often treated with a multimodal approach of medication combined with with psychosocial interventions and parental training. The prevalence of ADHD in children worldwide and in the UK is 5%. Although commonly associated with children, ADHD can still affect adolescents and adults!

What causes ADHD?

Both environmental and genetic factors are thought to contribute to the development of ADHD. Several non-dietary environmental factors can increase the risk of developing ADHD in children such as maternal smoking or stress during pregnancy, prematurity, low birth weight or exposure to environmental pollutants such as certain pesticides, industrial chemicals and lead. Then there are the dietary factors which may lead to developing ADHD. Here’s the bad news: there is no strong, consistent evidence about dietary factors that can be used to treat ADHD symptoms, and so far there are no guidelines in the UK for any dietary interventions. The good news is we have several clues.

Sugars

I initially started my search for articles regarding sugar intake and ADHD with exactly those terms. I was disappointed because I’ve found little evidence that increased sugar intake in children worsens their ADHD symptoms (I expected a strong correlation at the very least, based on the school teacher’s claims). Surprisingly, I’ve found a review article in the Pediatrics journal that argues how parents and physicians very strongly perceive sugar intake to be linked to hyperactivity in children with ADHD, while little scientific research (controlled studies) on that matter actually supports this. There are several theories on this topic such as: worse ADHD symptoms as a response to reactive hypoglycaemia after a high-sugar meal, increased aggression correlated to daily sugar intake, or an over-activation of brain functions following a sugar load.  There is some research about worse performance on memory tests after higher glycaemic load breakfast. However, research still cannot conclude a strong correlation of sugar intake on ADHD symptoms. Then again, absence of evidence is not necessarily evidence of absence. We can need more research in this area.

The Feingold diet

In the 1970s, Dr Feingold hypothesis that ADHD in children is the result of an allergic reaction to natural food salicylates or artificial food additives*. He advised to eliminate all foods containing those ingredients from the child’s diet to improve the ADHD symptoms. Since then, many studies have been conducted on the Feingold diet’s effect on ADHD. Several studies (with varying methodological flaws and differences) found different results: some found that children exposed to the additives or salicylates had worsened ADHD symptoms, while others found no notable differences. Recent meta-analyses of studies on this topic, which are not of excellent quality, showed that artificial food colourings have a small but significant negative effect on some, but not all, children with ADHD. The NICE guidelines in the UK do not recommend the elimination of additives.

*natural salicylates are found in luncheon meats, hot dogs, sausages, apples and grapes. Artificial food additives are commonly found in processed foods, make sure to check the ingredients list.

The elimination diet

This diet is similar in concept but more restrictive than the Feingold diet: it eliminates all foods that may cause sensitivities or allergies (which is a lot of foods, really). The meta-analysis of many studies that researched the effect of elimination diets on ADHD found that overall, there seems to be a beneficial ‘reliable and clinically meaningful’ effect on ADHD symptoms associated with children following elimination diets. A study found that a subgroup of children with ADHD improved after following an elimination diet, so it may be worth a shot to determine if the child’s ADHD is food-induced. It is important to mention that the elimination diet is overly restrictive, so adherence to it by both the child and the parents may become a problem. Parents who want to try it should work very closely with a trained dietitian, however NICE also does not recommend following this dietary approach because of the uncertainty of its long-term benefits.

Polyunsaturated fatty acids and minerals supplements

There are many nutrients involved in cognitive and neurological functions, including iron, zinc and long-chain polyunsaturated fatty acids (LC-PUFAs), so they are also thought to influence ADHD symptoms. Some research found that children who have ADHD tend to have low levels of circulating LC-PUFAs. In response, several studies tested the effects of LC-PUFA supplements on ADHD symptoms, but a Cochrane review found there is little evidence that such supplements have any benefits, with more research needed. Similarly, research has shown that children with ADHD were often found to have lower serum ferritin levels (a marker of iron status) than children without ADHD. Iron supplementation was not found to significantly improve ADHD symptoms. Zinc has a similar story in that studies did find a correlation between low zinc status and symptom severity of ADHD, but there is not enough research to whether any of these are causal factors or that supplements should be added as treatments for ADHD symptoms.

Mediterranean Diet

Finally, a case-control study was published very recently that examined the diets of healthy children and adolescents versus the diets of those diagnosed with ADHD. The findings showed that low adherence to the Mediterranean diet is associated with (really) high odds of being diagnosed with ADHD. Of course, this is an observational study and stronger research including clinical trials are needed, but this finding now sheds light on the possibility that it is not a single nutritional factor, but rather a holistic dietary approach that may be more helpful in improving ADHD symptoms or diagnosis.

Conclusion

Although several dietary factors can influence the symptoms of ADHD, there is no clear causation for any particular element yet. Nutrition does have an important role to play, but we have yet to crack this code. Parents or caregivers can start by consulting with their child’s dietitian to try different dietary approaches, starting with monitoring potential foods that influencing the ADHD symptoms for the child and eliminating them. There is no clear-cut approach that would suit all children’s needs, and changing up the child’s diet is an option, since any modification will likely involve replacing healthy foods with less healthy ones, so discussing different options with a dietitian is a good place to start. Please do not start supplements or dietary modifications before first discussing it with your dietitian who can guide you better.

Laura Jabri, MSc 

Laura has a masters in Clinical and Public Health Nutrition from University College London and a bachelors degree from the American University of Beirut. Her interests include nutrition education, obesity prevention, maternal and child nutrition, undernutrition in developing countries and food sustainability solutions.  Tweet her @laurajabri

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