Dietary Interventions & ADHD

 

Can certain foods and supplements have a positive influence on ADHD symptoms? 

Below is a review of the research around dietary interventions and ADHD. A general overview of healthy eating can be found here.

 

Restrictive elimination diets & ADHD

The potential to reduce ADHD symptoms by following an elimination diet is based on the hypothesis provided by Feingold (1975). Feingold proposes that some children are sensitive to certain dietary substances and that reaction to these substances may contribute to ADHD symptoms.

The limited research into this hypothesis so far has shown restrictive elimination diets may result in marginally significant behaviour changes. The accuracy of these study results however is questionable. This is due to low reported response rates as a significant number of participants dropped out of each of the studies (between 41-47%).

Before deciding to trial a restrictive elimination diet it may be helpful to consider whether the significant effort, resources and time required to trial such a diet, as well restrict any foods found to contribute to negative behaviour changes in the long-term, is worth the marginally significant behaviour changes that may or may not result. Especially if maintaining the diet will add to parental stress and/or compliance will be challenging or affect social inclusion. It is also worth considering that the long-term outcomes of restrictive elimination diets have not been evaluated.

If you do decide to trial a restrictive elimination diet, Barkley (2015) provides the following information and considerations:

• restrictive elimination diets trialled with children with ADHD typically eliminate diary products, gluten, citrus fruits, corn and products that contain corn, and all processed foods (however, most children are not sensitive to all, if any, of these foods)
• trial of a restrictive elimination diet should occur with support from a physician or dietician to ensure the child maintains an adequate nutrition intake during the process. To do so, substitute foods are often required  
• at the commencement of the diet, all restricted foods are eliminated for a couple of weeks. Then one-by-one they are added back into the diet (allowing a day for each). This enables the parent to determine which food (if any) evokes a significant behaviour change
• if no significant behaviour change occurs the food should remain in the child’s diet
• if a negative behaviour change does occur the food should be eliminated indefinitely
• if the results are ambiguous, the parent can repeat the test by offering the food again the following week
• if a child sticks to the restrictive elimination diet at home but eats restricted foods at any other time (i.e. school, daycare, a friends house) the results will be inconclusive
• following the trial period, only foods that have been found to worsen behaviour should continue to be eliminated to reduce the risk of nutritional deficits developing.

 

Restriction of artificial food colours & preservatives

The recommendation to restrict artificial food colours and preservatives is not limited to children with ADHD, as two studies have shown these products tend to cause significantly worse behaviour in all children who consume them (Barkley, 2015). Therefore elimination or reduction in intake of artificial food colours and preservatives is advised where possible. 

 

Sugar restriction

Many people believe sugar ingestion leads to problematic behaviour in children with ADHD. However according to Russell Barkley (2015), the research does not support this claim. For example, a well controlled trial conducted by Wolraich et al. (1994) found sugar had no effect on the cognitive or behavioural function of children with ADHD.

Although sugar reduction is not recommended as a treatment strategy for ADHD, minimisation of added sugar intake is recommended for the maintenance of overall health. For example, the World Health Organisation Guidelines (2015) recommend individuals reduce their daily intake of added sugar to less than 10% of their total energy intake. They also state a further reduction to below 5% or roughly 25 grams (6 teaspoons) per day would provide additional health benefits.

 

Essential fatty acids & ADHD

Omega-3 and omega-6 are considered essential fatty acids because we cannot synthesise them and therefore they must be consumed. They have overall health benefits as they are necessary for neuronal membrane structure, fluidity, and function. They also constitute the substrate for prostaglandin and other eicosanoid production.

According to Russell Barkley (2015):

• Essential fatty acid supplementation may make a small but significant different in ADHD symptoms (although the research is not conclusive).
  
  • It appears that children who have not responded to evidence based treatments (i.e. medication and behaviour therapy) may benefit from supplementation. However, children who have an excellent response to traditional medication may not.
  • Barkley adds it is conceivable that essential fatty acid supplementation may reduce traditional medication maintenance dosage (but states there is no data to currently support this).
• Essential fatty acid supplementation meets the SECS guideline (meaning the treatment is safe, easy, cheap, and sensible) and does not need much evidence to warrant trialling (in comparison to a product that fits the RUDE criteria – risky, unrealistic, difficult and expensive).
• Supplementation is probably not necessary if a child or adult eats three serves of oily wild ocean fish weekly.
• Between 1-2 grams is considered to be effective and safe, as long as the product has been refined to eliminate mercury.
• It can take 3 months before any beneficial result are obtained.

 

Vitamin supplementation

Currently no controlled trials examining children or adults diagnosed with ADHD and the effects of vitamin supplementation have been undertaken. One placebo controlled trial in a non-diagnosed classroom found an improvement in non-verbal cognitive skills, and another similar trial, improved concentration and reduced fidgeting (although these improvements may have been limited to children with poor diets) (Barkley, 2015). However, a longer placebo controlled trial did not find vitamin supplementation resulted in any advantage when it came to reasoning tasks.

For this reason multivitamins are not considered a valid stand-alone ADHD treatment. In terms of general health and wellbeing, they may however be advantageous for adult or children with inadequate micronutrient intake due to poor food choices or stimulant medication induced appetite suppression.

Please note: Caution should be taken in the presence of rare genetic disorders.

 

Iron supplementation

According to two small pilot studies, low iron levels may exacerbate ADHD symptoms as supplementation appears to significantly reduces symptoms (Barkley, 2015). However, not all children or adults with ADHD have low iron levels. Iron supplementation is therefore only recommended for individuals with diagnosed iron deficiency. This is due to the risk of hemochrombtosis (excess iron) which can poison organs and cause pain and fatigue, as well as lead to conditions such as cardiomyopathy (disease of the heart muscle), pancreatic damage and cirrhosis of the liver.

 

Zinc & magnesium supplementation

The research into zinc supplementation as a treatment for ADHD is thus far inconclusive. As zinc is involved in the regulation of dopamine production and is necessary for melatonin production and fatty acid absorption, zinc supplementation may be recommended for individuals with zinc deficiency. However as zinc can interfere with the absorption or iron and copper, zinc supplementation when levels are adequate is not considered to be a valid ADHD treatment.

The research into magnesium supplementation as a treatment for ADHD is also inconclusive. Whilst a few studies indicate magnesium supplementation can significantly reduce ADHD symptoms when an individual is magnesium deficient, supplementation when magnesium levels are within the normal range can worsen ADHD symptoms. Magnesium supplementation is therefore only recommended for individuals with diagnosed magnesium deficiency.

 

Carnitine supplementation

Carnitine is considered to be a semi-essential micronutrient (as many individuals do not make enough of their own). It plays a significant part in energy production, lipid transport into the mitochondria and poly-unsaturated fatty acid elongation. It also has documented cardiac benefits.

According to Barkley (2015) there is minimal research to support carnitine supplementation as a stand-alone ADHD treatment. However, as there is some research that indicates it may benefit children with ADHD inattentive subtype (and it meets the SECS criteria), Barkley (2015) proposes it may be worth trialling on these children only. Supplementation needs to occur for 4 months to effectively evaluate its effects.

Please note: Carnitine supplementation is not recommended for ADHD combined subtype or ADHD hyperactive-impulsive subtype.

 

 

 

References

Barkley, R.A. (2015). Attention Deficit Hyperactivity Disorder: A Handbook for Diagnosis and Treatment, 4th ed. New York: Guilford Publications.

Feingold, B. F. (1975). Why your child is hyperactive. New York: Random House.

Wolraich, M. L., Lindgren, S. D., Stumbo, P. J., Stegink, L. D., Appelbaum, M. I., & Kiritsy, M. C. (1994). Effects of diets high in sucrose or aspartame on the behaviour and cognitive performance of children. Journal of the American Medical Association, 274, 1617-1621.

World Health Organisation. (2015) Healthy Diet – Fact Sheet. www.who.int/mediacentre/factsheets/fs394/en/