What is ADHD?
ADHD, or Attention Deficit Hyperactivity Disorder, is a neurodevelopmental disorder that affects both children and adults. Individuals with ADHD often display persistent patterns of inattention, hyperactivity, and impulsivity, which can significantly impact their daily functioning and development. This can lead to adverse effects on academic performance, vocational success, and social-emotional development. While the exact cause of ADHD is not fully understood, research suggests that it is rarely attributed to a single genetic or environmental risk factor. Instead, ADHD is believed to result from the combined effects of numerous genetic and environmental factors (1). Furthermore, there is growing evidence supporting a link between ADHD symptoms and specific food sensitivities, which will be further discussed below.
Food sensitivity and ADHD
One of the most well-known claims linking food sensitivity to ADHD was made by pediatric allergist Dr. Ben Feingold. He proposed that additives like artificial food colors (AFC), flavors, and preservatives (such as BHA, BHT and TBHQ), and food chemicals like salicylates, could be responsible for the increasing prevalence of behavior and learning problems in children (2). Dr. Feingold suggested that eliminating these substances from the diet could lead to improvements in symptoms.
While there aren’t any well-designed studies assessing the Feingold program as a whole, multiple studies have been conducted on different aspects of the diet. For instance, one study demonstrated an association between AFCs and hyperactivity (3), while another found that food additives such as artificial colors and preservatives increase hyperactivity in children under nine years of age, regardless of whether they have ADHD or not (4). A meta-analysis (6) emphasising randomised controlled trials concluded that a restricted diet improves ADHD symptoms. Specifically, parents reported that food additives tend to increase ADHD symptoms in their children.
Regarding salicylates, researchers in the 1980’s showed that there were more foods containing salicylates than previously thought (9), providing a possible explanation for the negative results of controlled studies of the Feingold diet which contained foods high in salicylates. Similarlly, an open trial of a low salicylate and low additive diet, showed that 80% of 516 children with behaviour problems improved significantly (10).
Conversely, several studies have refuted the link between food intolerance / AFCs and ADHD. However, many of these studies have been shown to be biased and fraught with methodological problems (8). Interestingly, while not in line with the scientific method, there have been tens of thousands of anecdotal reports from families about the success of eliminating certain foods from their child’s diet to improve behaviour.
While research shows that AFC may not be a major cause of ADHD in and of itself (remember, it is a multifaceted disorder), it does appear to contribute significantly to a subgroup of children with ADHD (the size of which is unknown), and may even be responsible for additively pushing a person over the diagnostic threshold (5). Two large studies also demonstrated behavioral sensitivity to AFCs and benzoate in children both with and without ADHD (7). Therefore, one could argue that artificial food colouring may be more of a public health issue than specifically an ADHD one.
The study of the link between artificial colours, flavours, and preservatives and ADHD is still a work in progress. “Diet” is a difficult area to research, with factors such as dose and exposure lengths, methodologies, and blinding quality making it hard to reach a scientific consensus. However, it should be noted that the current evidence is perhaps too considerable to completely dismiss. Based on this sentiment, Europe has led the way in removing many of these chemicals from products by asking manufacturers to voluntarily remove artificial food colourings from foods and beverages. The United Kingdom has also taken action by requesting that food manufacturers avoid these artificial additives in favour of natural food colourings and flavours.
Diagnosis of food intolerance
While some individuals, both children and adults, may exhibit ADHD-type symptoms in response to common food chemicals and additives, current research has not yet established these as the primary causes of ADHD. There are currently no blood tests or laboratory tests to determine who are diet responders, and individuals will vary in their tolerance and/or improvement to a group of suspect food chemicals. Thus, diagnosing hypersensitivities to these substances is a complex process that may require the guidance of a healthcare professional to ensure the diet analysis is conducted adequately and that proper nutritional balance is achieved.
Typically, an elimination diet is implemented, which involves removing all artificial flavors, preservatives, and other food chemicals associated with food intolerances (such as salicylates, amines, lactose, etc.). A comprehensive food and family history can help match the level of restriction to the severity of symptoms. These substances are then gradually reintroduced into the diet, allowing for the identification of specific foods that may trigger behavioral changes. It’s also important to note that treatment for ADHD often involves a combination of medication, therapy, and behavioral/dietary interventions to help manage symptoms and improve daily functioning.
Conclusion
Based on the above research, there is a clear link between an individual’s diet and their behaviour. Colours and preservatives can exaccerbate underlying behavioural tendencies in those sensitive to these chemicals, impacting their ability to focus, pay attention, and control impulses. It’s important to remember that while diet may be a factor, ADHD has many parts that need to be pieced together to solve the puzzle, thus food isn’t always the main driver of ADHD symptoms for an individual. If you suspect that you or someone you know may have ADHD, it is important to consult with a healthcare professional for a proper diagnosis.
References
(1) Faraone SV, Banaschewski T, Coghill D, Zheng Y, Biederman J, Bellgrove MA, et al. The World Federation of ADHD International Consensus Statement: 208 Evidence-based conclusions about the disorder. Neurosci Biobehav Rev. 2021 Sep;128:789-818. doi: 10.1016/j.neubiorev.2021.01.022. Epub 2021 Feb 4. PMID: 33549739; PMCID: PMC8328933.
(2) Feingold BF. Adverse reactions to food additives. Presented at: The American Medical Association Annual Meeting; June 24–28, 1973; Chicago, IL.
(3) Schab DW, Trinh NH. Do artificial food colors promote hyperactivity in children with hyperactive syndromes? A meta-analysis of double-blind placebo-controlled trials. J Dev Behav Pediatr. 2004 Dec;25(6):423-34. doi: 10.1097/00004703-200412000-00007. PMID: 15613992.
(4) McCann D, Barrett A, Cooper A, Crumpler D, Dalen L, Grimshaw K, Kitchin E, Lok K, Porteous L, Prince E, Sonuga-Barke E, Warner JO, Stevenson J. Food additives and hyperactive behaviour in 3-year-old and 8/9-year-old children in the community: a randomised, double-blinded, placebo-controlled trial. Lancet. 2007 Nov 3;370(9598):1560-7. doi: 10.1016/S0140-6736(07)61306-3. Erratum in: Lancet. 2007 Nov 3;370(9598):1542. PMID: 17825405.
(5) Arnold LE, Lofthouse N, Hurt E. Artificial food colors and attention-deficit/hyperactivity symptoms: conclusions to dye for. Neurotherapeutics. 2012 Jul;9(3):599-609. doi: 10.1007/s13311-012-0133-x. PMID: 22864801; PMCID: PMC3441937.
(6) Nigg JT, Lewis K, Edinger T, Falk M. Meta-analysis of attention-deficit/hyperactivity disorder or attention-deficit/hyperactivity disorder symptoms, restriction diet, and synthetic food color additives. J Am Acad Child Adolesc Psychiatry. 2012 Jan;51(1):86-97.e8. doi: 10.1016/j.jaac.2011.10.015. PMID: 22176942; PMCID: PMC4321798.
(7) Stevens LJ, Kuczek T, Burgess JR, Hurt E, Arnold LE. Dietary sensitivities and ADHD symptoms: thirty-five years of research. Clin Pediatr (Phila). 2011 Apr;50(4):279-93. doi: 10.1177/0009922810384728. Epub 2010 Dec 2. PMID: 21127082.
(8) Smith, M. (2008). History and Hyperactivity: the Feingold Diet. History & Policy. www.historyandpolicy.org/index.php/policy-papers/papers/history-and-hyperactivity-the-feingold-diet
(9) Swain AR, Dutton SP, Truswell AS. Salicylates in foods. J Am Diet Assoc 1985;85(8):950-60.
(10) Breakey J, Hill M, Reilly C, Connell H. A report on a trial of the low additive, low salicylate diet in the treatment of behaviour and learning problems in children. Aust J Nutr Diet 1991;48(3):89-94.
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