The potential of food colors approved by the Food and Drug Administration (FDA) to promote attention-deficit/hyperactivity disorder (ADHD) symptoms is not supported by the literature, says a new meta-analysis.
Results published in the Journal of the American Academy of Child & Adolescent Psychiatry indicate that food colors may promote ADHD symptoms, but when the data is limited to FDA-approved colors, this link is no longer reliable.
The study, by scientists from the Oregon Health and Science University and the International Life Sciences Institute (ILSI), was focused on data from randomized controlled trials, “because these provideprima faciaevaluation of causality”, explained the researchers.
However, the researchers note that the evidence base in the US is very limited, with “a complete absence of modern studies of this topic in the United States since the early 1990s”.
“The literature remains limited by lack of validation of blinding in many studies, and wide variation in methodology which would be best addressed by a pooled analysis of individual data across studies—not possible with the old literature.
“In short, despite 35 years of research and evidence of an effect of food colors on objective measures of attention, the database that would confirm this possibility and generalize it for contemporary use is woefully out of date with regard to policy or clinical decisions in the United States.”
Colors, kids and controversy
Controversy over the safety of artificial food colors has been raging for years, but reached a new frenzy in 2007 following the publication of a highly controversial study conducted by the University of Southampton in the UK suggesting a link between six food dyes – the ‘Southampton Six’ – and hyperactivity in children.
While EFSA concluded that the results could not be used as a basis for altering the acceptable daily intakes of the colors in question, the European Parliament baffled many observers by insisting that products featuring the colors should nevertheless include warning labels noting that they “may have an effect on activity and attention in children”.
However, the US FDA Food Advisory Committee has voted against recommending European-style warning labels on products containing artificial food colors in the US.
Given the divergent policy in the US and Europe, the researchers performed a meta-analysis of diet and food colors in ADHD and its symptoms.
The data revealed that information from parents indicate an effect of food colors on ADHD, but this was found to be a non-reliable link when information from teachers was used, or when the researchers limited their analysis to FDA-approved food colors.
There was an indication from ‘high-quality studies’ that color additives did yield a reliable effect relating to ADHD.
“Although as many as 8% may have symptoms related to food colors, the source of most of this dietary response remains unclear,” explained the researchers. “We thus conclude that dietary effects on and treatments of ADHD, including food additives and colors, deserve renewed investigation.”
Source: Journal of the American Academy of Child & Adolescent Psychiatry
Volume 51, Issue 1, Pages 86-97.e8
“Meta-Analysis of Attention-Deficit/Hyperactivity Disorder or Attention-Deficit/Hyperactivity Disorder Symptoms, Restriction Diet, and Synthetic Food Color Additives”
Authors: J.T. Nigg, K. Lewis, T. Edinger, M. Falk