Food Dyes and ADHD
Synthetic additives and processed food warrant caution, but not alarm.
Posted February 11, 2020 | Reviewed by Davia Sills
An enduring controversy in the ADHD world is the role of diet and, in particular, synthetic food dyes. This issue has come to the forefront again recently because the State of California is reviewing the data and considering requiring labels on foods like Great Britain did previously. (Full disclosure, I was asked to consult with the California review; you can see the full contents of the two-day scientific review symposium with outside experts here.)
The idea that food and features of the modern diet are somehow related to behavior problems in children dates at least to the early 20th century. However, the specific proposal of synthetic food dyes (and other features of food) relating to ADHD gained prominence through the work of Benjamin Feingold in the 1970s.
Professional opinion on this issue has tended toward skepticism due to limited confirmation in numerous small studies. In 2011, the FDA reviewed the evidence, and although they admitted that some children are sensitive to food dyes and that this may exacerbate ADHD symptoms, they opted not to take any action. In contrast, beginning in 2010, European Union countries have added a warning label to foods containing synthetic dyes indicating they may increase inattention or hyperactivity.
Colleagues and I conducted a thorough review of this literature in 2012, and little has changed since then. (One more study was published after that, but its results were not presented clearly enough to allow us to include in a re-analysis.) We examined the literature in numerous ways—parsing out studies in relation to whether or not they were restricted to FDA-approved dyes (many done in Europe or Australia were not), the quality of the studies, the availability of objective measures, and whether or not the sample of children was pre-selected to be hyperactive (versus a general population sample of kids) or to have food allergies.
Overall, we confirmed that food dyes increase ADHD symptoms somewhat. We pooled the results of all available double-blind, randomized trials—the gold standard for causal testing in medicine. We considered parent report, teacher report, and objective computerized tests of attention at the outcome measure. The effects were similar across these three sources. They were also similar in general population samples or in children with ADHD.
This suggests that to the extent that food dyes affect ADHD symptoms, this is a public health concern that is not ADHD-specific. While the overall effects of food dyes on ADHD symptoms seem clear enough, there were numerous caveats. For example, the effects are small. A small effect may still be important for public health, but would not be enough clinically to account for most ADHD.
It would also not be enough to typically treat diet adjustment as a substitute for standard care. Instead, it might be a supplement to standard care that will help some children. But I have to note some additional caveats.
I noted that the effects were small in size. They were even smaller when we consider “publication bias.” Publication bias is the tendency not to publish small studies that don’t give a “significant” finding; certain statistical methods try to adjust for this effect.
On the other hand, it seemed that some children had big effects. In other words, there seem to be some children who are particularly sensitive. Therefore, some children may benefit from the avoidance of synthetic food dyes.
Studies are small and varied. However, the highest quality studies had the biggest effects.
The parent report result could be due to publication bias (it would take very few unpublished negative studies to reduce the effect to indistinguishable from zero).
The important effect on objective tests of attention was compelling—not explainable by publication bias or rater bias, and restricted to FDA colors in the U.S. the effect held. However, that result depended on a small number of total children studies (less than 150 overall across all studies). Further, each of the handful of studies can be criticized.
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There are few studies in the United States not restricted to FDA colors—so we can’t be sure the effect is robust when restricting to FDA-approved colors (even though we have little reason to think it would be different).
A key issue
We identified 10 studies done in the United States. The last one was published in 1981—over 35 years ago. Studies were subsequently done in Australia and Great Britain in the 1990s up until 2007 (and one in Hong Kong in 2016 that was inconclusive in my view). Yet diets and food content have continued to evolve.
In fact, the total amount of synthetic additives in children’s diets is much greater now than it was 35 years ago. Stevens and others, in a 2014 essay on Artificial Food Colors (AFCs), noted,
“The amount of AFCs the Food and Drug Administration has certified over the years has increased more than 5-fold since 1950 (12 mg/capita/day) to 2012 (68 mg/capita/day). In the past 38 years, there have been studies of adverse behavioral reactions such as hyperactivity in children to double-blind challenges with AFCs. Studies that used 50 mg or more of AFCs as the challenge showed a greater negative effect on more children than those which used less.”
There is a real possibility that these effects are larger than what the older, aggregated literature shows in everyday life. Thus, there is an urgent need for an updated, properly conducted study in the United States. The policy changes in the EU were based heavily on a population study in England. What about the U.S.? We don’t have a comparable American study.
What Do I Recommend?
The value judgment required by policymakers and parents is this: Do we feed our children products with uncertain safety data until they are definitely proven harmful? Or do we restrict products with uncertain safety data until they are proven safe?
The FDA has decided to allow dyes until harm is more definitely proven. The EU has decided to restrict their use until they are proven safe. My own view is that food dyes are not proven safe for children, and certainly may increase symptoms of inattention or hyperactivity. For some children, this may be one too many challenges to their nervous system and contribute to ADHD symptoms.
My own children will not be given food with synthetic dyes if I can help it. While acknowledging that the data are weak, my bias is toward child safety and avoiding needless risks that have little upside. Thus, given they have little value, I recommend parents avoid these food dyes if they can. The synthetic dyes have no nutritional value and are mainly used to make processed food more palatable. As I outlined in my book, Getting Ahead of ADHD (Chapter 3), a healthy diet with less processed food is a good idea in general for children, and worth the effort and expense if you can manage it. This is one part of that theme.
On the other hand, if you don’t suspect your child is sensitive to dyes, then you may decide that other priorities are higher. A parent cannot consider all possible aspects of potential risk for children, and we have to prioritize. Dyes are somewhere on the list, but for most parents, they may not be as important as, say, avoiding lead exposure or making sure your child gets enough exercise and a healthy diet overall.
Please note: Dr. Nigg cannot advise on individual cases for ethical, legal, and logistical reasons.
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