My son’s 3rd-grade teacher assigned her students a research question for homework to report whether the artificial food coloring red dye #40 causes attention deficit hyperactivity disorder (ADHD)? Although I don’t know if the teacher had a specific agenda in mind, the vast majority of my son’s peers concluded (largely on the basis of internet searches) that red dye does cause ADHD (among other things). I remain skeptical and wonder both about your thoughts on this topic as well as how to respectfully raise the level of skepticism among parents, 3rd graders, and teachers to internet “information”.
I love this question and your desire to raise the bar for what counts as evidence, whether it be for a critical healthcare decision or a 3rd-grade science report.
Regarding whether red dye #40 causes ADHD or related symptoms, I first did a quick Google search out of curiosity. Notably, the way I did my search significantly influenced the results. When I searched “red dye#40 linked to ADHD” I get mostly positive results. When I searched “Do food dyes cause ADHD?” I get mixed responses with about 50% of sites on the first page reporting no linkage. As a first lesson, a leading question, whether presented to 3rd graders or the internet, is likely to lead to a biased result.
I’m also not immune to bias. Before checking my sources, I wanted to believe that there was no link and that the internet headlines attributing a causal relationship were misrepresenting chance associations. What I found however was much more interesting and taught me quite a bit about food additives and ADHD.
The first important concept is that ADHD is a spectrum disorder. This means that the diagnosis is based on crossing a certain threshold of a continuous symptom (attention and hyperactivity). High blood pressure is another spectrum disorder. This is in contrast to a categorical disorder like tuberculosis or cancer where you either have it or you don’t. Importantly, for spectrum disorders small changes in a symptom for people near the threshold can make the difference between meeting diagnostic criteria or being “normal”.
The idea that artificial food dyes could cause behavioral problems in children dates back to the 1920s but became popular in the 1970s with the publication of the bestselling book Why You Child is Hyperactive by Dr. Benjamin Feingold. This book included Dr. Feingold’s observational data as well as dietary recommendations. (see Arnold et al, for a great overview of the history and the science through 2012)
Although a book like this might trigger your BS detector, studies over the ensuing decades largely validated Dr. Feingold’s observations. This includes both animal studies (to look at potential mechanisms), epidemiologic studies (to look for real-world associations), and experimental studies (to examine causal relationships). As food dyes are fairly easy to mask (they are tasteless), it was not hard for researchers to blind participants and parents as to whether the food and beverages they were given had dye.
To summarize the most recent research, the majority of experimental studies find that red dye #40 (at allowable/safe levels per the FDA) is linked to hyperactive behavior and changes in sleep, but only in about 10% of children. Notably, this effect was seen equally in children with and without a diagnosis of ADHD. As ADHD is a spectrum disorder, this change in behavior may lead to a diagnosis of children who are near the cut-off for attention/hyperactivity symptoms. Animal studies also suggest some plausible mechanisms, including changes in neurons, endocrine function, and absorption of other nutrients.
So what do we do with this information? If you live in some European countries you don’t need to worry about it because these (and other) chemicals are either banned from human consumption or prominently labeled on the packaging. If you live in the US, it is up to you to read the ingredient list and decide what is safe for you and your children to eat.
My advice would be:
Pay attention to your child’s behavior and if you notice a correlation with certain foods consider eliminating them from the diet and see if the behavior improves. As artificial food colorings seem to affect 10% of children there is a fair chance that these may not impact your child, or might be OK for an occasional treat.
If you are concerned about your or your children’s health pay attention to what you are putting into your body. There is a growing amount of evidence that not just artificial food coloring, but sugar-sweetened beverages and other highly processed foods can have adverse effects on multiple aspects of health from ADHD, to weight to risk for chronic conditions like cancer and dementia. I’m sure there will be more blogs and questions about this in the future.