We are what we eat so they say. For ADHD the link between the foods we eat and the effect on the symptoms is unclear. To get some insight, we spoke to leading ADHD author and researcher Dr. Joel Nigg to find out what the current science says.
Disclaimer: the information contained on this website does not constitute medical advice. If you have concerns about your own health or the health of someone else, you should speak to your doctor.
Is there a link between ADHD and what we eat?
Yes, I think there is. We've had several studies now showing correlations with Omega 3 deficiency in the blood in those with ADHD. Some studies have also showed that extra Omega 3 supplements can benefit ADHD symptoms. That's pretty well established, even though the effect sizes are fairly modest. We know it's not going to be a cure for ADHD but it does seem to have some effect.
There's some ambiguity or weaker literature that suggest that some food additives, food dyes and preservatives affect ADHD symptoms. I think that evidence is clear, although it's unclear how many children with ADHD this affects or whether it's only food dyes or food dyes plus other factors that are affecting ADHD. With those ambiguities acknowledged, there seems to be some link between these ingredients and ADHD.
There's also a small amount of literature suggesting that food restriction or getting rid of allergenic foods benefits some children with ADHD.
Overall, I think there's quite a bit of evidence that there is an association with diet and ADHD symptoms; there are some specific dietary negatives and potential positives that can help with ADHD. I think it's an area we in the scientific community are going to want to watch closely and study more to find out what therapeutic opportunities there are in this field.
Are there any foods that should be avoided altogether?
I think there’s growing evidence to suggest that people should move in the direction of the anti-inflammatory diet - taking inflammatory foods and eating foods high in omega 3. I also think it would be helpful to reduce the intake of processed food, foods with a lot of additives, dyes and preservatives - focussing more on fresh foods.
Of course, these things are going to be better for overall health, not just for ADHD. For families who suspect that food is a factor to the severity of their child’s ADHD symptoms, it's not unreasonable to explore their diet in more detail.
Does sugar impact ADHD symptoms?
It's unclear. Certainly, there's plenty of circumstantial evidence from teachers and parents that, when kids eat junk food, their behavior worsens. I was talking to a teacher earlier this week who pointed out that, when they gave kids these giant heavily frosted cupcakes to the class for a birthday party, the kids’ behavior worsened significantly shortly afterwards. Whether it was the sugar or the food additives or something else, it's a common observation.
Except for the food dyes, it's very difficult to demonstrate these effects with sugar. A few studies seem to suggest that sugar itself has more of an expectancy effect on childrens’ behavior – where parents and teachers expect sugar to impact on childrens’ behavior. On the other hand, we know that the sugar in our foods isn't it good for kids and we still don’t know what the long term effects of chronic intake of sugar are.
Do people with ADHD eat differently compared to people without ADHD?
We don't really know. The response to a handful of studies on this topic suggests that people with ADHD might eat more unhealthy food or might eat more impulsively or might be more prone to emotional eating.
These studies are very small and I think it's still unclear. We do know from studies that I mentioned, people with ADHD do appear to have lower blood levels of nutrients like omega 3. However, we don't know if that's due to less intake or due to a different metabolism.
Is there such thing as a diet for ADHD?
There are certainly claims by the Feingold Association that the Feingold Diet can improve ADHD symptoms. This diet is essentially about excluding certain nutrients from your diet, also known as a restriction diet. There is some evidence that it may benefit some people, although not everyone.
These diets are also hard to do - they require a behavior plan. Therefore, it's not considered the standard practice to recommend these diets but we do tell families that, if they suspect diet has an impact and they think they can get enough behavioral support to do it, then it could be worth a try.
Should people with ADHD control their caffeine intake?
This is a difficult question. Some people with ADHD do report that caffeine helps them because caffeine is a stimulant. It's pharmacological action is not the same as therapeutic medications, but it is a cortical stimulant.
There's a small amount of literature which questions whether the chemicals within caffeinated foods and drinks actually could help in terms of the pharmacological effect for ADHD. It's difficult to tell those who benefit from using caffeine to cut back when it seems to be helping them.
On the other hand, you can make matters worse if you're getting jittery and anxious – caffeine can worsen those symptoms. My advice is to encourage those with ADHD to experiment with their caffeine intake. Try cutting it back to see if they feel better, especially if they're drinking excessively or if they’re not sleeping well. We know that poor sleep is a big factor in ADHD. Caffeine affects people in different ways; it's surprising how little caffeine it can take to disrupt sleep for some people.
How can you encourage children to start eating a healthier diet?
I recommend a gradual approach to offer only healthy foods and then gradually removing opportunities to eat unhealthy foods. It’s important to give kids options and not have one option be healthy and another be unhealthy. They need two or three healthy options, so you don't need to worry about what they eat or whether it's healthy or not. By doing this gradually the child can learn to get used to it.
Are there any symptoms that could inform us that someone with ADHD has an unbalanced diet?
In my opinion, no. There have been efforts to determine if people with ADHD with a lot of skin rashes or allergic reactions especially benefit from an ADHD related diet but it doesn't seem to be correlated. It doesn't seem that individuals with ADHD with allergies are the subgroup that needs dietary changes per se. I think it remains unclear.
In the emerging field of dietary psychiatry, we’re moving towards measuring the levels of nutrients in the blood and most people in the United States are not getting their minimum daily requirements - the same is true for the ADHD population. Although blood tests give us an indication of overall health they do not show how this affects behavior. The only way to understand that is to experiment carefully with modifications to a person’s diet and make observations.