A large study of Swedish adult twins looked at whether attention and hyperactivity symptoms were linked to what people ate. The people were aged 20 to 47, and their ADHD symptoms were self-reported scores, not clinical diagnoses. Diet was measured with a food questionnaire that only about a third of the group filled in.
Among the 8,731 adults with diet data, more attention problems went along with slightly more high-sugar food and with a bit more seafood, high-fat, high-protein and unhealthy food. More attention problems also went along with slightly less fruit and vegetables. Hyperactivity and impulsivity showed the same pattern but even weaker. The authors described all of these links as small.
When the researchers accounted for both kinds of symptoms at the same time, attention problems still tracked with high-sugar food and unhealthy food, while the hyperactivity links nearly disappeared.
Twin modeling suggested the overlap came from both shared genes and each twin's own separate experiences. Comparing identical twins hinted at a possible causal link, but the study could not test which way it ran.
The results are cross-sectional, and the people who reported their diet were not typical of the whole group, so the findings may not apply broadly.
The numbers Stats and what the terms mean
The statistics behind the plain-language claims above.
- Li, 2020: links between attention problems and high-sugar food r = 0.13, fruit r = -0.07 and vegetables r = -0.06; after accounting for both kinds of symptoms, high-sugar food r = .10 and unhealthy food r = .09.
What the terms mean:
- r is a correlation, from -1 to 1. 0 means no link, and values nearer -1 or 1 mean a stronger link.
Source: Li L, Taylor M, Bälter K, et al.. Attention‐deficit/hyperactivity disorder symptoms and dietary habits in adulthood: A large population‐based twin study in Sweden. American Journal of Medical Genetics Part B: Neuropsychiatric Genetics (2020). doi:10.1002/ajmg.b.32825