Healthier diet patterns tend to be associated with improved focus & attention relative to western-style diets rich in saturated fat and refined sugar. High intakes of fish and plant-based foods were associated with increased measures of attention among elderly people in one cross-sectional study.[1] Observational studies of children and young adults with ADHD have also found links between focus & attention ability and healthier diet patterns. Moreover, overall less-healthy diet patterns have been associated with decreased focus & attention in these age groups.
The effect of an unhealthy diet on focus and attention may also be acute, as suggested by one study that found consumption of a 5- or 7-day high-fat diet was sufficient to impair focus & attention in both healthy[2] and sedentary[3] adults.
However, most of the evidence on the effect of diet on focus & attention tends to be observational in nature, and overall results have been mixed. More research is needed to determine whether there is a causal relationship between diet and focus & attention in different populations.