Abstract
Past research indicates that dietary alterations involving increases in nuts or beetroot, or decreases in salt, may have the potential to enhance cognitive functioning. The current study reports cognitive outcomes from a 12-week randomized controlled parallel intervention trial designed to evaluate the effectiveness of manipulating these ingredients in a dietary staple, bread. Participants were recruited from Dunedin, New Zealand, between February 2015 and March 2017. Initial inclusion criteria required at least one indicator of metabolic syndrome and daily consumption of at least six slices of bread, but these criteria were relaxed 6 months into the study due to recruitment difficulties. In total, 196 participants were randomized (using minimization by age group, sex, and body mass index) to consume one of four breads (hazelnut, beetroot, low salt, or a control white bread). Participants completed a computerized cognitive test battery and physiological testing at four points during the intervention. Analyses focused on 102 participants (aged 18–73 years) who finished the intervention and completed pre- and post-intervention cognitive testing. Participants who consumed the experimental breads showed no evidence of cognitive improvement relative to the control group. Furthermore, the expected physiological changes did not occur, and participants reported poor compliance. Our findings suggest that participants may have changed their eating habits during the intervention period such that they consumed less bread and ingested other counteracting nutrients, rendering the intervention ineffective. Insight from this study can be used to guide the design of future dietary interventions.