Basic Science and Pathogenesis.

Background: Clinical studies indicate that mid-life dietary patterns are a risk factor for cognitive decline. Adherence to a Mediterranean diet (MeDi) may promote healthy brain aging in contrast to a Western diet (WD), yet these diets have not been examined in pre-clinical models. We hypothesized that consumption of the MeDi would have better cognitive performance compared to the Western diet in middle-aged rats.

Method: A subset of animals that provided diet-specific fecal samples were used in this pilot study. Four-month-old male Fischer 344 rats were randomly assigned to a MeDi (n = 13) or WD (n = 7) for approximately one year. Animals then underwent neurobehavioral assessments including the Y-maze, Morris water maze, and water radial arm maze to assess aspects of short- and long-term memory. Data were analyzed via Student's T-test or Two-Way Repeated Measures ANOVA where appropriate.

Result: For the Y-maze, there was no difference in percent correct alternations between diet groups (p = 0.24), but the MeDi group had more total alternations compared to the WD group (p = 0.04). For the Morris Water Maze, the MeDi group had a decreased latency compared to the WD group (p = 0.03). Additionally, there was a Day x Diet Effect where the MeDi group had a decreased latency on days 3-5 (p ≤ 0.01) compared to the WD group. There was no difference between diet groups for platform probe testing (p = 0.80). For the water radial arm maze, there was no difference in total (p = 0.56), working memory correct (p = 0.73), or working memory incorrect (p = 0.33) errors between diet groups. However, the WD group committed more reference memory errors compared to the MeDi group (p = 0.01).

Conclusion: Middle-aged animals consuming a MeDi demonstrated better aspects of learning and memory compared to animals consuming a WD. This data helps support clinical data suggesting that mid-life dietary patterns impact cognitive function.