Objective:

To assess whether daily peanut consumption affects brain insulin responsiveness and related metabolic measures in older adults.

Approach:

• Design and participants: Randomized, single-blind, controlled crossover trial; 31 adults aged 60–75 completed both study periods.
• Interventions: Participants consumed 60 g of unsalted, skin-roasted peanuts daily for 16 weeks and had a 16-week control period without nuts, separated by an 8-week washout.
• Assessments: Researchers measured cerebral blood flow before and 30 minutes after intranasal insulin using arterial spin labeling MRI, alongside metabolic measures and associations with verbal recognition memory.

Key Findings:

• Peanut consumption was associated with a statistically significant reduction in insulin-induced cerebral blood flow in one right-hemisphere cluster (mean difference −5.4 mL/100 g/min; volume 552 mm³), spanning portions of memory-related regions.
• No significant differences were found in global, gray matter, cortical, or subcortical brain responses; regional changes were not significantly associated with previously reported improvements in verbal recognition memory.
• Liver fat, fasting glucose, insulin, insulin resistance, cholesterol, and high-sensitivity C-reactive protein did not change significantly. Triglycerides were lower at week 8, but not at week 16.
• Median adherence was 100%. One participant withdrew because of gastrointestinal discomfort; no study-related serious adverse events were reported.

Interpretation:

The authors described the findings as a potentially beneficial effect on regional brain insulin responsiveness, but the study did not establish that these changes contributed to verbal recognition memory improvements.

Limitations:

• The small sample limited analyses of associations between brain responses and cognitive outcomes.
• Insulin-induced cerebral blood flow is an indirect measure and does not directly establish neuronal insulin signaling.
• The control period was not matched for energy or macronutrients, and participants added peanuts without prescribed food replacement, so changes in overall dietary intake could partly explain the findings.

Conclusion:

In this trial, 16 weeks of daily peanut consumption was associated with a region-specific change in insulin-induced cerebral blood flow in older adults; broader brain and metabolic measures were largely unchanged.

Sources:

• Food & Function study (as described in the supplied article context)