Peanuts and the brain’s response to insulin: a localized signal in older adults

A trial comparing two periods in the same participants

The participants, whose average age was 67, completed two periods in a randomized order: one with 60 g per day of unsalted peanuts, roasted with their skins on, and the other without peanuts. Each period lasted 16 weeks, with an eight-week interval between them.

This crossover design allows each person to serve as their own control. The trial is described as single-blind, but the abstract provided does not specify who was unaware of the intervention assignments.

To assess the brain’s response to insulin, the researchers used MRI to measure changes in blood flow in the brain after insulin was administered through the nose. This is a physiological indicator, not a direct memory test.

A regional change, not a whole-brain effect

The whole-brain analysis identified a region in the right hemisphere where the blood flow response to insulin was reduced after the peanut period compared with the control period. The proposed anatomical location includes areas linked to memory.

The authors present this decrease as a potentially beneficial effect on the brain’s response to insulin. However, a reduction in this vascular response is not, in itself, evidence of cognitive improvement. The abstract does not allow a detailed assessment of the evidence supporting this interpretation.

No changes were observed in liver fat or in the blood markers studied for glucose regulation, lipid metabolism and low-grade systemic inflammation. The observed signal therefore remains localized, with no general metabolic improvement detected on these measures.

A possible mechanism, not a recommendation

The researchers note that they previously reported an improvement in memory with this peanut consumption. Here, they aim to explore a possible mechanism. However, the source material does not provide detailed results from that earlier analysis, making it impossible to assess the size of the effect or its clinical relevance.

This trial therefore offers a lead on the link between diet and the brain’s response to insulin. It is not enough to recommend this quantity of peanuts to preserve memory, or to generalize the result to younger people or other preparations.

What we can take away

The interesting finding is a regional change in a brain indicator after peanut consumption. Its favorable interpretation still needs confirmation and should not be confused with a demonstrated memory benefit.