Eating peanuts every day improved brain insulin response in older adults, study finds

A small trial with a surprising result

Scientists at Maastricht University Medical Center have reported that eating peanuts every day improved how a part of the brain responds to insulin in older adults. The findings were publicised on 1 November 2026 through a release headlined "Scientists discover a surprising brain benefit of eating peanuts every day" [1]. The study itself was published in Food & Function, and EurekAlert lists the journal article as published on 30 September 2026 [2].

Many readers want two things: to know whether the claim is real, and to know whether it means they should change their diet. The honest answer to the first is that the result is interesting. The answer to the second is that a single trial of 31 people cannot settle the question.

Who took part and how the trial ran

The participants were 31 healthy adults aged 60 to 75 [1] [2]. The research is described as a randomised, controlled crossover trial [1]. Participants ate about 60 grams of peanuts every day for 16 weeks, which the researchers describe as approximately two servings [1]. The work was carried out in the NUTRIM research institute of Maastricht University Medical Center [2].

What the researchers measured

The measurement was brain blood flow, not a clinical test of memory. The researchers used arterial spin labelling MRI (ASL-MRI), which measures regional blood flow, and they assessed brain insulin responsiveness from changes in regional blood flow after participants received insulin through the nose [2] [1].

Daily peanut intake improved that response in the lingual gyrus, the hippocampus, the parahippocampal gyrus and the posterior cingulate gyrus, all in the right hemisphere [1] [2]. The EurekAlert release's figure caption also lists the thalamus [2]. The senior author is Dr Peter Joris, an associate professor at Maastricht University Medical Center. He is quoted as saying: "The hormone insulin plays an important role in the brain, where it supports memory and other cognitive processes" [1]. That sentence explains why insulin signalling in the brain was measured. It does not report a change in memory performance in this trial.

The release does not give an effect size for the insulin response [1]. That matters, because a result can be statistically clear and still small in practice, and the release does not say how large the change was.

An earlier study cited in the release

The release refers to earlier work, which it reports as finding that peanut consumption increased overall cerebral blood flow by 3.6% and improved verbal memory performance by 5.8% [1]. These are percentage changes. The release reports no standardised effect size for them either [1].

Who paid for the research

The study was funded by The Peanut Institute Foundation [1] [2]. The release says the foundation had no involvement in designing or conducting the study, analysing or interpreting the results, or preparing the manuscript [1]. The release itself was issued by The Peanut Institute [1].

Those statements do not make the findings wrong. They do mean that the headline comes from an organisation linked to peanuts, and that readers should weigh the claims with that in mind.

Why the result matters, and what it does not show

The result is interesting because it comes from a controlled trial rather than a survey. The trial found a change in how brain regions respond to insulin, measured with brain imaging after insulin was given through the nose [2].

What the study does not show is equally important. The trial measured a brain-imaging response, not a clinical outcome, and it involved 31 people followed for 16 weeks [1] [2]. On those facts, the study cannot show that peanuts prevent memory loss or protect against dementia. People managing diabetes or another medical condition, or following a restricted diet, should speak to a doctor before changing their diet on the basis of a press release.

What to watch next

The release gives no effect size for the insulin response, so the most useful next step is to read the full paper for the size of the change [1]. A fuller report would also show whether the brain changes link to any memory outcome, which the release does not measure directly.

Readers who want to follow the story should look for the full journal article. For now, the study is best read as a promising signal from a small trial, funded by a peanut-linked foundation and announced with a headline that goes further than the data.