Eating peanuts daily changed brain responses tied to memory, study finds

Researchers in the Netherlands report that eating a daily portion of roasted peanuts for four months changed how parts of the brain involved in memory respond to the hormone insulin in healthy older adults.¹ The study, from Maastricht University Medical Center, was published in the peer-reviewed journal Food & Function.¹ It involved 31 people aged 60 to 75.¹

The result is a change in brain scans, not a change in anyone’s risk of memory loss. It is also a small study, and the press release announcing it came from a peanut industry group. Here is what was measured and what remains unknown.

What happened

The volunteers ate 60 grams of unsalted, skin-roasted peanuts a day, about two servings, for 16 weeks.¹ For comparison, they also spent 16 weeks avoiding peanuts entirely.¹ After the peanut period, the researchers saw a stronger response to insulin in a group of brain regions on the right side of the brain.¹ These included parts of the hippocampus, the parahippocampal gyrus, the lingual gyrus and the posterior cingulate gyrus, areas that all play a role in memory.¹

Insulin is best known for controlling blood sugar, but it also works in the brain, where it helps nerve cells grow, survive and communicate.¹ “As people age, the brain may become less responsive to insulin, which has been linked to age-related cognitive decline,” said Dr. Peter Joris, the study’s senior author and an associate professor in the Department of Nutrition and Movement Sciences at Maastricht University Medical Center.¹

“Our study found that daily peanut consumption beneficially affected insulin responsiveness in memory-related brain regions in older adults. These findings suggest that enhanced regional brain insulin responsiveness may contribute to the cognitive benefits of unsalted, skin-roasted peanut intake.”

That is how Joris summarized the findings in the release.¹

How the study worked

The team used what is called a randomized, controlled crossover trial.¹ In plain terms, every volunteer went through both conditions, eating peanuts for one stretch and none for another, in a random order. That lets researchers compare each person with themselves rather than with a separate group. After 16 weeks, participants switched to the opposite condition.¹

To keep the amount steady, the researchers handed out premeasured packets of peanuts.¹ Volunteers were told to eat them in the morning or afternoon. They could eat the whole portion at once, spread it over the day, or add it to meals.¹

To see how the brain reacted to insulin, the team gave insulin as a nasal spray. They then measured changes in blood flow to different brain regions with a type of MRI scan called arterial spin labeling, or ASL-MRI.¹ More blood flow after the insulin was read as a sign that those areas were responding to it.¹ The researchers also used abdominal MRI scans to measure fat in the liver.¹ Thinking skills were checked with a standard set of computerized tests known as the Cambridge Neuropsychological Test Automated Battery (CANTAB).¹²

What it does not show yet

The study measured how the brain responded to insulin on a scan. The sources describing the new paper do not report whether the volunteers’ scores on the memory tests changed in this analysis, or what was found for liver fat. Some coverage went further than the data: the New York Post wrote that the brain changes suggested “the snack boosts brain power.”² The researchers themselves framed the insulin result as something that “may contribute” to cognitive benefits.¹

Several other limits are worth keeping in mind:

• Small and short. Thirty-one people were followed over two 16-week periods.¹ That is enough to spot changes in measurements, but not to say anything about memory loss or dementia over years.
• Healthy volunteers. Everyone was healthy and aged 60 to 75.¹ The results may not apply to people who already have memory problems, diabetes or other conditions.
• Which part of the peanut? The researchers do not point to one ingredient. Joris said unsaturated fats, fiber, vitamins, minerals and plant compounds “could potentially contribute.”¹ He also noted that peanuts are rich in L-arginine, an amino acid the body uses to make nitric oxide, which has been reported to help learning and memory.¹
• No blinding possible. People know whether they are eating peanuts, so this kind of food study cannot use a dummy version the way drug trials use a placebo (a dummy pill).

What came before

The new paper builds on earlier work by Joris published in 2025 in the journal Clinical Nutrition.¹ That study found that 16 weeks of eating peanuts raised overall blood flow to the brain by 3.6% and improved verbal memory performance by 5.8%.¹ Blood flow to the brain carries the oxygen and nutrients brain cells need and is seen as a sign of how healthy the brain’s blood vessels are.¹

A summary of that earlier trial, published on a peanut industry website, described the same setup: adults aged 60 to 75 alternating between eating 60 grams of skin-roasted peanuts a day and avoiding them.³ It reported that blood flow rose by about 3.6%, especially in areas linked to memory and decision making, and that systolic blood pressure (the top number) and pulse pressure showed small favorable shifts.³ The same summary noted that the study was modest in size and that the findings “do not suggest that peanuts can prevent cognitive decline.”³

Who is behind it

The research came from the Institute of Nutrition and Translational Research in Metabolism (NUTRIM) at Maastricht University Medical Center.¹ It was led by principal investigator Dr. Peter J. Joris and carried out by Ph.D. candidate Lucia Kerkhof.¹

The press release carried by ScienceDaily lists The Peanut Institute as its source.¹ The summary of the earlier trial appeared on Peanut Butter Lovers, a site that publishes peanut recipes and peanut-focused news.³ The sources given to Biohack do not say who paid for the study itself. Readers should know that the main public description of the results comes through an industry group with an interest in peanut sales, while the paper itself went through peer review at Food & Function.¹

How it fits the field

Interest in diet and the aging brain often centers on blood vessels. A nutrient-rich diet is widely described as important for protecting the brain’s blood vessels as people age, which in turn is tied to lower risk of stroke and dementia.² Peanuts are technically a legume rather than a nut, but they share many of the nutrients found in tree nuts, including plant protein and unsaturated fats.²

The insulin angle adds a second idea. Healthy insulin signaling in the brain may help protect against processes associated with Alzheimer’s disease, according to the release.¹ This study did not test that link directly. It shows that a food change over a few months can shift one measurable brain response in healthy older adults, which is an early step rather than an answer.

What to watch next

• Memory test results. Whether the CANTAB scores from this analysis, or the liver fat measurements, are reported in more detail and line up with the brain scan changes.
• Longer studies. The industry summary of the earlier trial said longer studies are underway to look at long-term effects.³ Results in more people, over longer periods, would show whether these scan changes last and whether they matter for everyday memory.
• Independent replication. So far the findings come from one research group. A test by other teams, ideally including people at higher risk of memory decline, would carry more weight.

For now, the evidence is one small, carefully controlled diet study showing a change in how memory areas of the brain respond to insulin. It does not show that peanuts prevent memory loss or dementia.