Thirty-one volunteers in Maastricht, all between 60 and 75, spent 16 weeks eating about 60 grams of plain roasted peanuts every day. For another 16 weeks they ate none. In between, they went through a series of brain scans, and at the end the researchers had a small but interesting result: in the peanut phase, parts of the brain involved in memory responded better to insulin.
That sentence needs some unpacking, because “brain” and “insulin” in the same headline can send people towards conclusions the study does not support. So here is what was actually done, what it found, and what it leaves open.
What the Maastricht team did
The trial came from the NUTRIM research institute at Maastricht University Medical Center in the Netherlands, led by Peter Joris with first author Lucia Kerkhof, and it was published in the journal Food & Function (2026, volume 17, issue 20, DOI 10.1039/D6FO03208G). It was a randomized crossover design, which means every participant did both versions of the diet, in random order, and acted as their own comparison. That is a useful setup for a small study, because differences between people matter less when the same person is compared with themselves.
In the peanut phase, volunteers received premeasured packets of unsalted, skin-on roasted peanuts, roughly two servings a day. They could eat them whole, spread them across the day or stir them into meals. In the control phase they simply left peanuts out. According to the trial registry entry, a washout period of at least eight weeks separated the two phases.
The measurement is the unusual part. Insulin is best known for moving sugar out of the blood, but the brain has insulin receptors too, and insulin signalling there is linked to memory and other thinking tasks. To test how well the brain responds, the researchers gave participants a dose of insulin through the nose and then used MRI to track changes in blood flow in different brain regions. A stronger blood-flow response after the insulin is read as better brain insulin responsiveness.
What they found
After the peanut phase, the response was better in several regions on the right side of the brain: the hippocampus, the parahippocampal gyrus, the lingual gyrus and the posterior cingulate gyrus. These areas are tied to memory and to how the brain files and retrieves information. The authors wrote that daily peanut intake “beneficially affected insulin responsiveness in memory-related brain regions in older adults.”
The same group had earlier reported, from the same 16-week peanut diet, a 3.6 percent rise in overall cerebral blood flow and a 5.8 percent improvement in verbal memory (Clinical Nutrition, 2025). Those two figures come to us through the press material for the new paper, so treat them as reported rather than independently checked.
This is not the first time the group has seen something like this. In a 2024 trial in the American Journal of Clinical Nutrition, 28 older adults with overweight or obesity ate 60 grams a day of mixed nuts (walnuts, pistachios, cashews and hazelnuts) for 16 weeks. Brain insulin action improved in five clusters of the frontal and occipital lobes, while insulin sensitivity in the rest of the body did not change. Liver fat, LDL cholesterol and systolic blood pressure were lower after the nut period. Body weight stayed the same.
So there is a pattern across two small trials from one lab. Patterns from one lab are worth noting, and they are also exactly what independent teams need to test.
What the research does not show
It does not show that peanuts prevent dementia or Alzheimer’s disease. Nobody in the trial was followed for years to see who developed memory loss, and the volunteers were healthy. A change in how a brain region’s blood flow responds to nasal insulin is a biological marker. Whether that marker translates into sharper memory in daily life, or any protection later on, is still unknown.
It does not show that peanuts are special. The 2024 trial used mixed tree nuts and saw a similar signal, and the authors of the new paper suggest several components of peanuts, such as unsaturated fats, fibre, minerals and the amino acid arginine, might play a part. Which one matters, if any, has not been established.
It is also a small study from a single site, and it was funded by The Peanut Institute Foundation, which also issued the press release that most news coverage was built on. The researchers state that the funder had no role in the design, running, analysis or writing of the study, and the trial was registered in advance (NCT05724654), which is good practice. Even so, industry-funded nutrition research is best read alongside independent work, and the 2024 nut trial was likewise paid for by a nut trade body, the International Nut and Dried Fruit Council.
Finally, a control phase of “no peanuts” tells us about adding peanuts, not about swapping them for something else. A person who replaces a bag of crisps with peanuts is in a different position from one who adds 340 or so extra calories on top of everything they already eat. (That calorie figure is a rough estimate for 60 grams of plain roasted peanuts; check your own pack.)
Fitting this into an ordinary week
Nothing here suggests you should start eating two handfuls of peanuts tomorrow because a news story said so. But the findings fit comfortably with what is already commonly advised: whole, minimally processed foods tend to serve long-term health better than packaged snacks. Plain peanuts are a very different product from honey-roasted, heavily salted or sugar-coated versions, and the study used unsalted ones for a reason. If you want a sense of where flavoured snack foods land in the research, our piece on ultra-processed foods and what the research shows covers it.
Insulin is also a useful thread to pull on more generally. How well the body, and apparently the brain, responds to it depends on food, sleep, activity and body composition together, not on one snack. We explain the wider picture in how metabolic flexibility works. And since movement is one of the better-supported things for both blood sugar and brain health, a short interval-style walk after meals is a cheap companion to any dietary change.
A few practical notes if you do want to try peanuts. Peanut allergy is serious and can be severe; if you or anyone in your household has one, none of this applies to you. Whole peanuts are a choking risk for small children and for people with swallowing difficulties. And if you are managing diabetes, kidney disease or a calorie-controlled diet, talk with your doctor or dietitian before adding a daily 60 grams of anything.
Eaten plain, in modest amounts, peanuts look like a sensible snack with some intriguing early evidence behind them. Larger and longer trials, ideally from teams with no link to the industry, will show whether the brain signal turns into something people can feel.
This article is for general information only and is not medical advice. Speak to a qualified health professional before changing your diet, especially if you have a medical condition or allergy.