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In a randomized crossover trial, 31 adults aged 60 to 75 completed periods of eating 60 grams of unsalted, skin-roasted peanuts daily and avoiding peanuts and other nuts. After the peanut period, MRI showed a lower blood-flow response to intranasal insulin in a cluster that included the hippocampus; the study measured an indirect response, not cognitive improvement or neuronal insulin signaling directly.
A 16-week peanut-eating period was associated with a lower brain blood-flow response to insulin in a cluster of regions that included the hippocampus, according to a clinical trial in older adults. The study, published in Food & Function, used MRI blood-flow changes as an indirect measure of brain insulin responsiveness; it does not establish that peanuts improve memory or prevent cognitive decline.
The randomized, single-blind, controlled crossover trial enrolled 36 adults aged 60 to 75. Participants completed both a 16-week intervention eating 60 grams of unsalted, skin-roasted peanuts daily and a 16-week control period in which they avoided peanuts and other nuts. The periods were separated by an eight-week washout, and the order was randomized.
Thirty-one participants completed the trial: 15 women and 16 men, with a mean age of 67 and mean body mass index of 26.7. At the end of each period, researchers measured cerebral blood flow before and 30 minutes after participants received intranasal insulin. The peanut period was associated with a significantly lower blood-flow response in a right-hemisphere cluster mainly covering the lingual gyrus, hippocampus and parahippocampal gyrus.
The authors treated insulin-related changes in cerebral blood flow as a measure of regional responsiveness, not a direct reading of neuronal insulin signaling. Peanut intake was generally tolerated and compliance was reported as high. One participant left the trial because of gastrointestinal discomfort after eating peanuts; the report recorded no study-related serious adverse events.
What the Brain Scan Measured
The result adds a possible biological measure to research on diet and the aging brain. Insulin has roles in brain regions involved in memory and other functions, and researchers have been examining whether dietary patterns affect how those regions respond. A change in blood flow after insulin administration may help guide further study, but it is not itself proof of a health benefit.
The finding also needs careful interpretation: the measured response was lower after the peanut intervention in the reported cluster. The study does not establish whether that change is beneficial, harmful, or meaningful for day-to-day cognition. Nor does it show that eating peanuts treats insulin resistance, dementia, or any other condition. The trial was small and measured a brain-imaging outcome rather than a clinical outcome such as a lasting change in memory.
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How the Trial Compared Diets
Earlier work cited in the study had reported memory and brain vascular findings following daily consumption of skin-roasted peanuts. The new trial asked whether longer-term peanut intake was also associated with a change in brain insulin responsiveness. It was designed to compare each participant’s outcomes across the peanut and no-peanut periods, rather than comparing separate groups for the full study.
Participants were given prepackaged peanut portions and advised to avoid nuts and seeds with comparable nutrient profiles. Their body measurements remained stable, while the peanut period increased total energy intake and shifted the diet toward more unsaturated fat and fiber, with less carbohydrate, saturated fat and cholesterol. These dietary changes mean the trial tested a food intervention with several nutritional effects, not a single isolated peanut component.
What the Results Cannot Show
The supplied study report does not provide the size of the blood-flow difference or enough detail to judge its practical significance. It also does not establish whether the measured change persisted after participants stopped eating peanuts, or whether it corresponded to better or worse memory. The brain response was assessed through cerebral blood flow after intranasal insulin, so it should not be described as a direct measurement of neuronal insulin activity.
The sample was small and limited to selected adults aged 60 to 75 who met the study’s health and eligibility criteria. Results may not apply to people outside that group, including those with peanut allergies or significant metabolic or cardiovascular conditions. The report also describes one participant withdrawing because of gastrointestinal discomfort. Larger studies with longer follow-up and cognitive outcomes would be needed to clarify the meaning of the imaging result.
Further Trials Need Cognitive Outcomes
The immediate next step for researchers is to test whether the blood-flow finding can be replicated and determine how it relates, if at all, to measurable changes in memory or other cognitive abilities. Longer studies could also examine whether effects differ by age, health status, diet, or baseline insulin responsiveness.
For now, this trial supports a limited conclusion: daily peanut consumption was associated with a change in an indirect brain-insulin measure in a small group of older adults. It does not provide evidence that people should begin eating peanuts to improve brain health, and it does not establish a treatment effect.
Key Questions
How many peanuts did participants eat each day?
During the intervention, participants ate 60 grams of unsalted, skin-roasted peanuts daily for 16 weeks.
What changed in the brain scan?
After the peanut period, researchers found a significantly lower cerebral blood-flow response to intranasal insulin in a right-hemisphere cluster that included the hippocampus and nearby regions. Blood flow was an indirect measure of responsiveness.
Does the study show peanuts improve memory?
No. The trial assessed an MRI blood-flow response, not whether participants’ memory improved. It does not show that peanuts prevent cognitive decline.
How many people completed the trial?
Thirty-one people completed both study periods. The trial initially randomized 36 adults aged 60 to 75.
Should people eat peanuts for brain health based on this study?
The study does not establish a health benefit or recommend peanuts as a treatment. It also excluded people with peanut allergies; dietary decisions should account for individual health needs.
Source: news-medical.net
