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In a randomized crossover trial, older adults who ate 60 grams of unsalted, skin-roasted peanuts daily for 16 weeks showed a different brain blood-flow response after intranasal insulin in several right-hemisphere regions. The measure is an indirect indicator of brain insulin responsiveness, and the small study does not establish that peanuts improve memory or prevent cognitive decline.
A 16-week randomized crossover trial found that older adults who ate 60 grams of unsalted, skin-roasted peanuts daily had a different blood-flow response to intranasal insulin in parts of the brain associated with memory. The finding, published in Food & Function, suggests a possible link between diet and brain insulin responsiveness, but it does not show that peanuts improve memory or prevent cognitive decline.
Researchers compared a 16-week peanut-eating period with a 16-week period without peanuts or other nuts. The 31 participants who completed the study had a mean age of 67. Each person completed both periods in randomized order, separated by an eight-week washout. The trial was single-blind and controlled, according to the study report.
At the end of each period, researchers used arterial spin labeling MRI to measure cerebral blood flow before and after intranasal insulin. They treated the change in blood flow as an indirect measure of regional brain insulin responsiveness, not as a direct measurement of insulin signaling in neurons. After the peanut period, a region in the right hemisphere—primarily involving the lingual gyrus, hippocampus and parahippocampal gyrus—showed a significantly lower blood-flow response to insulin than after the control period.
The report says 36 people were randomized and 31 completed the trial: 15 women and 16 men. Peanut intake was generally well tolerated, with high compliance; one participant withdrew after gastrointestinal discomfort. Body measurements remained stable, while total energy intake rose during the peanut period and dietary composition shifted toward more unsaturated fat and fiber and less carbohydrate, saturated fat and cholesterol.
What the Brain Blood-Flow Finding Shows
The result adds evidence to a question about whether foods can affect how brain regions respond to insulin. Insulin has roles in brain activity beyond its familiar role in regulating blood sugar, and the regions examined are involved in memory and other cognitive or metabolic functions. A change in the measured response may help researchers investigate those links.
However, the study does not establish that the observed change is beneficial. The reported lower blood-flow response cannot by itself be interpreted as improved insulin function, better cognition or reduced disease risk. The MRI outcome was an indirect physiological measure, and the trial report does not establish that the brain response caused a memory change. Readers should treat the finding as an early research result, not a dietary recommendation or a clinical outcome.
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How Researchers Tested Peanut Intake
The trial follows earlier research, described in the study report, suggesting that daily skin-roasted peanut consumption may benefit brain vascular function and memory in older adults. The new analysis asked whether changes in brain insulin responsiveness could be related to those previously reported cognitive findings. It examined the response after a sustained dietary intervention rather than testing a single meal.
Participants were aged 60 to 75, had a body mass index between 20 and 35, and met eligibility criteria that excluded peanut allergy and several major health or medication factors. Researchers supplied prepackaged portions and asked participants to avoid peanuts and other nuts during the control period. The sample was limited to people who met these specific criteria, so the results may not apply to all older adults.
“Brain insulin responsiveness refers to how specific brain regions adjust neuronal activity in response to insulin.”
— The study authors, as described in the News-Medical report
Limits of the Trial Results
The available report does not provide enough information to determine whether the blood-flow difference led to measurable changes in memory, daily functioning or long-term brain health. It also does not establish why the response was lower in the identified region or whether that pattern should be considered beneficial. The reported result is specific to the measured regions and study conditions.
The study was small, with 31 completers, and enrolled a selected group of adults without certain major conditions. The intervention also increased energy intake and changed several dietary components, so the effect cannot necessarily be attributed to peanuts alone or to one nutrient. The supplied report does not state the size of the blood-flow difference or provide enough detail to assess its clinical importance.
Questions for Larger Follow-Up Studies
Further research would need to test whether these MRI findings can be reproduced in larger and more diverse groups, and whether they track with changes in cognitive performance over time. Studies could also examine whether the response varies with the amount or form of peanuts consumed, or with participants’ metabolic health.
For now, the next step is interpretation and replication rather than a change in clinical guidance. The trial provides a physiological observation; it does not establish a proven strategy for maintaining memory or treating insulin-related disorders.
Key Questions
What did participants eat?
They ate 60 grams of unsalted, skin-roasted peanuts each day during the 16-week intervention period.
What changed in the brain measurement?
After the peanut period, MRI showed a significantly lower blood-flow response to intranasal insulin in a right-hemisphere cluster that included the lingual gyrus, hippocampus and parahippocampal gyrus. The measure was an indirect indicator of regional responsiveness.
Does the study prove peanuts improve memory?
No. The reported result concerns an insulin-related blood-flow measure. It does not establish that the change improved memory or prevented cognitive decline.
How many people completed the trial?
Thirty-one participants completed the study, out of 36 who were randomized.
Can the result be applied to everyone?
The trial involved a small, selected group of adults aged 60 to 75 who met specific eligibility criteria. Further research is needed before assuming the findings apply to broader populations.
Source: news-medical.net
