Daily peanuts improved brain insulin response and memory in older adults, two trials find

Two clinical trials from the same Dutch research group have found that eating roughly two handfuls of unsalted, skin-roasted peanuts every day for 16 weeks measurably changed how the aging brain works — improving blood flow, verbal memory, and, in a newer study, the brain's responsiveness to insulin in regions tied to memory.

The research, led by Associate Professor Peter J. Joris and Ph.D. candidate Lucia Kerkhof at Maastricht University Medical Center's Institute of Nutrition and Translational Research in Metabolism (NUTRIM), was conducted as randomized, controlled crossover trials — a design in which each participant serves as their own control, reducing the noise caused by individual differences.

The first trial, published in the peer-reviewed journal Clinical Nutrition, enrolled 31 healthy adults between 60 and 75 years old. Participants ate 60 grams of peanuts daily during one 16-week period and avoided peanuts entirely during another, with an eight-week washout phase in between. Using pseudo-continuous arterial spin labeling MRI — a non-invasive imaging technique that measures blood reaching brain tissue without radiation or contrast dyes — researchers found that global cerebral blood flow increased by 3.6 percent compared to the control period. In gray matter specifically, the increase was 4.5 percent. Blood flow rose 6.6 percent in the frontal lobes and 4.9 percent in the temporal lobes, areas involved in memory, language, and executive control. Verbal memory performance improved by 5.8 percent.

We were intrigued to see improvements not only in specific brain regions, but also at the whole-brain level. That indicates a more widespread effect on brain vascular function than what we observed in earlier studies.— Peter J. Joris, Associate Professor, NUTRIM, Maastricht University Medical Center

A second study, published in the peer-reviewed journal Food & Function, examined a different mechanism: how the brain responds to insulin. Insulin is best known for regulating blood sugar, but it also helps nerve cells grow, survive, and communicate, supporting memory and other cognitive abilities. As people age, the brain can become less responsive to insulin — a change linked to cognitive decline and processes associated with Alzheimer's disease. Researchers measured this by tracking changes in regional cerebral blood flow after insulin was administered through the nose, using arterial spin labeling MRI. After 16 weeks of daily peanut consumption, they observed improved insulin responsiveness in a cluster of brain regions in the right hemisphere, including portions of the lingual gyrus, hippocampus, parahippocampal gyrus, and posterior cingulate gyrus.

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.— Dr. Peter Joris, Senior Author and Associate Professor, Department of Nutrition and Movement Sciences, NUTRIM, Maastricht University Medical Center

Why peanuts specifically? The researchers point to several overlapping nutrients rather than a single ingredient. Peanuts are dense in unsaturated fatty acids, dietary fiber, vitamins, minerals, and bioactive phytochemicals. The peanut skin — preserved in skin-roasted varieties — is rich in polyphenols including resveratrol, which has antioxidant properties that may support vascular health. Peanuts are also a strong source of L-arginine, an amino acid that the body uses to produce nitric oxide, a molecule that relaxes blood vessels and regulates blood flow and has been reported to facilitate learning and memory performance.

Multiple nutrients present in peanuts, including unsaturated fats, dietary fiber, vitamins and minerals and bioactive phytochemicals, could potentially contribute to the observed brain benefits. Peanuts are also a good source of plant-based protein and are especially rich in L-arginine. L-arginine is a key precursor of nitric oxide (NO), which has been reported to facilitate learning and memory performance.— Dr. Peter Joris, Associate Professor, NUTRIM, Maastricht University Medical Center

The researchers also noted the broader public health context motivating the work. Dementia is currently ranked as the seventh leading cause of death worldwide by the World Health Organization, and the number of people affected by age-related cognitive decline is increasing rapidly. Peanuts, Joris noted, are widely consumed and affordable — factors that matter if dietary findings are ever to translate into practical guidance.

The results are not without important caveats. Both trials involved only 31 participants — a small sample — and were funded in part by The Peanut Institute Foundation, an industry-linked body. The researchers stated the foundation had no involvement in designing or conducting the studies, analyzing results, or preparing the manuscripts. Larger, longer-term studies are needed to confirm the benefits and establish how broadly they apply.

Why it matters — With dementia cases rising globally and no proven pharmaceutical prevention, these trials add peer-reviewed evidence that an affordable, widely available food may support brain vascular health and memory in older adults — though the small sample sizes and industry funding mean the findings need replication in larger studies before they can inform dietary guidance.

Reported by sciencedaily.com, psypost.org, frontiersin.org