Popular daily snack found to boost brain blood flow in older adults, new study shows

Eating a daily serving of peanuts may help older adults improve blood flow to their brains and boost memory, according to new research.

In a study published in Clinical Nutrition, scientists at the NUTRIM Institute at Maastricht University Medical Center in the Netherlands set out to test whether this simple, inexpensive food could make a measurable difference in people's brains as they age.

The team recruited 31 healthy older adults between the ages of 60 and 75. In one period of the study, participants ate 60 grams of unsalted, skin-roasted peanuts every day for 16 weeks. In another stage, they avoided peanuts entirely, according to a press release.

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The order was randomized, and there was an eight-week break in between the two periods so that the effects of the first period wouldn’t carry into the second.

Throughout the study, researchers measured blood flow in the brain using specialized MRI technology and tested memory using a standard set of cognitive measures.

At the end of the peanut consumption period, the results showed that blood flow in the brain increased by 3.6% overall. There were also slightly stronger improvements in gray matter, which is the brain tissue responsible for memory, emotion and decision-making. 

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"[Cerebral blood flow] is an important physiological marker, because having a strong flow of blood to the brain contributes to its health," Peter Joris, Ph.D., the study's author and an associate professor in the Department of Nutrition and Movement Sciences at the Maastricht University Medical Center, said in the press release. 

"We found that longer-term consumption of unsalted, skin-roasted peanuts improved global cerebral blood flow, which suggests an overall enhancement in brain vascular function."

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These increases were most notable in the frontal and temporal lobes, areas that are important for higher-level thinking and language.

Participants also performed better in verbal memory tests, by approximately 5.8%.

Other areas of thinking, like executive function and reaction speed, did not show meaningful improvement.

The study also reported small decreases in systolic blood pressure and pulse pressure, suggesting broader benefits to vascular health.

Peanuts contain several nutrients that may support blood vessel function, including unsaturated fats, plant protein, fiber, polyphenol and certain amino acids, the study authors noted.

"Peanuts are especially rich in plant-based protein and contain high concentrations of L-arginine, an amino acid important for vascular health," Joris wrote. "They are also a valuable source of unsaturated fats and polyphenols, both known to support vascular function."

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Because the peanuts were roasted with their skins on, participants also consumed additional antioxidants. Together, these components may help explain the improvements seen in blood flow and memory.

The study did have some limitations, including the small sample size and the fact that all participants were healthy older adults. That makes it difficult to determine whether the effect would hold true in larger groups, younger people and those with medical conditions.

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The study also tested only unsalted, skin-roasted peanuts at a specific daily amount. Other forms of peanuts or smaller servings may not produce the same results. 

Because participants likely knew whether they were eating peanuts, there is also the possibility of a placebo effect, the researchers noted.

The trial lasted only a few months, so it cannot show whether these benefits last over time or affect long-term dementia risk.

As peanuts are dense in calories, nutritionists generally recommend choosing unsalted, lightly salted, dry-roasted or raw peanuts rather than heavily salted or oil-roasted variants. Moderate servings of peanuts should be balanced with healthy proteins, vegetables, fruits and whole grains.

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The NUTRIM study was supported by funding from The Peanut Institute Foundation, although the foundation did not have a role in the study design, implementation, analysis or interpretation of the data or the writing of the manuscript, the published results noted.