Clinical Nutrition: Roasted Peanuts with Skins Improve Blood Flow in the Brain

Regular consumption of unsalted roasted peanuts with their skins improves cerebral blood vessel function and enhances memory in older adults, according to researchers at Maastricht University. The study was published in Clinical Nutrition.

Problems with cerebral blood supply are among the key physiological markers of age-related cognitive decline. Reduced delivery of oxygen and nutrients impairs neuronal function and is associated with an increased risk of dementia. For this reason, scientists are actively investigating how lifestyle and diet influence vascular brain health.

Although peanuts are botanically legumes, their nutritional profile resembles that of nuts: they contain plant protein, unsaturated fats, fiber, and numerous bioactive compounds. One motivation for the study was the high level of L-arginine — an amino acid involved in the production of nitric oxide, which dilates blood vessels and regulates blood flow. Peanut skins are rich in polyphenols, including resveratrol, known for its antioxidant properties.

The experiment involved 31 healthy volunteers aged 60 to 75. It was conducted as a randomized controlled crossover trial: each participant completed two 16-week phases — one with daily consumption of 60 grams of roasted peanuts with their skins, and one without peanuts. The phases were separated by an eight-week washout period.

The researchers assessed cerebral vascular function using a noninvasive MRI method that measures blood-flow volume without contrast agents or radiation. Cognitive performance was evaluated with computer-based neuropsychological tests.

After the peanut-consumption phase, total cerebral blood flow increased by 3.6%, and blood flow in grey matter rose by 4.5%. The most significant changes were observed in the frontal lobes (a 6.6% increase) and temporal lobes (4.9%) — regions involved in memory, language, and executive functions.

As cerebral circulation improved, cognitive performance also increased: participants showed a 5.8% improvement in verbal-memory tests. During delayed recall tasks, they remembered and recognized more words than during the control phase.

Dietary effects also appeared in cardiovascular measures. Systolic blood pressure decreased by an average of 5 mm Hg, and pulse pressure by 4 mm Hg. Despite the added caloric intake (about 340 kcal per day), body weight did not change significantly — researchers suggest that participants may have intuitively compensated for the extra calories by eating less of other foods.

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