A simple bowl of peanuts placed on the living room table could do more than satisfy a little hunger pangs. Dutch researchers looked into this very common snack to see if it could act on the brain, particularly on the memory of the elderly, as cognitive decline and dementia increasingly worry families. And the results are surprising!
Two handfuls of peanuts a day!
The study was conducted by the Institute of Nutrition and Translational Research in Metabolism (NUTRIM) at Maastricht University Medical Center, the Netherlands. 31 healthy men and women, aged 60 to 75, participated in a randomized crossover trial: a period of 16 weeks with 60 g of peanuts per day, another of 16 weeks without peanuts or other nuts, separated by an eight-week break in order to compare the two situations in each person. The trial was carried out in healthy individuals, non-smokers and without diabetes or cardiovascular disease, in a context where dementia is increasing sharply on a global scale, with an estimate of 78 million people affected in 2030 and 139 million in 2050.
During the “peanuts” phase, participants received pre-measured sachets of 60 g of unsalted peanuts, roasted with the skin, or about two good handfuls, to consume in the morning or afternoon, in one or more times, possibly added to meals. Their diet remained regulated, without other nut-based products, and their physical activity and sleep were monitored. At the end of each 16-week period, the volunteers underwent a brain MRI, as well as a battery of computerized cognitive tests, the Cambridge Neuropsychological Test Automated Battery.
What the researchers measured
With peanuts, overall cerebral blood flow increased by 3.6%, gray matter blood flow by 4.5%, with larger increases in the frontal lobe, by 6.6%, and the temporal lobes, by 4.9%, key regions for language and verbal memory. “Cerebral blood flow (CBF) is an important physiological marker of cerebrovascular function. It corresponds to the quantity of blood which irrigates the brain, providing it with oxygen and nutrients essential to its health.explains Dr. Peter Joris, author of the study and associate professor at the Department of Nutrition and Movement Sciences (NUTRIM) at the University Medical Center Maastricht.
In terms of performance, the researchers observed progress on a verbal memory test: during the delayed recall of a list of 18 words, after 20 minutes, the participants identified on average 1.4 more words, or a gain of 5.8%, during the period with peanuts compared to the period without. At the same time, systolic blood pressure fell.
“For the first time, we demonstrated that peanut consumption improved cerebrovascular function in healthy older adults. These beneficial effects could explain the improvements observed in memory, and shed new mechanistic light on how regular consumption of peanuts can have a positive effect on cognitive functions.explains Joris.
Why does this snack support memory?
To interpret these results, the team recalls that peanuts, often listed with nuts in dietary recommendations, are very nutritionally dense. 60 grams of roasted peanuts with the skin provided approximately 340 kcal, 15.5 g of proteins, 29.5 g of mostly unsaturated lipids, 9.7 g of carbohydrates and 5.1 g of fiber. “For this study, roasted peanuts with the skin on were chosen because peanut skin contains additional dietary fiber and natural plant compounds, specifically antioxidants. Together, these nutrients may help explain the beneficial health effects of roasted peanuts with the skin observed in this study.“, said Peter Joris.
The authors also highlight the richness of peanuts in L-arginine, an amino acid precursor of nitric oxide involved in the dilation of blood vessels, and the presence of polyphenols, including resveratrol and flavonoids concentrated in the skin, likely to support vascular function.
But be careful, the researchers specify that these results specifically concern unsalted peanuts, roasted with the skin, consumed in a very controlled setting, and that this type of energy-rich snack is not suitable for people with peanut allergies.