Peanut products may improve memory and anxiety in young adults Original paper

Peanuts are botanically classified as legumes but are commonly included in the nut group due to their similar nutritional composition. Nuts are rich in unsaturated fatty acids, fiber, and polyphenols, and evidence suggests that nut consumption can protect brain health and improve cognitive function.^[1] However, evidence for the effects of peanut products, specifically on cognitive function, is scarce.

In this 6-month randomized controlled trial, 63 healthy adult participants (ages 18 to 33) were assigned to one of three interventions: i) 25 grams per day of skin roasted peanuts (SRP), ii) 2 tablespoons (32 grams) per day of peanut butter (PB), or iii) 2 tablespoons per day of a control butter, which was free of polyphenols and fiber. The participants followed their habitual diets, and wine, grapes, dark chocolate, and berries were excluded due to a high content of resveratrol, a phenolic compound also present in peanuts. Nuts were also removed from the diet.

The outcomes assessed were immediate and delayed verbal memory and recognition measured by The Wechsler Memory Scale (WMS-IV), working memory and perceptual reasoning measured by the Wechsler Adult Intelligence Scale (WAIS), cognitive flexibility and visual-motor processing speed measured by the Trail Making Test (TMT), and anxiety and depression measured by The Hospital Anxiety and Depression Scale (HADS), as well as the short-chain fatty acid content in feces.

Compared to baseline, anxiety scores improved in both the SRP and PB groups, and depression scores improved in the SRP group. However, compared to the control group, the only difference was an improvement in anxiety scores in the SRP group. For cognitive function, compared to baseline, immediate memory, total verbal memory, and total memory improved in the PB group, with no significant differences compared to the control group.

For short-chain fatty acids, compared to the control group, there was an increase in acetic acid, isovaleric acid, and total short-chain fatty acids in the SRP group. Peanut polyphenol intake was found to be correlated with improvements in cognitive function, and peanut polyphenol intake and total short-chain fatty acids in feces were found to be inversely correlated with depression score.

A limitation of this study is the sample size for each group. Due to dropouts, the statistical power decreased from a calculated 80% to 60%. Other potential limitations include a lack of blinding, a peanut-free control, and funding by the Peanut Institute.