Daily Peanut Consumption Associated with Improved Memory and Decreased Levels of Stress and Anxiety

by | Feb 24, 2022 | 2021, Brain Health, Digestive Health, Nuts and Seeds

Written by Taylor Woosley, Staff Writer. Results of the study show that after six months of daily peanut consumption participant’s polyphenol and short-chain fatty acid levels significantly increased, resulting in lower anxiety, depression, and cortisol scores, while also resulting in improvement in immediate memory.

peanutsThe relationship between the brain-gut microbiome axis has been explored, with the basis that communication exists between the nervous system, the gut, and its microbiome. Excess stress, poor diet, frequent medication use, and lack of exercise can negatively impact these bidirectional communication channels 1. Recent research suggests that components of brain functioning, and emotional behavior, are directly affected by the state of the gut microbiota 2. Diversity of the microbiome, or the myriad of microorganisms residing in the gut, consists of bacteria, viruses, fungi, etc. and this microbial community influences the inflammatory reactions and neural functioning within the brain 3. The state of the microbiota is directly affected by diet, and adequate consumption of a variety of fiber-rich foods produces short-chain fatty acids (SCFAs). These microbial metabolites act as crucial mediators between the intestinal microbiome and the immune system 4. The typical Westernized diet is highly comprised of fats and sugars, with little emphasis on proper dietary fiber intake, which directly contributes to depletion of specific beneficial bacterium and may lead to a predisposition to chronic inflammatory diseases 5. Constant exposure to microbiota-driven proinflammatory responses can affect the communication between the gut and brain, leading to a myriad of stress and anxiety disorders, depending on the state of the altered intestinal barrier 6.

In order to properly feed the diverse microbes and facilitate a symbiotic environment for the gut, researchers have explored the diverse components of nuts and legumes and their effect on the microbial ecosystem. Peanuts have been previously studied due to their global popularity as an energy-rich and nutritious legume. Peanuts offer a wide variety of phytonutrients, such as resveratrol, isoflavonoids, phenolic acids, and phytosterols, all of which help enhance overall wellness 7. Furthermore, this legume contains all the essential amino acids and is abundant in carbohydrates, lipids, proteins, vitamins, minerals, and fiber 8. The fiber components present in peanuts act as a prebiotic, or non-digestible dietary components that stimulate the growth and activity of certain beneficial microorganism 9. Offering a variety of prebiotic and polyphenol-rich foods to the gut’s microbiome strengthens the diversity of the microbes, with current research suggesting that gut microbes produce most neurotransmitters found in the brain 10.

Parilli-Moser et al conducted an experiment to further explore the link between the role the microbiome plays in relation to neurological conditions, such as stress and anxiety. In this three-arm parallel-group randomized controlled trial, 63 healthy young adults (22.71 ± 3.13 years) were placed into various groups and instructed to consume different peanut-containing products for six months.

Group 1 (SRP)25 g/day of skin roasted peanuts (n=21)
Group 2 (PB)32 g/d of peanut butter (n=23)
Group 3 (CB)32 g/d of a control butter (from peanut oil, devoid of phenolic acids and fiber) (n=19)

Compared to the CB group, those in the SRP and PB groups had higher intakes of resveratrol, p-coumaric acid (p= <0.001 for both groups), along with higher levels of m-coumaric acid (p= 0.029 and p= 0.002, respectively) at the end of the study compared to baseline.Participant inclusion criteria consisted of no history of chronic diseases, lack of peanut allergies, having a body mass index (BMI) under 25 kg/m2, and not smoking or consuming high levels of alcohol. After two weeks of no peanut consumption, participants were divided into the three groups, following their normal diet and routine, with the inclusion of the peanut product and the exclusion of other foods high in resveratrol and also nuts, due to their similar nutrition profile to peanuts. Fasting blood, along with 24-hour urine and feces, were collected at baseline and at 6 months to assess polyphenol levels, fecal short-chain fatty acids levels, along with cortisol measurements to assess stress and anxiety scores. Additionally, a food frequency questionnaire and a physical activity questionnaire was provided at baseline and at the end of the intervention to evaluate diet and physical activity. Neuropsychological tests and mood disorder questionnaires were given at baseline and at the end of the study to assess participant’s memory, executive function, and processing speed. After 6 months of daily peanut consumption, the results are as follows:

  • A significant decrease in resveratrol (p < 0.001) and p-coumaric acid intake (p= 0.016) was observed in the CB group.
  • A significant decrease in physical activity was noted in both the SRP and CB groups at the end of the study compared to baseline (p= 0.012 and p= 0.034), but no significant changes in body mass index was observed.
  • The SRP (p= 0.046) and PB (p= 0.011) groups had a significant improvement in immediate memory at the end of the study.
  • A lower anxiety score was associated with the SRP group than in the CB and PB groups compared to baseline (p< 0.001 and p= 0.016, respectively).
  • A significant decrease in the depression score was noted for all three groups, SRP, PB and CB (p= 0.007, p= 0.026 and p= 0.032, respectively) compared to baseline.
  • Cortisol levels measured in urine significantly decreased in the SRP and PB group at the end of the study compared to baseline (p= 0.004 and p= 0.008, respectively).

In conclusion, daily consumption of peanut products over the course of 6 months led to an increase in polyphenol levels in the gut, which positively affected functions of memory and stress response. Intake of peanut products with the natural fiber components intact resulted in higher concentrations of short-chain fatty acids, which were inversely related to the depression score and the urinary cortisol levels. Study limitations include the small sample size of each group, absence of a peanut-free product to serve as a control, and the lack of blinding. Further research should explore the role fiber-rich foods may have in positively altering the state of the microbiome, allowing for proper communication between the gut and the brain to occur.

Source: Parilli-Moser, Isabella, Inés Domínguez-López, Marta Trius-Soler, Magda Castellví, Beatriz Bosch, Sara Castro-Barquero, Ramón Estruch, Sara Hurtado-Barroso, and Rosa M. Lamuela-Raventós. “Consumption of peanut products improves memory and stress response in healthy adults from the ARISTOTLE study: A 6-month randomized controlled trial.” Clinical Nutrition 40, no. 11 (2021): 5556-5567.

© 2021 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Click here to read the full text study.

Posted February 24, 2022.

Taylor Woosley studied biology at Purdue University before becoming a 2016 graduate of Columbia College Chicago with a major in Writing. She currently resides in Glen Ellyn, IL.

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