Walnuts, Long-Chain Polyunsaturated Fatty Acids, and Adolescent Brain Development: Protocol for the Walnuts Smart Snack Dietary Intervention Trial

Jordi Julvez, Florence Gignac, Silvia Fernández-Barrés, Dora Romaguera, Aleix Sala-Vila, Otavio T Ranzani, Cecilia Persavento, Anna Delgado, Albert Carol, Jaume Torrent, Judith Gonzalez, Eduard Roso, Jose Barrera-Gómez, Mónica López-Vicente, Raquel Garcia-Esteban, Olivier Boucher, Joan Forns, Miguel Burgaleta, Nuria Sebastián, Josefina Canals, Victoria Arija, Xavier Basagaña, Emilio Ros, Joan Vendrell, Jordi Salas-Salvadó, Jordi Sunyer, Jordi Julvez, Florence Gignac, Silvia Fernández-Barrés, Dora Romaguera, Aleix Sala-Vila, Otavio T Ranzani, Cecilia Persavento, Anna Delgado, Albert Carol, Jaume Torrent, Judith Gonzalez, Eduard Roso, Jose Barrera-Gómez, Mónica López-Vicente, Raquel Garcia-Esteban, Olivier Boucher, Joan Forns, Miguel Burgaleta, Nuria Sebastián, Josefina Canals, Victoria Arija, Xavier Basagaña, Emilio Ros, Joan Vendrell, Jordi Salas-Salvadó, Jordi Sunyer

Abstract

Background: Adolescence, when the most complex behaviors are refined to adult sophistication, represents a major window of opportunity and vulnerability for neuropsychological development. To support and protect this complex and active brain growth, different nutritional components considered essential need to be acquired from the diet. For instance, omega-3 fatty acids are mainly obtained from seafood, seeds, and walnuts. Known for their rich lipid profile, walnuts contain sizable amounts of an essential fatty acid, alpha-linolenic acid (ALA), the vegetable omega-3 fatty acid that is the precursor of two longer-chain omega-3 polyunsaturated fatty acids (omega-3 PUFA): docosahexaenoic (DHA) and eicosapentaenoic (EPA) acids. While there is growing evidence of neuropsychological improvements in the young developing brain associated with omega-3 PUFA intake, few studies have examined whether consuming walnuts during adolescence entails similar beneficial effects. There is a need to further explore the ways in which walnuts influence youthful brain function, particularly for the long-term. Thus, we designed the WALNUTs study (WSS), a population-based randomized controlled trial conducted in adolescents in Barcelona, Spain. We hypothesize that walnut intake will increase omega-3 PUFA tissue availability (particularly ALA) to a level that enhances the neuropsychological development during adolescence. Methodology/Design: We conducted a 6-month population-based randomized controlled trial in teenagers (n = 800) and we aimed to determine the effectiveness of the intervention (four walnuts per day, or 30 kernel g, ~1.5g of ALA) in enhancing brain neuropsychological and socio-emotional development compared to a control group with no walnut intervention. Before randomization, different neuropsychological tests were recorded for all participants, and blood samples (in a subsample of participants) were collected to measure omega-3 PUFA levels at baseline, and all again, after randomization and the intervention. The data is now collected and we will conduct linear regression models to assess the effect of the intervention. Discussion: The WALNUTs (WSS) study results will allow us to better understand the role of plant-based omega-3 PUFA intake from regular walnut consumption on neuropsychological development during adolescence. Results could be translated into nutritional public health recommendations targeting teenagers. Trial Registration: ClinicalTrials.gov, U.S. National Library of Medicine, National Institutes of Health # NCT02590848. Retrospectively registered 29/10/2015.

Keywords: ALA; adolescence; dietary intervention; neuropsychological development; omega-3 PUFA; randomized controlled trial; walnuts.

Conflict of interest statement

JJ, AS-V, and EmR have received grants for research through their institutions from the California Walnut Commission (CWC), Folsom, California. ER has also received honoraria for consulting and presentations from the CWC and is a nonpaid member of its Scientific Advisory Council, besides having received honoraria for presentations from Danone JS-S reports serving on the board of the International Nut and Dried Fruit Council (nonpaid member of the scientific committee) and receiving grant support from this entity through his institution. He also reports serving on the Executive Committee of the Instituto Danone Spain. He has also received research funding (walnuts, olive oil, hazelnuts, and almonds for the PREDIMED study) from the CWC; Patrimonio Comunal Olivarero, Spain; La Morella Nuts, Spain; and Borges S.A., Spain, respectively. He reports receiving consulting fees or travel expenses from Nuts for Life and the Australian Nut Industry Council. All remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflic of interest.

Copyright © 2021 Julvez, Gignac, Fernández-Barrés, Romaguera, Sala-Vila, Ranzani, Persavento, Delgado, Carol, Torrent, Gonzalez, Roso, Barrera-Gómez, López-Vicente, Garcia-Esteban, Boucher, Forns, Burgaleta, Sebastián, Canals, Arija, Basagaña, Ros, Vendrell, Salas-Salvadó and Sunyer.

Figures

Figure 1
Figure 1
Project design and structure.

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