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Research Nut: Walnuts

Effect of a Mediterranean diet or mindfulness-based stress reduction during pregnancy on child neurodevelopment: A prespecified analysis of the IMPACT BCN Randomized Clinical Trial.

Crovetto, F., A. Nakaki, A. Arranz, R. Borras, K. Vellvé, C. Paules, M.L. Boutet, S. Castro-Barquero, T. Freitas, R. Casas, A. Martín-Asuero, T. Oller Guzmán, I. Morilla, A. Martínez-Àran, A. Camacho, M. Pasqual, M. Izquierdo Renau, Ó. J. Pozo, A. Gomez-Gomez, R. Estruch, E. Vieta, F. Crispi, E. Gratacós, 2023. Effect of a Mediterranean diet or mindfulness-based stress reduction during pregnancy on child neurodevelopment: A prespecified analysis of the IMPACT BCN Randomized Clinical Trial. JAMA Network Open, 6(8), e2330255. https://doi.org/10.1001/jamanetworkopen.2023.30255

Importance: Maternal suboptimal nutrition and high stress levels are associated with adverse fetal and childhood neurodevelopment. Objective: To test the hypothesis that structured interventions based on a Mediterranean diet or mindfulness-based stress reduction (MBSR) during pregnancy improve child neurodevelopment at age 2 years. Design, setting, and participants: This was a prespecified analysis of the parallel-group Improving Mothers for a Better Prenatal Care Trial Barcelona (IMPACT BCN) randomized clinical trial, which was conducted at a university hospital in Barcelona, Spain, from February 2017 to March 2020. A total of 1221 singleton pregnancies (19 to 23 weeks’ gestation) with high risk of delivering newborns who were small for gestational age were randomly allocated into 3 groups: a Mediterranean diet intervention, an MBSR program, or usual care. A postnatal evaluation with the Bayley Scales of Infant and Toddler Development, 3rd Edition (Bayley-III), was performed. Data were analyzed from July to November 2022. Interventions: Participants in the Mediterranean diet group received monthly individual and group educational sessions and free provision of extra virgin olive oil and walnuts. Those in the stress reduction group underwent an 8-week MBSR program adapted for pregnancy. Individuals in the usual care group received pregnancy care per institutional protocols. Main outcomes and measures: Neurodevelopment in children was assessed by Bayley-III at 24 months of corrected postnatal age. Results: A total of 626 children (293 [46.8%] female and 333 [53.2%] male) participated at a mean (SD) age of 24.8 (2.9) months. No differences were observed in the baseline characteristics between intervention groups. Compared with children from the usual care group, children in the Mediterranean diet group had higher scores in the cognitive domain (β, 5.02; 95% CI, 1.52-8.53; P = .005) and social-emotional domain (β, 5.15; 95% CI, 1.18-9.12; P = .01), whereas children from the stress reduction group had higher scores in the social-emotional domain (β, 4.75; 95% CI, 0.54-8.85; P = .02). Conclusions and relevance: In this prespecified analysis of a randomized clinical trial, maternal structured lifestyle interventions during pregnancy based on a Mediterranean diet or MBSR significantly improved child neurodevelopmental outcomes at age 2 years.

Key Area: Cognitive Health

A walnut-enriched diet for 2 years changes the serum oxylipin profile in healthy older persons.

Cofán, M., A. Checa, M. Serra-Mir, I. Roth, C. Valls-Pedret, A. Lopez-Illamola, M. Doménech, S. Rajaram, I. Lázaro, J. Sabaté, E. Ros, C.E. Wheelock, A. Sala-Vila, 2023. A walnut-enriched diet for 2 years changes the serum oxylipin profile in healthy older persons. J Nutr. S0022-3166(23)72794-6. https://doi.org/10.1016/j.tjnut.2023.12.007.

Background: Oxylipins are products derived from polyunsaturated fatty acids (PUFAs) that play a role in cardiovascular disease and aging. Fish oil-derived n-3 PUFAs promote the formation of anti-inflammatory and vasodilatory oxylipins; however, there are little data on oxylipins derived from α-linolenic acid (C18:3n-3), the primary plant-derived n-3 PUFA. Walnuts are a source of C18:3n-3.Objectives: To investigate the effect on serum oxylipins of a diet enriched with walnuts at 15% energy (30-60 g/d; 2.6-5.2 g C18:3n-3/d) for 2 y compared to a control diet (abstention from walnuts) in healthy older males and females (63-79 y). Methods: The red blood cell proportion of α-linolenic acid was determined by gas chromatography as a measure of compliance. Ultra-performance liquid chromatography-tandem mass spectrometry was used to measure serum concentrations of 53 oxylipins in participants randomly assigned to receive the walnut diet (n = 64) or the control diet (n = 51). Two-year concentration changes (final minus baseline) were log-transformed (base log-10) and standardized (mean-centered and divided by the standard deviation of each variable). Volcano plots were then generated (fold change ≥1.5; false discovery rate ≤0.1). For each oxylipin delta surviving multiple testing, we further assessed between-intervention group differences by analysis of covariance adjusting for age, sex, BMI, and the baseline concentration of the oxylipin. Results: The 2-y change in red blood cell C18:3n-3 in the walnut group was significantly higher than that in the control group (P < 0.001). Compared to the control diet, the walnut diet resulted in statistically significantly greater increases in 3 C18:3n-3-derived oxylipins (9-HOTrE, 13-HOTrE, and 12,13-EpODE) and in the C20:5n-3 derived 14,15-diHETE, and greater reductions of the C20:4n-6-derived 5-HETE, 19-HETE, and 5,6-diHETrE. Conclusions: Long-term walnut consumption changes the serum oxylipin profile in healthy older persons. Our results add novel mechanistic evidence on the cardioprotective effects of walnuts.

Key Area: Heart Health

Effect of walnut supplementation on dietary polyphenol intake and urinary polyphenol excretion in the Walnuts and Healthy Aging Study.

Amen, R.I., R. Sirirat, K. Oda, S. Rajaram, I. Nwachukwu, M. Cofan, E. Ros, J. Sabate, E.H. Haddad, 2023. Effect of walnut supplementation on dietary polyphenol intake and urinary polyphenol excretion in the Walnuts and Healthy Aging Study. Nutrients.15(5):1253. https://doi.org/10.3390/nu15051253.

Among all tree nuts, walnuts contain the highest total polyphenols by weight. This secondary data analysis examined the effect of daily walnut supplementation on the total dietary polyphenols and subclasses and the urinary excretion of total polyphenols in a free-living elderly population. In this 2-year prospective, randomized intervention trial (ID NCT01634841), the dietary polyphenol intake of participants who added walnuts daily to their diets at 15% of daily energy were compared to those in the control group that consumed a walnut-free diet. Dietary polyphenols and subclasses were estimated from 24 h dietary recalls. Phenolic estimates were derived from Phenol-Explorer database version 3.6. Participants in the walnut group compared to the control group had a higher intake of total polyphenols, flavonoids, flavanols, and phenolic acids in mg/d (IQR): 2480 (1955, 3145) vs. 1897 (1369, 2496); 56 (42,84) vs. 29 (15, 54); 174 (90, 298) vs. 140 (61, 277); and 368 (246, 569) vs. 242 (89, 398), respectively. There was a significant inverse association between dietary flavonoid intake and urine polyphenol excretion; less urinary excretion may imply that some of the polyphenols were eliminated via the gut. Nuts had a significant contribution to the total polyphenols in the diet, suggesting that a single food like walnuts added to habitual diet can increase the polyphenol intake in a Western population.

Walnut protein: A rising source of high-quality protein and its updated comprehensive review.

Wen, C., Z. Zhang, L. Cao, G. Liu, L. Liang, X. Liu, J. Zhang, Y. Li, X. Yang, S. Li, J. Ren, X. Xu, 2023. Walnut protein: A rising source of high-quality protein and its updated comprehensive review. J Agric Food Chem. 71(28):10525-10542.

Recently, plant protein as a necessary nutrient source for human beings, a common ingredient of traditional processed food, and an important element of new functional food has gained prominence due to the increasing demand for healthy food. Walnut protein (WP) is obtained from walnut kernels and walnut oil-pressing waste and has better nutritional, functional, and essential amino acids in comparison with other vegetable and grain proteins. WP can be conveniently obtained by various extraction techniques, including alkali-soluble acid precipitation, salting-out, and ultrasonic-assisted extraction, among others. The functional properties of WP can be modified for desired purposes by using some novel methods, including free radical oxidation, enzymatic modification, high hydrostatic pressure, etc. Moreover, walnut peptides play an important biological role both in vitro and in vivo. The main activities of the walnut peptides are antihypertensive, antioxidant, learning improvement, and anticancer, among others. Furthermore, WP could be applied in the development of functional foods or dietary supplements, such as delivery systems and food additives, among others. This review summarizes recent knowledge on the nutritional, functional, and bioactive peptide aspects of WP and possible future products, providing a theoretical reference for the utilization and development of oil crop waste.