The Walnuts and Healthy Aging Study (WAHA): Protocol for a Nutritional Intervention Trial with Walnuts on Brain Aging

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Sujatha Rajaram1†, Cinta Valls-Pedret2,3†, Montserrat Cofán2,3, Joan Sabaté1, Mercè Serra-Mir2,3, Ana M. Pérez-Heras2,3, Adam Arechiga4, Ricardo P. Casaroli-Marano5, Socorro Alforja5, Aleix Sala-Vila2,3, Mónica Doménech2,3, Irene Roth2,3, Tania M. Freitas-Simoes2, Carlos Calvo2,3, Anna López-Illamola2,3, Ella Haddad1, Edward Bitok1, Natalie Kazzi1, Lynnley Huey1, Joseph Fan6 and Emilio Ros2,3*

1 Center for Nutrition, Healthy Lifestyle and Disease Prevention, School of Public Health, Loma Linda University, Loma Linda, CA, USA, 2 Lipid Clinic, Endocrinology and Nutrition Service, Hospital Clínic, Institut d’Investigacions Biomèdiques August Pi i Sunyer, Barcelona, Spain, 3 Centro de Investigación Biomédica en Red Fisiopatología de la Obesidad y Nutrición, Instituto de Salud Carlos III, Madrid, Spain, 4 Department of Psychology, School of Behavioral Health, Loma Linda University, Loma Linda, CA, USA, 5 Ophthalmology Service, Hospital Clínic, Institut d’Investigacions Biomèdiques August Pi i Sunyer, Barcelona, Spain, 6 Department of Ophthalmology, School of Medicine, Loma Linda University, Loma Linda, CA, USA

Abstract

Introduction:

An unwanted consequence of population aging is the growing number of elderly at risk of neurodegenerative disorders, including dementia and macular degeneration. As nutritional and behavioral changes can delay disease progression, we designed the Walnuts and Healthy Aging (WAHA) study, a two-center, randomized, 2- year clinical trial conducted in free-living, cognitively healthy elderly men and women. Our interest in exploring the role of walnuts in maintaining cognitive and retinal health is based on extensive evidence supporting their cardio-protective and vascular health effects, which are linked to bioactive components, such as n-3 fatty acids and polyphenols.

Methods:

The primary aim of WAHA is to examine the effects of ingesting walnuts daily for 2 years on cognitive function and retinal health, assessed with a battery of neuropsychological tests and optical coherence tomography, respectively. All participants followed their habitual diet, adding walnuts at 15% of energy (_30– 60 g/day) (walnut group) or abstaining from walnuts (control group). Secondary outcomes include changes in adiposity, blood pressure, and serum and urinary biomarkers in all participants and brain magnetic resonance imaging in a subset.

Results:

From May 2012 to May 2014, 708 participants (mean age 69 years, 68% women) were randomized. The study ended in May 2016 with a 90% retention rate.

Discussion:

The results of WAHA might provide high-level evidence of the benefit of regular walnut consumption in delaying the onset of age-related cognitive impairment and retinal pathology. The findings should translate into public health policy and sound recommendations to the general population (ClinicalTrials.gov identifier NCT01634841).