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

Sujatha Rajaram, Cinta Valls-Pedret, Montserrat Cofán, Joan Sabaté, Mercè Serra-Mir, Ana M Pérez-Heras, Adam Arechiga, Ricardo P Casaroli-Marano, Socorro Alforja, Aleix Sala-Vila, Mónica Doménech, Irene Roth, Tania M Freitas-Simoes, Carlos Calvo, Anna López-Illamola, Ella Haddad, Edward Bitok, Natalie Kazzi, Lynnley Huey, Joseph Fan, Emilio Ros, Sujatha Rajaram, Cinta Valls-Pedret, Montserrat Cofán, Joan Sabaté, Mercè Serra-Mir, Ana M Pérez-Heras, Adam Arechiga, Ricardo P Casaroli-Marano, Socorro Alforja, Aleix Sala-Vila, Mónica Doménech, Irene Roth, Tania M Freitas-Simoes, Carlos Calvo, Anna López-Illamola, Ella Haddad, Edward Bitok, Natalie Kazzi, Lynnley Huey, Joseph Fan, Emilio Ros

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).

Keywords: Alzheimer’s disease; age-related macular degeneration; aging; cognitive decline; dietary intervention; randomized trial; walnuts.

Figures

FIGURE 1
FIGURE 1
Design of the Walnuts and Healthy Aging (WAHA) study.
FIGURE 2
FIGURE 2
Recruitment and participant allocation.
FIGURE 3
FIGURE 3
Baseline biomarkers of adherence to walnuts and change after 1 year by intervention group. RBC, red blood cells. In red, mean and 95% CI (ANCOVA, adjusting for center, age, and sex). (A) Percentage of total fatty acids in RBC at baseline. Values are 0.233 (0.218–0.247) and 0.221 (0.206–0.236) for the walnut and control groups, respectively. (B) Percentage of change of total fatty acids in RBC after 1 year. Values are 0.163 (0.144–0.183) and 0.019 (0.001–0.039) for the walnut and control groups, respectively.

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