A 3-Month Comparison of Blueberry and Date Consumption among Older Adults: Rationale, Protocol, and Initial Recruitment for a Randomized Controlled Trial (Preprint)

Abstract

Although anthocyanin-rich foods have been associated with health benefits, it is unclear how well these effects extend to older adults and common geriatric syndromes. In addition, many studies have relied upon supplements or food extracts, and the effects of whole-food supplementation remain uncertain.

To determine the effectiveness of highbush blueberry supplementation, compared with an isocaloric serving of Deglet Noor dates, on blood pressure, physical function, falls, cognition, and other domains relevant to older adults.

We are conducting a single-center randomized controlled trial among older adults residing in the greater Boston, MA region. Eligible participants include women and men aged 70 years and older. The trial was planned for conduct at a single congregate living facility for older adults, but after the COVID-19 pandemic hit, the initial recruitment was moved to an alternate senior congregate living facility and has subsequently been expanded to a second facility and the larger community. Participants are randomized on a 1:1 basis to consume 1 cup of frozen blueberries or 2-3 pitted dates daily for 3 months. Following a one-week wash-out, participants attend a fasting baseline visit that includes phlebotomy, questionnaires, functional assessments, anthropometric measurements and 24-hour electrocardiographic monitoring and ambulatory blood pressure monitoring. Participants return after 3 months for identical measurements. Recruitment was planned for 70 individuals with 15% attrition.

Recruitment for the trial began in April 2022 and ended in April 2024, when the originally planned number of completers was reached. The final population included 61 participants with a median age of 76 years (range 70-94 years), 56% women, and 53% assigned to blueberries. The demographic characteristics of enrolled participants demonstrate the tradeoffs of recruitment based in senior congregate living facilities, with unusually advanced ages but limited racial diversity and a fixed pool of potential participants.

This randomized trial will test the effectiveness of whole highbush blueberry supplementation, compared with an isocaloric serving of dates, upon physiological and clinical parameters of interest to older adults. With its emphasis on whole foods, its results will add to a growing number of studies that test the effects of anthocyanins on common chronic diseases of aging.

The trial is registered at clinicaltrials.gov (NCT05358210).