Berries and Steps: a protocol of a randomized, placebo-controlled pilot study testing freeze-dried blueberry powder in sedentary older adults with mild depressive symptoms.

Background: Older adults spend the majority of their day engaging in sedentary behavior, which increases risk of mortality by 22%. Despite the well-established health benefits of physical activity, a large portion of older adults remain sedentary. Recent evidence suggests that inflammation contributes to lack of motivation, which is a critical barrier to overcoming sedentary behavior in older adults. Given that inflammation is highly modifiable by diet, an anti-inflammatory dietary strategy may be a viable way to improve inflammation-driven lack of motivation and ultimately increase physical activity in sedentary older adults. However, interventions targeting such a pathway are scarce. We propose a study intervention protocol, which aims to determine the feasibility and preliminary efficacy of daily supplementation of freeze-dried blueberries. Supplementation with blueberries provides 2 anti-inflammatory nutrients (fiber and anthocyanins) to theoretically reduce inflammation-driven lack of motivation and thereby enhance physical activity in older adults with sedentary behavior and mild depressive symptoms.

Methods: The current study is planned as a single-site, randomized, double-blind, parallel pilot study in 40 older adults with sedentary behavior and mild depressive symptoms. Individuals with depressive symptoms often lack motivation and have increased levels of inflammatory cytokines, representing an ideal population for an anti-inflammatory dietary intervention to improve motivation. Participants will be randomized to consume either 48 g of freeze-dried blueberry powder (~ 600 mg of anthocyanins and ~ 8 g of fiber) or a nutritionally matched placebo powder (without any known amounts of anthocyanins and fiber) each day for a total of 12 weeks.

Discussion: Identification of a dietary intervention to target the inflammatory pathways may offer a novel and feasible approach to increase motivation and engagement of physical activity in older adults. If feasible and effective, such a strategy would help avoid the plethora of health consequences associated with sedentary behavior and physical inactivity.

Trial registration: The current study is approved by the Advarra IRB (#Pro00064749) and registered at Clinicaltrials.gov (Identifier: NCT05735587).