This randomized, double-blind, placebo-controlled clinical trial evaluates whether 70 days of daily cranberry juice consumption improves cognitive performance and motor accuracy and reduces psychological and physiological stress responses during a motor-cognitive dual-task multitasking challenge in healthy adults aged 30-55 (Aim 1). It is hypothesized that chronic cranberry juice intake will enhance dual-task performance and attenuate stress reactivity (Hypothesis 1). It is further hypothesized that cranberry juice will mitigate multitasking-related fatigue, mood fluctuations, and cognitive impairment, accompanied by favorable changes in circulating stress biomarkers and stress-regulatory neurochemical pathways (Aim 2/Hypothesis 2). Finally, the study incorporates gut analysis to determine whether cranberry juice induces beneficial shifts in the gut microbiota and microbial metabolites (e.g., SCFAs) and whether these changes are associated with improved cognitive and stress-related outcomes, consistent with a microbiome-gut-brain axis mechanism (Aim 3/Hypothesis 3).
At least 110 pounds
Between 30 and 55 years
BMI between 18.9 and 29.9 kg/m²
A minimum education level of high school or above
Heavy caffeine users (consuming more than 300 mg/day or more than two cups of coffee per day)
Alcohol consumption exceeding three drinks per week
A smoking history of 10 years or more, or current use of cannabis products
Uncontrolled hypertension
Parallel
Cranberry juice
Other interventionParticipants will consume the cranberry juice beverage by mouth each day for 70 days following a run-in period.
Placebo juice
Other interventionParticipants will consume the placebo cranberry juice beverage by mouth each day for 70 days following a run-in period.
Cognitive task performance (serial subtraction accuracy)
Total number of correct subtractions during the multitasking cognitive task Measure Description: Counting backward aloud from a random number between 800-999 by 3, 7, and 17; performance scored as total correct subtractions across the task.
Cognitive task performance (serial subtraction errors)
Outcome Measure: Total number of incorrect subtractions during the multitasking cognitive task Measure Description: Same serial subtraction task; performance scored as total incorrect subtractions.
Mood
Change from baseline to end of intervention in mood assessed using the Visual Analog Mood Scale (VAMS). The VAMS is a self-report visual analog measure of current mood states collected during study visits per protocol.
State anxiety
Change from baseline to end of intervention in state anxiety assessed using the State-Trait Anxiety Inventory - State Subscale (STAI-State). The STAI-State is a self-report measure assessing state anxiety in response to multitasking stress collected during study visits per protocol.
Mental fatigue
Change from baseline to end of intervention in mental fatigue assessed using the Mental Fatigue Scale (MFS). The MFS is a self-reported questionnaire evaluating perceived mental fatigue and related cognitive symptoms. Scores will be collected during study visits and analyzed per protocol to assess changes following cranberry juice intervention.
Sleep quality
Change from baseline to end of intervention in sleep quality assessed using the Leeds Sleep Evaluation Questionnaire (LSEQ). The LSEQ is a self-report questionnaire evaluating subjective sleep quality and related dimensions of sleep and awakening, collected during study visits per protocol.
Gut microbiome composition and diversity
Change from baseline to end of intervention in gut microbiome composition and diversity assessed from stool samples.
Short-chain fatty acids (SCFAs)
Change from baseline to end of intervention in fecal concentrations of acetic acid, propionic acid, and butyric acid assessed from stool samples.
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