(P39-17-26) Integrative Immune Phenotyping and Respiratory Outcomes After Blueberry Consumption: A Triple-Blind Randomized Controlled Trial

Objectives: Immune function changes with aging and may be influenced by chronic low-grade inflammation associated with overweight and obesity. Polyphenol-rich foods such as blueberries may modulate immune responses, but evidence from mechanistic trials is limited. We evaluated whether daily blueberry consumption modifies systemic immune biomarkers, with exploratory assessment of upper respiratory tract infection (URTI) outcomes.

Methods: This was a 12-week triple-blind, parallel-group randomized controlled trial (ClinicalTrials.gov: NCT05534893). Fifty-two adults aged 50–75 y with BMI 25–32 kg/m² were randomized (1:1) to consume freeze-dried blueberry powder or energy-matched placebo. Immune outcomes included lymphocyte phenotyping by flow cytometry, natural killer (NK) cell cytotoxicity, circulating cytokines, and cytokine production from stimulated peripheral blood mononuclear cells (PBMC). Longitudinal changes were evaluated using linear mixed-effects models. URTI symptoms were recorded prospectively using a daily symptom tracker.

Results: Fifty participants completed the intervention (placebo n=25; blueberry n=25; median age 61 y, IQR 56–67 y). No serious adverse events were reported. No statistically significant group-by-time effects were observed for lymphocyte subset distributions, NK activity, circulating cytokines, or stimulated PBMC cytokine production. Thirteen URTI episodes were recorded (blueberry n=7; placebo n=6), and the proportion of participants remaining symptom-free was similar between groups (77% vs 81%). Episodes in the blueberry group were descriptively milder and shorter in duration (2.6 SD 1.5 vs 4.0 SD 2.0 days).

Conclusions: Blueberry consumption for 12 weeks did not significantly modify systemic immune biomarkers in adults with overweight or obesity. Immune markers remained largely stable between groups over time. Exploratory observations suggested possible differences in URTI severity and duration, although the limited number of events precludes statistical inference. The integration of mechanistic immune phenotyping with clinical illness outcomes may improve understanding of dietary strategies for immune resilience.

Funding Sources: U.S. Highbush Blueberry Council