Carien M van Reekum, Claire M Williams, Martin Velichkov, Zsofia Bezur
Journal: European journal of nutrition 2024;63(4):1071-1088
PMID: 38300292
Depression encompasses a range of chronic conditions characterized by prolonged low mood and anhedonia (a loss of interest or pleasure in previously enjoyable activities). The most common forms include major depressive disorder (MDD), persistent depressive disorder (dysthymia), and seasonal affective disorder. This study aimed to investigate the acute and chronic effects of wild blueberry supplementation on mental health and cognitive function in emerging adults with depressive symptoms. The research employed a randomised, double-blind, placebo-controlled design, with both acute (2-hour) and chronic (6-week) assessments of a wild blueberry intervention. Participants were assigned in a 1:1 ratio to receive either blueberry supplementation or a placebo. Results showed a significant positive correlation between immediate improvements in mood and executive function following a single dose of blueberry supplementation—an effect not seen in the placebo group. However, in the chronic phase, both groups experienced reductions in depression symptoms, with the placebo group showing significantly greater improvements. Similar trends were observed in anxiety, anhedonia, and other depression-related outcomes. Blueberry supplementation did not significantly impact serum biomarkers of neuroplasticity [the brain’s ability to adapt and reorganise itself by forming new neural connections], inflammation, or oxidative stress [an imbalance between harmful free radicals and the body’s ability to neutralise them with antioxidants], nor did it enhance executive function over time. These findings are clinically relevant for healthcare practitioners, as they suggest that while a single dose of wild blueberries may offer short-term mood and cognitive benefits, long-term supplementation may not be superior to placebo for managing depressive symptoms.
PURPOSE
The aim of the present study was to examine the acute and chronic effects of wild blueberry supplementation on mood, executive function, and serum biomarkers of neuroplasticity, inflammation, and oxidative stress in emerging adults with moderate-to-severe depressive symptoms.
METHODS
In this double-blind trial, 60 emerging adults (M = 20.0 years, 32% male) with self-reported depressive symptoms were randomly assigned to receive a single blueberry drink (acute phase), followed by 6 weeks of daily blueberry supplementation (chronic phase), or a matched placebo drink. The primary outcome was Beck Depression Inventory-II (BDI-II) scores at 6-week follow-up. Further measures included momentary affect (PANAS-X) and accuracy on an executive function task. The data were analyzed using ANCOVAs adjusted for baseline values, sex, and habitual fruit and vegetable intake. Estimated marginal means were calculated to compare the treatment arms.
RESULTS
The blueberry drink significantly improved positive affect (p = 0.026) and executive function (p = 0.025) at 2 h post-ingestion, with change scores being positively correlated in the blueberry group (r = 0.424, p = 0.017). However, after six weeks of supplementation the reduction in BDI-II scores was greater in the placebo group by 5.8 points (95% CI: 0.8-10.7, p = 0.023). Generalized anxiety and anhedonia also decreased significantly more in the placebo group. No significant differences were found for any of the biomarkers.
CONCLUSIONS
Six weeks of wild blueberry supplementation were inferior to placebo in reducing depressive symptoms. Nevertheless, the correlated improvements in positive affect and executive function after a single dose of blueberries point to a beneficial, albeit transient, psychological effect. These contrasting results suggest a biphasic, hormetic-like response that warrants further investigation.
TRIAL REGISTRATION
NCT04647019, dated 30 November, 2020.
© 2024. The Author(s).
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