A new study published in the journal Nutrients adds to growing evidence that what we eat can influence how we feel. Researchers at Louisiana State University found that daily blueberry supplementation might help reduce symptoms of depression and anxiety in adults living in rural communities, where access to specialized mental health care is often limited.
The 12-week, double-blind, randomized clinical trial followed 23 participants diagnosed with major depressive disorder, generalized anxiety disorder, or both, all of whom were receiving standard care. Participants consumed either a freeze-dried whole blueberry powder equivalent to one cup of fresh blueberries, or a placebo powder matched for taste, color and calories.
At multiple points during the study, participants completed standardized depression and anxiety assessments, including the Major Depression Inventory and the GAD-7 questionnaire. Clinicians also conducted diagnostic interviews using the Hamilton Depression Rating Scale. By the end of the study, those who consumed the blueberry powder showed a greater reduction in symptoms of depression and anxiety compared with those in the placebo group.
“This study suggests that something as simple as adding blueberries to the diet may have meaningful benefits for mental health, highlighting the powerful connection between nutrition and emotional well-being,” says Joseph Francis, Ph.D., the study’s lead author.
While the results are promising, the biological mechanisms behind the mood improvements are still being explored. According to Leslie Wada, senior director of nutrition and health research for the U.S. Highbush Blueberry Council/North American Blueberry Council, the findings raise important questions about how blueberries might be working in the body, even when traditional markers don’t change.
“It’s all speculation,” Wada says, noting that the researchers were not able to directly measure mechanisms in this study. “Previous research has suggested anthocyanins have an effect, but there was nothing that they were able to show from a mechanism. So based on that study, we can’t say.”
One intriguing aspect of the research is that common systemic inflammatory markers, such as C-reactive protein, did not change in the blueberry group, even though participants experienced improvements in mood. That doesn’t necessarily mean inflammation isn’t involved, Wada says.
“When you take a blood sample, it’s going all over your body, and maybe you don’t see a change,” she says. “But if you’re looking at the level of the tissue, you would be able to see it.”
Wada points to emerging research showing localized inflammation can change even when blood markers remain the same, suggesting diet-related benefits might be happening in specific tissues rather than system-wide.
Other hypotheses include the role of the gut-brain axis or the ability of blueberry compounds to directly influence brain function. In animal studies, anthocyanins — the pigments that give blueberries their deep blue color — have been shown to cross the blood-brain barrier.
“They did some studies to show that the anthocyanins cross the blood-brain barrier,” Wada says. “So is it that? Is it a combination? Usually it’s a combination.”
The study used a freeze-dried whole blueberry powder rather than fresh berries, a choice that often raises questions among consumers. Wada explains the powder is used in research to ensure consistency and accuracy, not because it is superior to fresh fruit.
“We provide the powder because we want some standardization, and it’s whole blueberries,” she says. “It’s everything, because we don’t know if it’s the anthocyanins, we don’t know if it’s the fiber. We kind of feel like it’s a combination of the two doing something synergistically.”
Freeze-drying, she added, is the gentlest processing method and helps preserve nutrients while allowing researchers to precisely measure a daily dose equivalent to one cup of fresh berries. It also makes it possible to create a true placebo, which is essential for a double-blind study.
Still, Wada says consumers don’t need supplements to see potential benefits.
“I tell the consumers, don’t go and buy freeze-dried powder off Amazon — just go to the store and buy fresh blueberries,” she says.
The study also found that the daily dose used of about one cup of blueberries is realistic for most people. “It’s a reasonable amount,” Wada says. “Some scientists have given a half-cup equivalent. If people think, ‘Oh, I can’t eat a whole cup at one time,’ have half [a cup] in the morning and half in a smoothie or something later.”
Researchers caution blueberry supplementation is not a replacement for medication or psychiatric care. However, the results suggest that dietary strategies could play a supportive role in managing mental health, particularly in underserved populations.
With its small sample size, the study is considered a pilot, but it demonstrates that rigorous nutrition research can be successfully conducted in rural clinical settings. The authors call for larger, more diverse studies to better understand how blueberries, and diet more broadly, can influence mental health outcomes.
For retailers and growers, the findings also add to the growing body of research supporting blueberries as a functional food with benefits that extend beyond physical wellness, reinforcing their role in everyday diets and long-term health.
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