The study, performed by researchers from the University of Reading, UK, looked at the effect of the blueberry beverage in 50 children and 21 young people, and assessed mood using the Positive and Negative Affect Schedule.
Data showed a significant improvement in so-called positive affect (PA), but not negative affect (NA).
“Although preliminary, these results are intriguing and warrant focused investigation of the relationship between flavonoids and mood, as well as with mental health more generally,” wrote the researchers in Nutrients.
“The distinctive effect of flavonoids on PA but not NA is notable,” they added. “PA and NA reflect orthogonal facets of mood. A low PA is more highly linked to depression, and high NA is more closely related to anxiety. Thus, these data suggest that the effect of flavonoid consumption on mood may be specific to depressive disorders, rather than pervasive across different mood states.”
Commenting on the potential biological plausibility of the observations, the researchers proposed two mechanism(s) of action: The first involves a potential indirect effect on blood flow in the brain, which would enhance executive functioning, and “thus helping to inhibit cognitive features (i.e., rumination) that maintain depression”.
The second involves the direct inhibition of the enzyme monoamine oxidase (MAO) by blueberry anthocyanins. “MAO is involved in the oxidation of monoamines, some of which are neurotransmitters involved in the regulation of mood (e.g., serotonin, dopamine, and noradrenaline),” they explained. “MAO inhibitors have been used to treat mood disorders. Thus, the consumption of fruits high in flavonoids, such as blackcurrants, may significantly reduce MAO activity, thereby increasing circulating monoamines, and elevating mood.”
The researchers concluded: “Given the potential implications of these findings for preventing depression, a disabling and common mental health problem in adolescents and adults, it is important to replicate the study and assess the potential to translate these findings to practical, cost-effective and acceptable interventions.”
Blueberries & working memory vs placebo
Another recently published study also added to the potential cognitive effects of blueberries, with scientists from Exeter University in England reporting that blueberry concentrate may increase activity in select regions of the brain, and boost working memory in older adults (approximately 68 years of age).
Writing in Applied Physiology, Nutrition, and Metabolism, the scientists report that 30 ml of blueberry concentrate per day (providing 387 mg anthocyanidins) for 12 weeks were associated with “significant increases in brain activity […] in response to blueberry supplementation relative to the placebo”.
The data also showed that that working memory improved in the blueberry group, versus placebo.
“Supplementation with an anthocyanin rich blueberry concentrate improved brain perfusion and activation in brain areas associated with cognitive function in healthy older adults,” they concluded.
These findings support those reported in a 2010 study led by Robert Krikorian from the University of Cincinnati Academic Health Center, which found that a daily drink of about 500 mL of blueberry juice was associated with improved learning and word list recall, as well as a suggestion of reduced depressive symptoms in older people with early memory problems (Journal of Agricultural and Food Chemistry, Vol. 58, No. 7, pp 3996–4000).
2017, 9(2), 158; doi:10.3390/nu9020158
“Effects of Acute Blueberry Flavonoids on Mood in Children and Young Adults”
Authors: S. Khalid et al.
Applied Physiology, Nutrition, and Metabolism
Published online ahead of print, doi: 10.1139/apnm-2016-0550
“Enhanced task related brain activation and resting perfusion in healthy older adults after chronic blueberry supplementation”
Authors: J.L. Bowtell et al.