Study adds to case for natural alternative for depression
Effects of Acute Blueberry Flavonoids on Mood in Children and Young Adults
Major depressive disorder is the leading international cause of disability and is estimated to affect 350 million people worldwide. It is the second most common cause of death in 15–29 years old, via suicide.
Current treatments for depression include psychological therapies and a range of pharmacological agents. The treatment options recommended for children and adolescents are limited, with only one recommended pharmacological treatment, fluoxetine, in addition to psychotherapy.
These treatment options are further constrained because of concerns about the use of anti-depressant medication with young people and because most young people do not have easy access to psychological therapies.
Therefore, there is a pressing need for alternative interventions, especially those that offer a cost-effective and practical means of preventing, or alleviating, depression in this population.
A common symptom of depression is impaired cognitive functioning, with significant deficits in executive functioning (EF). EF is an umbrella term, describing cognitive processes such as working memory, planning, problem-solving, cognitive flexibility, inhibitory control, directing attention, thoughts and, therefore, behaviours.
Impaired EF is believed to maintain depressive symptoms, such as negative self-perception and low mood, via perseveration and rumination. Importantly, EF is associated with the development of the frontal area of the brain, an area that continues to mature and develop throughout adolescence and into early adulthood. Thus, any disturbance to the development of the frontal region during this critical period (for example because of an episode of depression) can have a long-lasting impact and may explain why depression that occurs during adolescence and early adulthood is associated with long-term impairments into adult life.
Flavonoids are a class of polyphenols (micronutrients) found naturally in fruits, vegetables, tea, coffee and cocoa. Flavonoid consumption has been associated with both vascular and cognitive benefits across the lifespan.
Single-dose flavonoid interventions have produced improvements in attention, inhibition, visuospatial memory and executive function between 2–6 h post-consumption, whilst supplementation of flavonoids for 1.5–8 weeks has been associated with improved visuospatial memory and improved long-term memory.
Numerous mechanisms of action have been investigated to explain the beneficial effects of flavonoids on cognition. These include increases in cerebral blood flow, protecting against neuronal stress via anti-inflammatory and anti-oxidative effects and positively stimulating neural signaling pathways, such as Extracellular Signal-Regulated Kinase (ERK), Serine/Threonine-specific Protein Kinase (Akt) and Brain-Derived Neurotrophic Factor (BDNF), leading to improved neural signaling.
Independently of the experimental evidence that shows flavonoids improve cognitive performance, there is emerging evidence that flavonoids may also support mental health and well-being.
Epidemiological data shows that lifetime consumption of fruit and vegetables (and therefore higher flavonoid consumption) predicts a lower incidence of depression in later life. The benefits are also seen earlier in life; a recent systematic review concluded that whilst the quality of evidence was weak, there was a consistent body of research reporting cross-sectional and longitudinal associations between nutrition and mental health in children and young people.
Similar findings have been shown by other authors. However, there is an absence of studies exploring the effects of flavonoid-rich interventions on mood.
Given the well-documented links between flavonoid consumption and cognition, and between cognition and depression, the studies reported in this paper assess the acute effects of flavonoid-rich wild blueberries (WBB) on mood two hours post-consumption. This two-hour interval coincides with the time-frame for the peak absorption and metabolism of the anthocyanins present in blueberries.
In addition, it is important to establish whether acute effects on mood are observable prior to considering a chronic flavonoid-based intervention for mood outcomes.
Two independent groups, healthy children and young adults, were recruited. These groups represent individuals who are at crucial stages of mental and cognitive development and thus plausible points at which prevention and public health interventions may be particularly powerful.
This study demonstrated acute effects of blueberry flavonoid consumption on Positive Affect and no effect on Negative Affect in healthy children and young adults.
Dietary interventions could play a key role in promoting positive mood and are a possible way to prevent dysphoria and depression.
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.
We are grateful to the Wild Blueberry Association of North America who provided the freeze-dried wild blueberry powder used for this study.