Depression is a prevalent mood disorder with a complex etiology. It is the second-most leading global cause of disability. The prevalence of a major depressive episode among adults in the United States in 2017 was more than 7%. Recent research has explored the relationship between the intake of certain nutrients and the support of mood and cognitive health in the presence or prevention of depression.

A recently published review article by Pannu and colleagues explored the potential role of flavonoids in support of mood health. Flavonoids are molecules classified as polyphenols and are found in many plants. Certain fruits, vegetables, tea, and grains contain flavonoids. Flavonoids are categorized into groups such as flavonols and flavones based on their chemical structure.

A flavone called 7,8 dihydroxyflavone (DHF) was shown in animal and laboratory studies to cross the blood-brain barrier and had relatively high bioavailability. It has also been shown to influence the nitric oxide (NO) signaling pathway and tropomyosin receptor kinase B receptors. In a laboratory study, DHF was reported to mimic and increase the hippocampal expression of brain-derived neurotrophic factor (BDNF). The BDNF is a protein that plays an important role in synaptic plasticity, nervous system modulation, memory formation, and the growth, maintenance, and survival of neurons. Altered levels of BDNF have been associated with several psychological and neurological disorders, including depression. 

Other studies have shown an increase in hippocampal BDNF levels in the presence of flavonoids. Flavonoids were also shown in animal studies to help regulate neurogenesis, synaptogenesis, neuronal plasticity, and neuronal maturation. They also influenced signaling pathways related to BDNF and helped prevent stress-induced and corticosterone-mediated decreases in BDNF expression. 

Flavonoids may also support the body’s response to oxidative stress. Oxidative stress may be linked to neuronal damage, cognitive dysfunction, inflammatory disorders, and other changes to human health. They have been shown to interfere with systems related to the production of free radicals, including NO synthase, xanthine oxidase, and inositol trisphosphate kinase. 

Classified as a flavonol, quercetin is perhaps one of the most well-known flavonoids. Particularly abundant in onions, apples, green tea, and wine, quercetin has been shown to have free radical scavenging activity. In animal studies, it was shown to modulate neuroinflammation related to microglia. It also was shown in preclinical studies to have activity related to certain neurotransmitter systems, such as monoamine oxidase enzymes. 

Flavonoids are molecules found in many fruits, vegetables, and tea. They have been shown to support the body’s response to oxidative stress. Although more research is needed to draw broader conclusions, the review article by Pannu and colleagues indicates that flavonoids may also influence certain biological processes related to mood health. 

By Colleen Ambrose, ND, MAT