Humble tea’s antidepressant properties confirmed
A tea that’s been around for more than 900 years might be just what the doctor ordered as a treatment for depression, a new study has revealed. Already renowned for its health benefits, researchers have now demonstrated matcha tea’s antidepressant-like effects.
Matcha tea is a fine powder made from the leaves of the Camellia sinensis plant, the same plant used to produce white, green, black and oolong teas. In recent years, the health benefits of matcha tea have been touted due to its high concentration of antioxidants and anti-inflammatory substances. Matcha tea is also thought to reduce anxiety and elevate mood.
Depression is the most prevalent psychiatric disorder worldwide and can significantly impair daily functioning. In the US, one in five adults will struggle with a depressive disorder at some point in their lifetime. Although the onset varies among people, the mechanism underlying depression is thought to be caused by reduced dopaminergic function in the brain.
Dopamine is the “feel good” neurotransmitter and hormone responsible for feelings of pleasure, satisfaction, and motivation. Post-mortem examinations have shown that dopamine D1 receptor expression and function are significantly reduced in patients with major depressive disorder.
Conventional antidepressants such as selective serotonin reuptake inhibitors (SSRIs), serotonin and norepinephrine reuptake inhibitors (SNRIs) and tricyclic antidepressants can successfully treat depression by increasing dopamine, serotonin, and norepinephrine levels in the brain. Still, they have many side effects, and people can develop resistance to them.
Enter the humble matcha tea as a safe, natural alternative. Although there is plenty of anecdotal evidence that drinking matcha tea improves mood, there have been no scientific studies exploring its antidepressant properties. Researchers from Kumamoto University in Japan had previously found that Matcha tea improved anxiety levels in healthy mice by activating dopamine D1 receptors. Now, they wanted to look more closely at the effect of the tea on the brain’s circuitry.
The researchers subjected genetically modified stress-tolerant (BALB/c) and stress-susceptible (C57BL/6J) mice to social isolation. They found that giving both sets of mice matcha tea only reduced depression in the stress-susceptible mice.
“Matcha tea reduced the immobility time only in stress-susceptible mice that experienced greater stress from social isolation, and exhibited high depression-like behavior, in comparison to the stress-tolerant mice,” said Dr Yuki Kurauchi, the study’s lead author.
Immobility time is a measure of behavioral despair in mice, and increased immobility time is an indicator of depression.
Wanting to understand more, the researchers performed an immunohistochemical analysis of the brains of the mice, a way of combining anatomical, immunological, and biochemical techniques to image discrete tissue components. They found that, in stress-susceptible mice, matcha tea activated the brain’s prefrontal cortex (PFC) and the nucleus accumbens (NAc).
The PFC is the area of the brain that is most sensitive to stress, whereas the NAc plays a key role in processing rewarding stimuli. Importantly, both are crucial for controlling the brain’s dopamine levels. Activation of the PFC and the NAc causes a surge in dopamine levels, improving mood. This effect was not seen in the stress-tolerant mice. Moreover, when the stress-susceptible mice were given a dopamine D1 receptor blocker, the effects of the matcha tea were negated.
“These results suggest that matcha tea powder exerts an antidepressant-like effect by activating the dopaminergic system of the brain, and this is influenced by the mental state of the individual,” Kurauchi said.
The researchers’ findings have implications for future research and the development of new antidepressant medications. In the meantime, they recommend raising a cup of matcha tea.
“Incorporating matcha into health promotion programs has potential to improve its widespread utility,” Kurauchi said.
The study was published in the journal Nutrients.
Source: Kumamoto University