Roasted green tea is a traditional Japanese tea that is roasted over charcoal.
\nA new study suggests that drinking modest amounts of regular and roasted green tea may improve mental task performance.
\nAlthough the research has limitations, starting a daily green tea habit is worthwhile, according to experts.
\nRoasted green tea, also known as houjicha, is a type Japanese green tea roasted over charcoal to give the tea a unique smoky flavor and dark brown color.<\/p>\n
Previous researchTrusted Source has highlighted the cognitive benefits of green tea consumption, though the research has often focused on long-term effects, individual compoundsTrusted Source in isolation, or high consumption.<\/p>\n
Now, a recent study published in Scientific ReportsTrusted Source explored the potential acute impacts of roasted green tea and green tea consumption on mental task performance compared to plain water.<\/p>\n
The findings suggest that even small daily servings of green tea or roasted green tea may significantly improve task performance and mental well-being.<\/p>\n
Studying tea consumption and mental performance
\nThis study\u2019s participants included 20 healthy adult men from Japan, with an average age of 23. They were tasked with completing a 5-minute mental arithmetic task six times across two sessions in a single day.<\/p>\n
In the first session, they consumed hot water before the first three tasks and then hot water again before a rest period, totaling four water intakes.<\/p>\n
In the second session, participants either drank green tea or roasted green tea before tackling the remaining three tasks and prior to another rest period, also totaling four tea intakes.<\/p>\n
This process was repeated on a second day, 1 month later, with the type of tea being switched so that all participants experienced both teas.<\/p>\n
During these tasks, the researchers measured 11 different physiological responses to assess the impact of drinking hot water, green tea, or roasted green tea on their mental task performance.<\/p>\n
They also gathered participants\u2019 self-evaluations on fatigue, stress, mental workload, and workflow to complement their physiological data.<\/p>\n
Green tea\u2019s impact on physiological stress, mental task performance
\nCompared to drinking hot water, tea consumption during tasks resulted in significantly lower tissue blood volume (TBV), tissue blood flow (TBF), and near-infrared spectroscopy responses (NIRS) in participants.<\/p>\n
These results suggest that drinking green tea or roasted green tea may have helped moderate the participants\u2019 physiological stress responses.<\/p>\n
Aromatic compounds present in green tea, known to have relaxation effects, appeared to play a significant role in these positive outcomes.<\/p>\n
\u201cBy scrutinizing various indicators, we found that aromatic stimulation of Japanese tea beverages has the potential to induce positive effects, enhance mental task performance, promote refreshment, and alleviate feelings of fatigue,\u201d wrote the study authors.<\/p>\n
Throughout all sessions, task performance was significantly higher with tea consumption than water.<\/p>\n
However, only the roasted green tea seemed to have anti-fatigue properties despite being lower in caffeine content than regular green tea.<\/p>\n
Particularly in the sessions where roasted tea was used, a higher number of task repetitions also led to a greater improvement in response rate and task performance.<\/p>\n
Importantly, these benefits were observed with small amounts of tea and within a short time frame, which aligns with typical daily tea consumption habits.<\/p>\n
How might green tea improve mental task performance?
\nTo gain insight into the mechanisms behind this study\u2019s results, Medical News Today spoke with Alyssa Simpson, RDN, CGN, CLT, owner of Nutrition Resolution, and Eliza Whitaker, MS, RDN, a registered dietitian and medical nutrition advisor at Dietitian Insights, who were not involved in the study.<\/p>\n
Simpson explained:<\/p>\n
\u201cThe study highlights the role of aromatic stimulation from tea, particularly compounds like pyrazines in roasted green tea, in influencing mood, relaxation, and alertness by directly affecting brain activity. Additionally, tea consumption induces peripheral vasoconstrictionTrusted Source, potentially contributing to feelings of refreshment and increased alertness. \u201c<\/p>\n
\u201cThe study also suggests that aromatic stimulation activates the parasympathetic nervous system, leading to relaxation and reduced stress responses, ultimately enhancing task performance and reducing subjective feelings of fatigue,\u201d she said.<\/p>\n
Whitaker agreed, noting: \u201cWhen comparing roasted green tea and green tea, roasted green tea contains more pyrazine and aromatic components which could contribute to the mechanism behind the benefits of this study; however, further research is needed to confirm this.\u201d<\/p>\n
Long-term implications remain unclear
\nThomas M. Holland, MD, MS, physician-scientist at the RUSH Institute for Healthy Aging, Rush University System for Health, not involved in the study, clarified that despite green tea\u2019s demonstrated effect on mental task performance, \u201c[a]ssessing the overall impact on brain health in this study presents some challenges.\u201d<\/p>\n
He explained that \u201c[t]he study\u2019s demographics, including the number of participants, follow-up procedures, and age and sex distribution, are quite limited, making it difficult to generalize the findings to any other populations.\u201d<\/p>\n
Holland also expressed potential issues with study\u2019s experimental design. \u201cOne notable concern is the repetition of the mental arithmetic task six times within a single day,\u201d he told us.<\/p>\n
\u201cThis frequent repetition could potentially introduce a practice effectTrusted Source, wherein performance improves with repeated exposure to the task. Practice effects are commonly seen as a source of bias in cognitive assessments,\u201d cautioned Holland.<\/p>\n
Jane Ujoatu, DrPH, RDN, a registered dietitian and owner of Encore Nutrition and Public Health Consulting, who was not involved in the research, highlighted the need for future research to compare the effects of different teas, such as black or oolong tea, on mental tasks and to include diverse participants, those with health conditions, and women.<\/p>\n
Factors including age, diet, and lifestyle may also affect green tea\u2019s effectiveness in enhancing mental performance.<\/p>\n
Ultimately, Holland said, \u201c[f]urther research is needed to explore the long-term implications and to address potential confounding factors such as practice effects.\u201d<\/p>\n
Should you start a daily green tea habit?
\n\u201cIncorporating green tea and roasted green tea into your routine can provide numerous health benefits, but it\u2019s essential to be mindful of certain considerations,\u201d said Simpson.<\/p>\n
She recommended trying various brands and brewing methods and advises keeping it to a few cups daily to avoid any adverse effects.<\/p>\n
People on medication, particularly for high blood pressure or on blood thinners, should be careful of potential interactions, and those with kidney stone history should also be cautious of green tea\u2019s oxalate content, she said.<\/p>\n
Whitaker suggested that green tea, containing less caffeine than coffee or black tea, can be a suitable alternative for those wanting improved focus with lower caffeine intake.<\/p>\n
Regarding whether individuals should incorporate green tea, Holland concluded:<\/p>\n
\u201cConsidering that green tea is abundant in flavan-3-ols \u2014 comprising multiple catechinsTrusted Source among other flavonoids \u2014 and flavonolsTrusted Source, both of which have been linked to enhanced brain health, it is not only reasonable but also advisable to include green tea in one\u2019s diet.\u201d<\/p>\n","protected":false},"excerpt":{"rendered":"
Roasted green tea is a traditional Japanese tea that is roasted over charcoal. A new study suggests that drinking modest amounts of regular and roasted green tea may improve mental task performance. Although the research has limitations, starting a daily green tea habit is worthwhile, […]<\/p>\n
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