Effect of GABA-Fortified Oolong Tea on Reducing Stress in a University Student Cohort

GABA-containing tea has gained popularity as an accessible intervention to reduce the impact of chronic stress-induced autonomic imbalance and increased risk for cardiovascular disease despite a lack of evidence concerning the γ-aminobutyric acid (GABA) content in a cup of the tea and its effects on physiological and psychological stress as measures of cognitive function. We aimed to measure the effects of GABA-fortified tea consumption on heart rate variability (HRV) and stress in 30 participants using a pre-post cohort study design. Ten minute lead II ECG recordings were analyzed with Kubios software. Frequency domain parameters including total power, high and low frequency power, along with heart rate, were determined. A control group that consumed a non-fortified tea was included in the research. Statistical analysis was by two-way ANOVA for two-group comparison with time as an interaction and a significance level of p < 0.05. Oolong tea consumption led to a significant decrease in the immediate stress score and a significant improvement in HRV. We conclude that autonomic imbalance and HRV in people with acute stress is significantly reduced following a cup of GABA fortified oolong tea and highlights the complex interaction between autonomic nervous system function and mood

GABA-enriched Oolong Tea: Reducing Stress in a Student Cohort May Involve More than Just GABA

We have previously shown that the consumption of GABA-enriched oolong tea is effective in reducing stress in a student cohort. However, key constituent content has not been previously investigated, especially as applied to a standard cup of tea. Further, it has not been substantiated whether it is the suggested GABA content or other constituents that lead to these observed changes in stress behaviour. Using reverse-phase HPLC, we determined the actual content of four chemicals known to influence stress in 200 mL cups of regular or GABA-enriched oolong tea brewed to manufacturer’s instructions. We found eight times as much γ-aminobutyric acid (GABA) and 1.5 times as much caffeine in GABA-enriched oolong tea as in regular oolong tea. In contrast, there was 10 times less epigallocatechin gallate (EGCG), and half as much theanine in the GABA-enriched tea. Thus, there are changes in multiple constituents in GABA-enriched oolong tea that may contribute to the biological effects we observed in students consuming these teas