Tea remains a staple in many British households, with approximately 100 million cups consumed daily across the UK. Recent research highlights tea’s potential to significantly reduce the body’s primary stress hormone, cortisol, provided it is enjoyed before 4pm.
Mike Kocsis, founder and hormone health specialist at Balance My Hormones, explains the dual role tea plays in managing stress and sleep hormones. “Cortisol, the stress hormone, should naturally decline as the day progresses, while melatonin, the sleep hormone, increases in the evening. Tea influences both: its plant compounds can help reduce cortisol, but its caffeine content may inhibit melatonin production,” he says.
A randomised double-blind trial conducted at University College London involved men consuming four cups of black tea daily for six weeks, while a control group drank a placebo with matched caffeine content. Following a stressful task, cortisol levels in tea drinkers fell by 47% within 50 minutes, compared to a 27% reduction in the placebo group. Additionally, those who drank tea reported feeling more relaxed.
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The study’s design, which controlled for caffeine levels, indicates that compounds specific to tea, such as L-theanine and flavonoids, rather than caffeine alone, contribute to improved cortisol recovery.
However, the timing of tea consumption is crucial. A typical mug of black tea contains around 40 to 50 milligrams of caffeine-roughly half that of a standard coffee. While a single cup might seem modest, drinking multiple cups in the afternoon can accumulate enough caffeine to disrupt sleep.
Research published in Science Translational Medicine found that caffeine intake equivalent to a double espresso three hours before bedtime delayed the body’s melatonin rhythm by approximately 40 minutes. This delay affects the internal biological clock, not merely the sensation of feeling alert.
Furthermore, a separate sleep study demonstrated that consuming 400 milligrams of caffeine-even six hours before bed-reduced total sleep time by over an hour. Although this dose is much higher than that found in tea, it illustrates why afternoon caffeine consumption can interfere with restful sleep.
To balance the benefits of tea against its potential sleep disruption, Kocsis recommends making the last caffeinated cup before 4pm for those retiring around 10.30pm or 11pm. This ensures at least six hours between caffeine intake and bedtime. Earlier consumption in the morning and early afternoon still provides the calming effects associated with tea’s unique compounds.
After 4pm, switching to decaffeinated teas, which generally retain beneficial L-theanine and flavonoids, or caffeine-free herbal infusions is advisable.
Caffeine sensitivity varies individually due to factors such as age, genetics and medication, so some people may require an earlier cut-off, while others might tolerate later consumption without sleep issues. Starting with a 4pm limit is practical, with adjustments made based on personal sleep quality.
Kocsis emphasises that while tea can contribute to a calmer evening, it is not a substitute for medical treatment. Persistent issues with sleep, energy or mood lasting several months warrant professional hormone testing rather than self-experimentation with tea habits.