Last week, I had a cup of oolong tea in the evening, and I couldn’t fall asleep until 2 or 3 a.m. This experience made me wonder: how do coffee and tea affect our sleep? And what insights does the ancient Traditional Chinese Medicine (TCM) classic, “Huangdi Neijing (The Yellow Emperor’s Inner Canon)”, offer on the subject of sleep? In this blog, Songtao our TCM therapist, explores this everyday yet essential topic.
Caffeine: The Science Behind Alertness
The stimulating effects of coffee and tea primarily come from caffeine, though tea generally contains less caffeine than coffee. But how does caffeine keep us awake?
Mimicking Adenosine - Caffeine has a similar structure to adenosine, a neurotransmitter responsible for making us feel sleepy. By binding to adenosine receptors, caffeine blocks adenosine’s sedative effects, keeping us alert.
Rebound Effect - Once caffeine is metabolized, the accumulated adenosine floods the receptors, leading to a sudden wave of drowsiness.
Notably, caffeine lingers in the body for quite some time. For most adults, its half-life is about 3-4 hours, but for pregnant women or those taking certain medications, this can extend to 5-10 hours. This explains why the tea I had in the afternoon disrupted my sleep that night!
TCM Wisdom on Sleep from Huangdi Neijing
Ancient Chinese medicine has profound insights into sleep. In Huangdi Neijing, it is written:
“Wei Qi circulates in the Yang during the day and moves into the Yin at night. When Yang is depleted, one sleeps; when Yin is exhausted, one wakes”. (Lingshu - Major Confusion)
This passage describes the natural cycle of Wei Qi (defensive Qi) throughout the day: during the daytime, Wei Qi moves through the Yang channels (like the skin and muscles), while at night, it shifts to the Yin channels (internal organs). When Yang energy is drained, we feel sleepy; when Yin energy is depleted, we wake up.
Additionally, Huangdi Neijing states:
"Yin governs stillness, while Yang governs activity."
This perfectly illustrates the dynamic balance of Yin and Yang, where sleep and wakefulness follow a natural cycle of opposition, interdependence, and transformation.
The TCM View on Insomnia
From a TCM perspective, insomnia often results from an imbalance of Yin and Yang:
Excess Yang and Deficient Yin: When Yang energy is too strong, and Yin is insufficient to anchor it, the mind becomes overly active, leading to difficulty falling asleep.
Disrupted Wei Qi Flow: If Wei Qi gets stuck in the Yang meridians and fails to transition into the Yin meridians at night, sleep becomes difficult.
Tips for Better Sleep
Now that we understand how caffeine affects sleep and how TCM views sleep regulation, what can we do to improve our sleep quality?
1.Control Caffeine Intake
Limit daily caffeine consumption to under 400 mg.
Avoid caffeine after 4 p.m. (or 2 p.m. for those sensitive to it).
2. Watch Out for Hidden Caffeine Sources
Chocolate, cocoa, cola, and even some medications may contain caffeine.
Check food labels to avoid unintentional caffeine intake.
3. Create a Sleep-Friendly Environment
Avoid screens an hour before bedtime to reduce blue light exposure.
If you can’t sleep within 30 minutes, get up, do something relaxing for 20 minutes, then try again.
By managing caffeine intake, adjusting lifestyle habits, and incorporating relaxation techniques, we can all enjoy high-quality sleep. After all, a good night’s rest is not just a necessity—it’s the foundation for a productive and energetic day ahead.
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