"Although coffee strongly stimulates the flow of Qi, which is helpful for any type of stagnation, unfortunately it does not regulate its flow. This is like the herb Chai Hu (for those of you who understand Chinese herbal medicine). Due to the fact that it stimulates the flow of Qi so strongly, yet does not regulate it, the stimulation of flow can actually damage the Liver Yin as the movement is too strong. When talking about the herb Chai Hu, this is why it is often used alongside certain other herbs, such as Bai Shao, which helps to negate these side effects.
When the Liver Yin becomes damaged it creates Heat, which leads to two perpetuating issues. Firstly, the Heat from the Liver rises to agitate the Heart Fires – essentially throwing more Wood onto the Fire. Secondly, when the Liver Yin is damaged, it draws upon the Kidney Yin for support. This causes the Kidney Yin to deplete, the Qi to rise (again agitating the Heart), and results in a lack of Kidney Yin to restrain the Heart Fire. Once this happens, palpitations may begin to occur when drinking coffee, lower back pain can arise, and Liver type tinnitus can occur. It should be noted that decaf coffee is not an answer to this either, as it is the coffee bean that holds these properties, and not the caffeine itself. Also, certain methods of decaffeination are damaging in their own ways!"
Rob Aspell