I didn't know why at first, drinking green tea made my stomach uncomfortable. Later, I learned that green tea is raw tea. It is not suitable for people who have a cold stomach. In order to drink tea regularly, I looked at it on the internet and I learned that black tea, Puer cooked tea and Tieguanyin are all cooked tea, may be suitable for me to drink. Now I drink three brands of tea, one is Keemum Blak Tea, the other is Dayi Puer (raw), plus Bama Tieguanyin. It is hard to say which one is better, as long as after drinking them my stomach doesn't feel sick. For me, they are all good tea.