Cardiff University scientists in the United Kingdom tested the potential killing effect of 33 teas on 79 bacteria. It was found that the active ingredient polyphenols in green tea had the best effect on killing superbugs, which caused intestinal diseases such as severe diarrhea. Research director Rice Berry has been engaged in tea disease resistance research since 2008. He said that a cup of green tea a day helps kill germs and prevent diarrhea. Studies have shown that green tea is more sterilized than black tea.