Anyone who likes to keep their teeth pearly and white with teeth whitening may have had their plans thwarted if they have ever drunk black tea.
Doctors Michael Roizen and Mehmet Oz told the Idaho Stateman that the tannin in the drink can stain smiles because it clings to tooth enamel.
To prevent this, they recommended swirling some water around in the mouth after every cup of black tea to rinse away the tannin, or brushing thoroughly.
"Floss daily to remove plaque, which acts like a stain magnet, darkening teeth around the edges," they also said.
For people who already have staining, Dr Roizen and Dr Oz said it may be a good idea to speak to a dentist about teeth whitening treatments.
Although black tea may not be good for teeth, recent research from the University of Rochester suggested that wine and cranberries may be, as they contain substances that fight bacteria which could otherwise lead to decay.