My aunt used to tell her son which is my cousin that if you drink coffee your knees will turn black.
A childhood belief about drinks

others believed things like this
- When I was little my dad told me that if you drank too much coffee it would make your skin turn black. Anon
- I used to think it was illegal for children to drink coffee— C.W.
- I always thought there was a drinking age for coffee, because it was an adult drink like beer and wine.Anon
- I used to believe that if you drank coffee before you were an adult, your skin would turn gray. Anon
- Drinking coffee before your 12 yrs, old will make the white in your eyes turn brown.— dawn b.
- if you drank coffee before your 16th birthday, your skin will turn purple.Anon