I read this forrum a few days ago and my grandmother has heart problems, she had to get a valve transplant about 20 years ago and still takes medicine for it. And she LOVES grapefruit, she thinks its so healthy and eats one everymorning. Shes staying with me for the week, and I saw her reaching into the fridge for a cup of grapefruit juice, she's been drinking quite a lot of it for the past week since she saw a nice big bottle at an organic food store and bought it. I told her it it could be dangerous for her because she takes medication. She's quite old too so she cant read small things, she brought me her medication and it had a tab attached to it that said not to drink grapefruit juice or eat grapefruits. After I read this to her she also admitted to have been getting really tired since shes been drinking so much of it. Just thought I'd share this fun fact :)