Successful Aging: How to address and verify what's a 'miracle cure' claim

Q Although active, my father at age 83 has a number of chronic conditions. Among them are painful knees and urinary incontinence. He believes both can be fixed or cured and continues to respond to newspaper ads that claim to be the answer. How can I convince him that most of these are hoaxes? He just cannot accept the fact he is getting older.