What does research say about the cultural prescription to drink 8 glasses of water each day?

The idea that you have to drink eight glasses of water a day has been shown to be a myth. Numerous studies have not shown this to be a necessity, including a 2002 study that looked at various past studies. Of course you must be properly hydrated to avoid dehydration, but there are many sources of water in what people consume. How much an individual needs to drink will depend on their personal circumstances, such as how much they exercise.