Effects of not drinking water

I normally drink 10-12 glasses a day. I had a friend tell me he heard a doctor say that we do not need that many glasses of water a day, only about 4 glasses per day. And the reason was that African-Americans are on so much medication that the water was needed to wash out the toxins that the medication produced. And, by drinking as much water as I do, I am damaging my kidney from overworking them and "washing out" the minerals needed in your body. I am an African American female, mid-forties, on no medication. What is your opinion of this?

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