Health fads that will kill us

How many times do we have conflicting "solid scientific evidence" and then after some time, "evidence to the contrary"? The number of times that scientists make sweeping statements and retract them and reissue them is stupendous.

Here are some of those. 

1) A normal human being requires eight glasses of water a day. 

2) Vitamin supplements improve a hundred million things. 

3) A glass of wine prevents heart disease. 

4) Dark chocolate is good for you. 

5) Three cups of tea prevents strokes.