How bad is it to drink black coffee all day?  Especially in the late afternoon and evening,  i feel like a cup of coffee really improves my mood and productivity. I'm probably drinking 5-6 cups throughout the day.  

I am doing 18:6 or 20:4 every day..... only been on this for 6 days though.  Unsure if this is a temporary adjusting period i am prolonging by drinking so much coffee or if this is a reasonable thing to be doing.  I'm also doing keto. 