I actually have real life - if anecdotal - experience to answer this. I cut to decaf from a 3 large cups a day habit of black coffee over a year ago. My produc

I actually have real life - if anecdotal - experience to answer this. I cut to decaf from a 3 large cups a day habit of black coffee over a year ago. My productivity has actually gone up. I am mainly attributing this to the reduction in anxiety and how it has allowed my mind to slow down and better focus. I find that I am better able to keep on tasks and manage my to do lists. I was a heavy coffee drinker under the same assumption that I could not function without it or would be slow, plus I love the taste. Turns out regular exercise and good sleep have far more impact on my productivity.