From the comments and my own experience, the effects of coffee drinking are more complicated than shown in this article.
By fasting for a week, and then resuming drinking a cup of coffee in the morning, I found out that if I do not drink coffee every day, I need an hour less sleep.
Now I drink it three times a week.
As an older guy, I am also concerned that it’s acidity produces prostate enlargement.
Not to mention the effects of regularly having a pastry along with the coffee.