> Coffee also affects the gastrointestinal tract. It increases stomach acidity and stimulates the release of hormones that aid digestion. Both caffeinated and decaffeinated coffee promote the contractility of ileal and colonic smooth muscle, helping prevent constipation
As the two times in my adult life I've tried to make an intended break from coffee, it has ended up with almost unbearable stomach pain caused by constipation.
It's good to know that this is not linked to caffeine as I thought, so I will try un-caffinated coffee instead now because I tend to think that my general "tiredness" comes from actual caffeine.