Foods That Cause Dark Stools and When to Be Concerned GoodRx Chronic Constipation: a Review of Current Literature Current Gastroenterology Reports Springer Nature Link Dark stool vs black stool the difference can be serious. Dark brown stool is often food or iron related. Black, tarry stool may indicate internal bleeding and needs urgent medical attention. Understanding Poop Color Meaning: Gut Health from Your Stool Black, Green or Bloody: What's Up With My Poop? Diet vs Disease