Which mineral supplement is known for causing dark stools as a side effect?

The supplement associated with causing dark stools is iron. This is due to the fact that iron is often not entirely absorbed by the body, leading to unabsorbed iron passing through the digestive tract. As this unabsorbed iron is metabolized, it can react with compounds in the gastrointestinal tract and alter the color of the stool, resulting in a dark or black appearance.

This side effect is particularly common among individuals taking iron supplements, especially in higher doses, as the body processes more iron than it needs. In clinical practice, health care providers use the presence of dark stools to monitor the efficacy and potential side effects of iron supplementation, while also advising patients to be aware of this change in stool color as a typical consequence of the treatment.