Iron is vital for the formation of hemoglobin and red blood cells, which transport oxygen throughout the body, but it has no direct effect on digestion or gut function. In fact, high doses of iron — especially from supplements — can lead to constipation, nausea, and digestive upset in some people. Iron is essential for energy and oxygen delivery, but it doesn’t assist in regulating bowel movements or maintaining a healthy gut microbiome. While it’s important to meet your iron needs, especially to prevent anemia, fiber remains the go-to nutrient for digestive and gut health support.