Iron is the essential nutrient that helps produce red blood cells and transport oxygen throughout the body. It is a key component of hemoglobin, the protein inside red blood cells that binds oxygen in the lungs and carries it to tissues. Iron is also part of myoglobin, which helps supply oxygen to muscles.
The body obtains iron from foods such as red meat, poultry, seafood, beans, lentils, tofu, spinach, and fortified grains. Heme iron from animal foods is generally absorbed more efficiently than non-heme iron from plants. Vitamin C can improve absorption of non-heme iron, which is why vegetables, beans, or cereal are often paired with fruit or another vitamin-C-rich food.
Too little iron can lead to iron-deficiency anemia, causing fatigue, weakness, pale skin, shortness of breath, or difficulty concentrating. However, more is not always better: excessive iron can be harmful, and supplements should be used with medical guidance. Calcium, vitamin C, and vitamin D are important nutrients, but they do not perform iron’s specific role in hemoglobin.