Final answer:
Iron deficiency is responsible for 50% of anemia cases worldwide, often resulting from inadequate dietary intake, issues with iron absorption and transport, or chronic bleeding.
Step-by-step explanation:
The cause that accounts for 50% of anemia cases worldwide is a) Iron deficiency. Iron deficiency anemia is highly prevalent among certain populations including children, adolescent girls, and nursing mothers. It is characterized by a low hemoglobin content in the blood, typically 5 to 9 g/100 ml. This deficiency can occur due to insufficient dietary iron intake and is common in teens, children, vegans, and vegetarians. Conditions that impair iron absorption and transport, as well as slow, chronic bleeding, can also lead to iron deficiency anemia. It occurs when the amount of available iron is insufficient to allow production of sufficient heme. This can be caused by a deficiency of iron in the diet, slow, chronic bleeding, or an inability to absorb and transport iron.