Iron is stored up to three years in men, but only one year in females. Also, females have monthly menstruation, which puts them at risk of iron deficiency.
Plant-based diets are structured around plants that contain a non-heme form of iron that difficult to absorb in the body. Leafy greens and vegetable contain oxalic acid and tannic acid which bind to iron and prevent its absorption.
People that donate blood regularly are at risk of developing iron deficiency. Because it decreases the total red blood cells, which reduces the iron levels in blood.
Because infants and children experience a growth surge, so the body requirements for all the elements and minerals increase. This growth surge put infant and children under the risk of developing iron deficiency.