Iron deficiency is widespread in India and is a major cause of anemia in susceptible populations, especially in those whose demand for iron is high, such as growing children or pregnant women. Many factors, including dietary components (phytates, tannins, phosphates, and high calcium intake), exercise, menstruation, and maturity may increase or reduce iron availability. Iron absorption and utilization increase as iron stores are depleted, but certain inhibiting factors in foods and beverages such as soybeans and tea can impair iron absorption. On the other hand, inclusion of meat or foods containing vitamin C in a meal enhances iron absorption. Meat also increases gastric acid secretion, which may increase iron availability and absorption.
The optimal criterion for measuring the bioavailability of iron is hemoglobin concentration in blood. Regeneration of red-blood-cell hemoglobin (an oxygen-transporting protein) can be used to measure iron bioavailability, thereby providing an easily obtained index of iron availability. Recent research also shows that interactions of other minerals, such as zinc and calcium, with iron may reduce iron bioavailability. Copper deficiency, cooked meat, and raw vegetables are considered to enhance iron absorption.