Define Iron Factors affecting absorption of dietary iron?

We have read earlier that iron in foods occurs either as haem or non-haem iron. Haem iron comprises of iron in combination with porphyrins and is found only in the flesh foods in the form of haemoglobin and myoglobin. Muscle meats are therefore good sources of haem iron. Haem iron is absorbed to a much greater extent than non-haem. Haem iron absorption is generally 2- 3-fold higher than non-haem iron absorption. The average absorption of haem iron from meat-containing meals is about 25%.

The absorption of haem iron can vary from about 40% during iron deficiency to about 10% during iron repletion. Haem iron can be degraded and converted to non-haem iron if foods are cooked at a high temperature for too long. Iron absorption is not affected by other dietary factors except calcium which has been shown to depress haem iron absorption. In addition to providing higher bio available iron, haem iron compounds also enhance non-haem iron absorption. Further, non-haem iron absorption in healthy adults may vary from less than 1% to about 0% depending on the composition of the diet.