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Enhancers and Inhibitors of Iron Absorption

Posted by Blog Monday, March 7, 2011

The iron absorbed from a meal can vary ten-fold depending on the need for iron and the enhancers and inhibitors of iron present in the meal. Adequate stomach acid is important for iron absorption. Iron is found in food in two types: Heme iron and non-heme iron.

HEME IRON
Heme iron is found only in meat, poultry, and fish. Heme iron is not found in other food; even dairy products and eggs have no heme iron. Heme iron accounts for less than 10 to 15 percent of the iron consumed, even in diets with high amounts of meat. Because heme iron is better absorbed, heme iron can account for up to 30 percent of the iron absorbed from a diet.

NON-HEME IRON
The other type of iron in food is called non-heme iron. Non-heme iron makes up about 90 percent of the iron in most diets. Non-heme iron is widely distributed in many foods; please refer to Graph 11-1. Good sources include green leafy vegetables, dried fruit, blackstrap molasses, nuts and seeds, and fortified grains. Cooking acidic food in cast iron pans can add iron to the diet. Iron supplements and iron used for food fortification are in the non-heme form. In addition, part of the iron in meat, poultry, and fish is non-heme iron.

Although it occurs in smaller amounts in the diet, heme iron is normally more easily absorbed than non-heme iron. While the absorption of non-heme iron is influenced by the other components of a meal, heme iron is much less influenced by accompanying enhancers or inhibitors. More iron is absorbed if iron stores in the body are low. Less iron is absorbed if iron stores in the body are high. The effect of body stores of iron on absorption is more pronounced with non-heme iron


Graph 11-1 Iron content of some common foods.




Figure 11-5 Enhancers and inhibitors of iron absorption.



than it is with heme iron. Several other factors can influence absorption of iron, as seen in Figure 11-5.





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