Vitamin C from food or from supplements is the strongest enhancer of iron absorption. The presence of vitamin C in a meal can increase the amount of non-heme iron that is absorbed. Ameal with 25 mg of vitamin C can double the iron absorbed.
A meal with 50 mg of vitamin C can increase non-heme iron absorption up to six times as much as a meal without vitamin C. Vitamin C changes the ferric iron (Fe3+) in food into ferrous iron (Fe2+). The vitamin C in the food becomes chelated with the iron in an iron ascorbate form that is very absorbable. However, vitamin C does not help with the absorption of iron from iron supplements.
THREE OTHER ENHANCERS OF IRON ABSORPTION
There are three other enhancers of iron absorption. The mechanisms of action and the amount of the increases in absorption of these enhancers are not known at present. First, the presence of heme iron acts as an enhancer of non-heme iron absorption. Second, fermented foods such as sauerkraut and fermented soy sauce can enhance the absorption of iron from a meal. Third, several food acids, such as citric acid, increase iron absorption.
INHIBITORS OF IRON ABSORPTION
The strongest inhibitors of non-heme iron absorption are phytates, also known as phytic acid. Phytates are found in legumes and whole grains. Small amounts of phytates can reduce iron absorption by half. In addition to containing phytates, soybeans have an independent factor that reduces the bioavailability of iron. Legumes, however, are rich in iron and can provide a useful amount of iron in a diet despite lower bioavailability. Foods containing vitamin C, such as green vegetables, are an especially useful addition to a meal with legumes or grains because of the ability of vitamin C to increase iron absorption.
Certain foods, such as raw spinach, contain oxalates that can bind some of their iron, making it unavailable for absorption. Certain polyphenols inhibit the bioavailability of iron. Many polyphenols such as flavonoids do not inhibit iron absorption. Only the polyphenols with gallic acid, which are often found in tannins, have been found to interfere with iron absorption. Iron absorption can be reduced by drinking beverages with tannic acid, such as wine, tea, or coffee during or within two hours of a meal. Spices such as oregano can also reduce iron absorption. Vitamin C greatly reduces the inhibiting effects of oxalates and tannins. Since many of the vegetables with oxalates also contain large amounts of vitamin C, this may compensate for the iron-inhibiting effects of the oxalates.
A meal with 50 mg of vitamin C can increase non-heme iron absorption up to six times as much as a meal without vitamin C. Vitamin C changes the ferric iron (Fe3+) in food into ferrous iron (Fe2+). The vitamin C in the food becomes chelated with the iron in an iron ascorbate form that is very absorbable. However, vitamin C does not help with the absorption of iron from iron supplements.
THREE OTHER ENHANCERS OF IRON ABSORPTION
There are three other enhancers of iron absorption. The mechanisms of action and the amount of the increases in absorption of these enhancers are not known at present. First, the presence of heme iron acts as an enhancer of non-heme iron absorption. Second, fermented foods such as sauerkraut and fermented soy sauce can enhance the absorption of iron from a meal. Third, several food acids, such as citric acid, increase iron absorption.
INHIBITORS OF IRON ABSORPTION
The strongest inhibitors of non-heme iron absorption are phytates, also known as phytic acid. Phytates are found in legumes and whole grains. Small amounts of phytates can reduce iron absorption by half. In addition to containing phytates, soybeans have an independent factor that reduces the bioavailability of iron. Legumes, however, are rich in iron and can provide a useful amount of iron in a diet despite lower bioavailability. Foods containing vitamin C, such as green vegetables, are an especially useful addition to a meal with legumes or grains because of the ability of vitamin C to increase iron absorption.
Certain foods, such as raw spinach, contain oxalates that can bind some of their iron, making it unavailable for absorption. Certain polyphenols inhibit the bioavailability of iron. Many polyphenols such as flavonoids do not inhibit iron absorption. Only the polyphenols with gallic acid, which are often found in tannins, have been found to interfere with iron absorption. Iron absorption can be reduced by drinking beverages with tannic acid, such as wine, tea, or coffee during or within two hours of a meal. Spices such as oregano can also reduce iron absorption. Vitamin C greatly reduces the inhibiting effects of oxalates and tannins. Since many of the vegetables with oxalates also contain large amounts of vitamin C, this may compensate for the iron-inhibiting effects of the oxalates.
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