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Absorption of dietary iron in iron salt form (as in most supplements) varies somewhat according to the body's need for iron, and is usually between 10% and 20% of iron intake. Absorption of iron from animal products, and some plant products, is in the form of heme iron, and is more efficient, allowing absorption of from 15% to 35% of intake.
A later study found that erythorbic acid is a potent enhancer of nonheme-iron absorption. [5] Since the U.S. Food and Drug Administration banned the use of sulfites as a preservative in foods intended to be eaten fresh (such as salad bar ingredients), the use of erythorbic acid as a food preservative has increased.
Some non-heme iron proteins contain one Fe at their active sites, others have pairs of Fe centers: Many mono-Fe proteins are alpha-ketoglutarate-dependent hydroxylases . Major examples are the lipoxygenases , isopenicillin N synthase , protocatechuate 3,4-dioxygenase , deacetoxycephalosporin-C synthase , [ 1 ] and aromatic amino acid hydroxylases .
The same can occur with elements in food, such as calcium, which impacts both heme and non-heme iron absorption. [39] Absorption of iron is better at a low pH (i.e. an acidic environment), and absorption is decreased if there is a simultaneous intake of antacids. Many other substances decrease the rate of non-heme iron absorption.
Iron-binding proteins are carrier proteins and metalloproteins that are important in iron metabolism [1] and the immune response. [2] [3] Iron is required for life.Iron-dependent enzymes catalyze a variety of biochemical reactions and can be divided into three broad classes depending on the structure of their active site: non-heme mono-iron, non-heme diiron , or heme centers. [4]
[11] [12] The absorption of heme iron is 2–3 times faster than non-heme iron. [13] After absorption, the iron from preparation becomes part of the iron pool in the body. Upon stimulation, the reduction of iron storage Fe3+ in the enterocyte to Fe2+ ferroportin allows the passage of iron through the cell membrane for export.
It is recommended for vegans to daily eat iron-rich foods in combination with vitamin C, because vitamin C enhances iron absorption. [107] [108] Due to the low absorption rate on non-heme iron, it is recommended to eat dark leafy greens (and other sources of iron) together with sources of vitamin C. [109]
Phytoplankton can, however, obtain iron from siderophore complexes by the aid of membrane-bound reductases [42] and certainly from iron(II) generated via photochemical decomposition of iron(III) siderophores. Thus a large proportion of iron (possibly all iron) absorbed by phytoplankton is dependent on bacterial siderophore production.
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