Food, iron enrichment

There is a possibility that some milk constituents regulate the absorption of ions in the intestine. In studying manganese metabolism we turned to the low iron content in milk. Iron has received great attention in pediatric nutrition. The concern has been to prevent the anemia caused by iron deficiency earlier often found in childhood. Wide milk consumption by infants and young children makes this food an attractive vehicle for iron fortification. Iron-enriched proprietary milk substitutes can adequately prevent the anemia common to infants who subsist largely on low-iron mother s or cow s milk (53). 

Dietary iron level does not seem to affect the efficiency with which dietary iron is converted into hemoglobin when ferrous sulfate (Table 1) or when ferric orthophosphate (Table 2) is the primary source of dietary iron. This is also true for white bread (Table 2) however, the source of the iron in the enriched flour used in the bread is unknown. That the efficiency of converting food iron into hemoglobin is not affected by dietary iron concentration is important to bioavailability testing because it is often difficult to formulate diets with precise amounts of iron, especially when foods are the sources of iron. 

Iron enrichment of food is becoming more and more usual. To sifted flour 65 mg iron per kg meal is added. The enrichment material may heferrum reductum, a fine dispersed, porous, metaUic iron. A different type of bonded iron, which is more easily absorbed by the body, is also used. 

Dangers of Therapeutic Administration of Iron Good Food Sources of Iron Factors Affecting the Utilization of Iron in Foods Enrichment and Fortification of Foods with Iron Enrichment Fortification... 

By the beginning of World War II, cereal companies had started to enrich their products with thiamin, riboflavin, niacin, and iron. Enrichment means the restoration of some of the nutrients that are removed during the processing of a food. Later, in about 1955, fortification of cereals was started. Fortification means the addition of certain nutrients to foods in order to provide higher levels of such nutrients than are normally present in the natural, unprocessed foods. 

About 20% of the iron in the average U.S. diet comes from fortified products. Enrichment of flour (bread) and cereals with iron (along with thiamin, riboflavin, niacin, and with calcium enrichment optional), which was initiated in 1941, has been of special significance in improving the dietary level of iron in the United States. It is noteworthy that the major iron-enriched foods provide the following quantities of iron ... 

The enrichment program followed in the United States is (/) the enrichment of flour, bread, and degerminated and white rice using thiamin [59-43-8] C 2H y N O S, riboflavin [83-88-5] C2yH2QN4Na02P, niacin [59-67-6] CgH N02, and iron [7439-89-6]-, (2) the retention or restoration of thiamin, riboflavin, niacin, and iron in processed food cereals (J) the addition of vitamin D [67-97-0] to milk, fluid skimmed milk, and nonfat dry milk (4) the addition of vitamin A [68-26-8], C2qH2qO, to margarine, fluid skimmed milk, and nonfat dry milk (5) the addition of iodine [7553-56-2] to table salt and (6) the addition of fluoride [16984-48-8] to areas in which the water supply has a low fluoride content (74). 

World Health Organization. 1977. Enrichment of dried skim milk. Food Nutr. 3, 2-7. Zemel, M. B., Soullier, B. A. and Steinhardt, N. J. 1982. Effects of calcium, ortho- and polyphosphates on calcium, zinc, iron, and copper bioavailability in man. Fed. Proc. 42, 397. 

Auclair, J. C. 1995. Implications of increased UV-B induced photoreduction Iron(II) enrichment stimulated picocyanobacterial growth and the microbial food web in clear-water acidic Canadian Shield lakes. Canadian Journal of Fisheries and Aquatic Sciences 52 1782—1788. Auclair, J. C., P. Brassard, and P. Couture. 1985. Total dissolved phosphorus Effects of two molecular weight fractions on phosphorus cycling in natural phytoplankton communities. Water Research 19 1447—1453. 

Water-soluble bioaotives may also be protected from their environment by entrapment within a matrix (e.g., gel) or the use of lipid coats. Most research on delivery of water-soluble bioactives has been on systems for enriching foods with water-soluble vitamins and minerals and more recently on the use of bioactive peptides in food. The delivery of bioavailable iron has been of particular interest because of the widespread problem of iron deficiency. 

Precision The precision of the absorption value depends upon tfe precision of P, and E measurements This method for isotopic enrichment measurements by mass spectrometry has a precision of 2% as does the measurement of F by atomic absorption This precision is adequate for absorption and bioavailability studies with zinc and copper (Table I) since zinc and copper absorption are in the range of 30-70% Only fairly large changes in iron absorption can be discerned because non-heme iron absorption is typically less than 10% This may not be a serious problem in bioavailability studies since it is doubtful that very small changes in iron absorption from single foods are biologically significant ... 

A common misnomer used on food products and even in the press is antioxidant minerals. Let s debunk this term now. Minerals themselves do not actually have antioxidant capacity but rather become attached to enzymes that do. In this role, the mineral is called a cofactor, which means that it allows an enzyme or protein to perform antioxidant work. Among the most frequently mentioned minerals in this category is selenium, which enables the peptide glutathione—the main antioxidant made in our bodies—to act as an antioxidant. Manganese, magnesium, iron, zinc, and copper are other dietary minerals having roles with enzymes involved in antioxidant functions. Many superfruits are particularly enriched with these minerals. 

This chapter mentions some iron chemistry Important to its bioavailability and the changes which may be induced by food processing. The reader may refer to the chapter by Spiro and Saltman (1) for a discussion of inorganic iron chemistry. This author has critically reviewed the iron sources used for food enrichment earlier (2). A good review of the chemistry of iron in myoglobin has been published by Livingston and Brown (3). Forth and Rummel (4) have made available an extensive review on iron absorption and factors which affect iron absorption. 

It is sometimes the practice in the food industry to add the most bioavallable iron salt at the last practical processing step, with the hope of maintaining iron bloavallability with no sacrifice in product quality. For example, ferrous sulfate is sometimes used at the bakery level for enriching flour during dough formulation. It is not added to the flour at the mill because ferrous sulfate is a prooxidant and can cause rancidity and off flavors (7). The less reactive and more flour compatible iron phosphates are sometimes avoided, based upon research which show the iron phosphates are not bioavallable. The preference for one iron source over another stems from their relative ranking in terms of biological values, as shown in Table II. 

Table II. Iron sources currently used In food enrichment and their relative biological values (RBV) based upon direct feeding.

An extensive series of studies performed at the FDA Division of Nutrition established a wide range of bioavailabilities for the iron sources used in food enrichment (8-12). However, the rank in Table 11 was based on direct feeding of the iron source to test animals. The impact of food processing or of the food matrix on iron bioavailability is not apparent in these rankings. Large differences in bioavailability between iron sources will become smaller or change completely as a result of some types of processing, while other processes have little effect. 

Effect of Heat Processing on Bioavailability of Added Iron. Several studies in Table III measured directly the effect of heat processing on added iron. These studies compared processed foods to a control group of identical unprocessed food. Studies in Table 111 utilizing unprocessed controls include 15, 19, and 23. Other studies did not employ an unprocessed control, but used a reference dose to enable comparisons from study to study. Reference doses of ferrous sulfate (most animal assays) or ferrous ascorbate (most human tests) were frequently used. Preparation of ferrous ascorbate, usually a 2 1 molar ascorbic acid iron solution, has been detailed by Layrisse et al. (25). These controls enabled measurement of variation in iron absorption from subject to subject, important in view of greater absorption of an iron deficient versus an iron replete subject. When a reference dose was fed as a radiolabeled salt (55Fe), and on alternate times the test diet was fed with a different radiolabel (59Fe), errors due to variation in subject absorption were eliminated, as each subject served as its own control. The different availabilities of various iron sources from baked enriched rolls were established in this manner (17). 

Anemia results from insufficient oxygen supply, often because of a decrease in hemoglobin (Hb) blood levels. Approximately 65 to 70 percent of total body iron resides in Hb. In the U.S., many foods, especially those derived from flour, are enriched in iron. In third-world countries, however, scarcity of dietary iron is a major contributor to anemia. This information illustrates one important fact about disease that results from metal deficiency, namely, the need for an adequate supply of essential metals in food. A related aspect, one of greater interest for bioinorganic chemistry, is the requirement that metals be adequately absorbed by cells, appropriately stored, and ultimately inserted into the proper environment to carry out the requisite biological function. For iron, these tasks. 

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