Select Committee on GRAS Substances (SCOGS) Opinion: Iron - Report on Bioavailability and Utilization of Iron
Iron -Report on Bioavailability and Utilization of Iron
- SCOGS-Report Number: PB 224 122/AS*
- Type Of Conclusion: There is no conclusion type.
- ID Code: 7439-89-6
- Year: 1973
- 21 CFR Section: There is no CFR citation.
LSRO RESUME: It is apparent that in the United States the iron enrich ment of foods is accomplished almost entirely through the use of four compounds: ferrous sulfate, reduced iron (so-called), ferric orthophosphate, and sodium iron pyrophosphate. In the regulation establishing the original flour and bread enrichment program, the iron to be added was described only as "harmless and assimilable." Considering the assay values which have been determined for either ferric orthophosphate or sodium iron pyrophosphate, it would be difficult to interpret "assimilable" in a manner which would include either compound. The former has a value of 25 to 30 percent that of ferrous sulfate; the latter a value of 5 to 10 percent. It seems obvious that, from the point of view of the consumer, the addition of ferric orthophosphate to a cereal food is a very minor nutritional benefit, and the addition of sodium iron pyrophosphate is essentially futile. Therefore, it would seem wise to examine each present use of these salts in the hope that an iron compound of greater bioavailablity might be substituted. Some of our consultants were firmly of the opinion that fullest use was not being made of ferrous sulfate at the present time; particularly so at the bakery level. The Iron Committee has stated that "the use of ferrous sulfate at the bakery level appears to create no problems," but, for reasons of convenience or reluctance to change, other forms of iron are still used. The belief was expressed that if allenrichment of bread and other baked goods were carried out at the bakery this would promote a greater use of ferrous sulfate. As noted in Table 2 when enrichment is done at the flour mill the iron added is preponderantly reduced iron. A development of great potential for extending the use of ferrous sulfate in the enrichment program would be the commercial availability of a stabilized form of this salt. The objective is to treat the compound in some manner so that its untoward effects on flour or other food during storage is inhibited while its good absorption from the digestive tract is retained. The problem is under active investigation and there is reason to believe that it will be solved in some degree. The most important iron source in the enrichment of foods is, by present estimates of use, reduced iron. In an addendum to this report (Appendix A), Patrick has provided valuable and much-needed information on the seveal iron powders which are collectively referred to as "reduced iron" in the food industry. He describes the process by which each is manufactured and suggests how this may influence the presence of impurities, particle size distribution, and biological activity. It is obvious that the extent to which the particles of iron dissolve in the acid of the stomach must be a very important determinant of bioavailability, but it is indicated that not only the size of the particle but also its shape, surface area and density influence the speed with which it dissolves. The differences in the latter properties are suggested in the illustrations. The possible effect of the method of manufacture on the biological properties of iron powders would suggest that distinctive names should be applied to each. The Food Chemicals Codex (1972) contains monographs of "Iron, Electrolytic" and "Iron, Reduced" but none on iron prepared by the carbonyl method. This could indicated that no carbonyl iron owder is used in the enrichment of foods in this country, but because of the present imprecise designation, "reduced iron," this assumption might be wrong. This situation should be clarified.
The excellent absorption of iron reduced by hydrogen observed by Cook et al (1973) in human subjects was ascribed, in large part, to the very small particles achived in milling the small radiolabeled sample. These authors reported that more than 95 percent of the particles ranged in size from 5-10 microns, which they acknowledged was smaller than is commercially available. Even though it would be unrealistic economically, and, according to Patrick, perhaps hazardous to attempt the commercial production of such extremely fine iron powders, efforts in this direction should be considered. Certainly, in the use of iron powders for food enrichment, average particle size distributin must be an important specification. Cook et al. (1973) have listed the size distribution in the better commercial products.
In Appendix B certain comments and suggestions have been made in the hope of expediting the development of an official assay method for assessing the bioavailability of the iron in different sources. There is urgent need for an official well-designed assay. Without it there is little hope that the widely divergent values, that have been reported on the same products, can be resolved, or that further progress can be made in solving the remaining problems of the enrichment program.