Iron utilization in humans

Table III. Effects of Soy Protein on Iron Utilization in Humans.

The effect of various forms of phosphorus salts on zinc and iron utilization in men have not been assessed. Differences in the cecal lora growth of rats and men could result in differences between the two species in their ability to hydrolyze polyphosphates (33. 34). Thus, at this time it is difficult to speculate whether equal quantities of orthophosphates and polyphosphates in the diet would have different effects on zinc and iron utilization by human subjects. 

In humans, hemoglobin concentration and hematocrit provide information about iron utilization in erythropoiesis. These parameters, however, can be confounded by inflammation, pregnancy, dehydration, polycythemia, hemoglobinopathies, and by deficiencies of vitamin B12 or folic acid (Gibson 1990). Plasma ferritin reflects body iron stores, but is also confounded by inflammation, liver diseases, leukemia, Hodgkin s disease, or alcohol intake. Transferrin saturation and plasma transferrin receptor are valuable parameters to support the diagnosis of iron deficiency and ineffective erythropoiesis (Thorstensen and... 

In an adult human some 65% of the total iron is found in hemoglobin and myoglobin, and the bulk of the remainder is found in the storage proteins ferritin and hemosiderin. A small amount is utilized in iron enzymes at any one time. An account will be given of ferritin and the transport protein transferrin, prior to a general discussion of iron transport and storage. 

Copper is an essential element to most life forms. In humans it is the third most abundant trace element only iron and zinc are present in higher quantity. Utilization of copper usually involves a protein active site which catalyzes a critical oxidation reaction, e.g., cytochrome oxidase, amine oxidases, superoxide dismutase, ferroxidases, dopamine-/ -hydrox-ylase, and tyrosinase. Accordingly, animals exhibit unique homeostatic mechanisms for the absorption, distribution, utilization, and excretion of copper (J). Moreover, at least two potentially lethal inherited diseases of copper metabolism are known Wilson s Disease and Menkes s Kinky Hair Syndrome (I). 

Iron Utilization. Iron deficiency, a major cause of anemia in humans, is a world-wide problem (392,393,394) and the search for... 

The bioavailability of iron from any source (e.g., iron supplement, food or meal composite) is considered to be that portion of the total iron which is metabolizable. Philosophically, this concept is important because the amount of iron utilized by avian and mammalian species is directly associated with iron need. When assaying iron bioavailability, it is therefore necessary to use an organism whose need will exceed the amount provided. In animal assays of iron bioavailability, iron need is assured by a growth phase and/or creation of iron deficiency through feeding an iron deficient diet and phlebotomy. Because healthy subjects are usually used in human assays of iron bioavailability (Cook et al., 1981 Cook and Monson, 1976 Radhakrishman and Sivaprasad, 1980), it is inappropriate to compare the data obtained from animal and human assays. In fact it is questionable if assays of iron bioavailability yield good information on the quantities of metabolizable iron available when healthy human subjects are used. 

This reference dose of ferrous sulfate ascorbic acid was absorbed at a higher rate in iron deficient subjects than in iron replete subjects a ratio of the absorption of the test meal to the reference dose allowed comparisons to be made between individual subjects. As these early studies were limited to study of single food items an effort was made to extend the technique by developing designs utilizing extrinslcally tagged test meals (3,4). Utilization of these techniques has given evidence that dietary iron forms two separate pools in the gut, one a pool of heme iron and the other a pool of nonheme iron. The predominate source of iron in human diets is in the form of nonheme iron (5),... 

Binding of nutritionally important cations to dietary fiber has recently been introduced as a possible cause for poor utilization by humans of iron from diets high in vegetables and unrefined cereals. Reinhold et al. (J2) and Ismail-Beigi et al. (33) have demonstrated that the fiber component of wheat bread and bran binds iron even after the phytate has been extracted by dilute acid. In our study, the water-insoluble fraction (containing most of the neutral detergent fiber of the bran) of enzymatically dephytinized wheat bran did not inhibit, whereas... 

Reutilization of Nuclear Components. The question whether the constituents of nucleic acids may be salvaged and used again is not a simple one, and some lines of evidence do point to this possibility. Direct evidence in oral mucosa and epidermis of the rat for DNA reutilization has been presented by Outright and Bauer (CIS). This is in direct contrast to the study of Baden quoted above. In addition, studies utilizing radioactive iron injected intradermally in humans indicated reutilization of iron by epidermal cells since the half-life of the injected iron was found to be 67 days (02, 03). This is far greater than the usually... 

Elemental carbon in different shapes played a role in human life long before the term element was even coined. Charcoal and soot have been known and utilized for various purposes since -5000 BC. They were mainly obtained from wood and employed, for example, for metallurgic processes such as the production of iron. 

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