Basal losses include fecal losses, urinary losses, and losses due to normal skin and miscellaneous losses. The median dietary intake is 17. Clinical effects of deficiency include impaired physical and cognitive performance. The estimate of bioavailability 18 percent is based on an assumption that 10 percent of the iron in the daily diet will come from heme iron, 25 percent of which is absorbed Hallberg and Rossander-Hulten, 1991and 90 percent will come from non-heme iron find someone write my college paper, of which approximately 17 percent is absorbed Cook et al.

In the absence of heme iron, estimates of bioavailability drop to 10 percent IOM, 2001b. As iron stores rise, there is a decrease in the percent of dietary iron that is absorbed, thus decreasing the availability of dietary iron. Iron Status and Physical Performance. The impact of adequate iron and iron supplements on maintenance and possibly enhancement of physical performance was evaluated during sports training and in endurance athletes Newhouse and Clement, 1988.

Most studies of iron were with female athletes, many of whom had evidence of iron depletion or anemia or both see Lukaski and Penland, 2004 in Appendix Hematological parameters such as hematocrit, hemoglobin, and serum iron were decreased in response to intense exercise maintained over time. Based on review of over 20 years of research on iron and athletic performance and health, Beard and Tobin 2000 concluded that reductions in hemoglobin concentration and tissue iron content can be detrimental to exercise performance, and that iron status is negatively altered in many populations of chronically exercising individuals.

Decreased hematocrit and hemoglobin impair the delivery of oxygen to the tissues and lead to a reduced VO2max. Supplementation of individuals with iron to a normal hematocrit improves VO2max Beard and Tobin, 2000 and, hence, exercise capacity and performance Woodson, 1984. Deficits of the nonheme iron that is associated with enzyme systems e. Iron-depleted, nonanemic women engaged in aerobic training were studied for six weeks with or without iron supplementation Brownlie et al.

Improvements in measures of endurance capacity with training were lower in those with tissue iron deficiency and provision of supplementary iron reversed this decrease. A subsequent placebo-controlled study from the same laboratory in similar iron-depleted, nonanemic women found that iron supplementation improved indices of progressive muscle fatigue resistance Brutsaert et al. Note that these were untrained women, which may not be analogous to what might be expected among men in assault operations.

A study of Australian soldiers consuming combat rations during operations in Australia Booth et al. Ferritin levels in those soldiers receiving only one-half the combat ration pack estimated to consume about 1,600 kcal dropped by 17 percent over the 12-day operation. However, in this paper, no conclusion was made about the consequences of the alteration in ferritin status on health or performance.

Iron Status and Mental Performance. The association of iron deficiency anemia with impaired mental performance has been noted for many years, particularly in infants and young children IOM, 2001b. Of interest to developing the assault ration are data on the use of iron supplementation to improve attention and short-term memory in adolescent girls who were iron deficient but not anemic Bruner et al.

Accuracy and attention- memory- and learning-reaction times were directly related to higher ferritin and transferrin saturation find someone write my college paper young women while, in other studies, markers of cortical activation were directly related to serum iron and ferritin levels see Lukaski and Penland, 2004 in Appendix Given the reported increased feelings of fatigue, loss of vigor, and confusion as well as decreased serum ferritin levels and dehydration when consuming restricted rations Booth et al.

Iron Status and Immune Function. Exercise affects iron requirements and metabolism Gleeson et al. Reallocation of available circulating and body iron stores occurs due to significant physical activity and resulting high energy expenditure and iron sweat losses may result in impaired immune function. Maintaining optimal resistance to infection is a complex process that involves many nutrients, including iron. Some studies have shown that infection by specific pathogenic organisms e. In addition, other studies suggest that continued use of oral or parenteral iron or the presence of excessstored iron as a result of hemochromatosis may be associated with enhanced susceptibility to infections Gleeson et al.

In individuals who are mildly iron deficient and are treated with oral iron, such as may be the case in those engaged in assault operations, data to demonstrate an adverse effect on infection rate or severity is scarce Keusch, 1999. Iron Losses Through Sweat. Studies have been conducted to estimate the amount of potential losses of iron due to sweating in hot environments and as a result of exercise. Sweat loss of whole-body iron has been estimated to be 0.

The concentration decreased with time during the exercise within the first 30 minutes of exercise and was less than that seen with sweat during heat without exercise, which also produced less sweat Waller and Haymes, 1996. Sweat iron concentration was significantly lower during the second hour. Sweat iron concentrations during the second hour were approximately 0.

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