Author
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Finley, John |
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Submitted to: The American Journal of Clinical Nutrition
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 1/4/1999 Publication Date: N/A Citation: N/A Interpretive Summary: Manganese is a nutrient that is essential and one that can be extremely toxic. Deficiency of manganese causes great problems in domestic animals and manganese toxicity is an important problem in many human miners and ore smelters. However, relatively little is known about how the human body absorbs manganese and maintains a relatively constant body content (homeostasis) control of the element. It is well known that iron in the diet interferes with absorption of manganese, but it is not known if iron stores in the body affect the absorption and retention of manganese from the diet. This study has shown convincing evidence that healthy young women that differ only in the amount of iron stores in the body have great differences in the absorption and retention of manganese. Low iron stores resulted in greatly increased absorption of manganese, but manganese excretion was correspondingly enhanced. This resulted in the body controlling the retention of manganese remarkably well over a wide range o intakes. These results show that whether concern is for a potential deficiency or toxicity of manganese in humans, the amount of iron stores in the body, as well as the amount of iron in the diet, is a factor that must be carefully considered. Technical Abstract: The purpose of this study was to determine if Fe stores affect Mn absorption. Twenty-seven healthy young women with serum ferritin concentrations above 50 or less than 15 mg/dL participated in the study. Subjects consumed, in a crossover design, diets supplying either 0.7 or 9.5 mg Mn/d for 60 days. Mn absorption, retention and balance were assessed the last 30d of each dietary period by using an oral dose of 54Mn. Dietar Mn did not alter blood measures of Mn or trace element status, but subjects with high serum ferritin concentrations exhibited depressed arginase activity. There was a significant interaction between ferritin status and dietary Mn on 54Mn absorption. Absorption of 54Mn was greatest in subjects with low ferritin who consumed diets low in Mn, and absorption was least in the subjects with high ferritins who consumed diets high in Mn. Biological half-life of 54Mn was significantly longer in subjects fed low Mn and in subjects with high serum ferritin status. Manganese balance was only affected by the amount of Mn in the diet. Serum ferritin concentrations were associated with many measures of Mn metabolism, with the association depending on ferritin status and/or dietary Mn intake of the subject. These results demonstrate that Fe status is a primary factor determining the amount of Mn absorbed from a meal by young women. When greater amounts of Mn are absorbed, the body compensates by eliminating the absorbed Mn at a faster rate. |
