Author
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Lukaski, Henry |
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Submitted to: Book Chapter
Publication Type: Book / Chapter Publication Acceptance Date: 7/26/2005 Publication Date: 3/22/2006 Citation: Lukaski, H.C. 2006. Protein turnover and mineral metabolism. In: Institute of Medicine of the National Academies, editors. Mineral Requirements for Military Personnel: Levels Needed for Cognitive and Physical Performance During Garrison Training. Washington, DC:National Academies Press. p.338-343. Interpretive Summary: Military personnel are regularly exposed to multiple stressors during training and combat. One consequence is self-imposed food restriction which can lead to significant loss of body weight and muscle mass. An unintended result is the loss of minerals associated with inadequate food intake and increased protein breakdown. This paper reviews the links between protein, and specifically muscle, breakdown and mineral excretion in urine associated with acute and chronic injury in humans. Observations in patients undergoing elective surgery indicate an increase in the urinary output of indirect markers of muscle breakdown and zinc after surgical procedures. Similarly, studies of well trained endurance athletes reveal a parallel increase in the excretion of indicators of muscle breakdown and mineral elements, specifically zinc and magnesium, in urine after strenuous exercise. The excretion of zinc in urine also increases in soldiers during intense physical training despite consumption of a diet that meets the military recommendations for zinc intake. The mechanisms linking muscle protein breakdown and increased mineral losses in urine include hormones and immune factors that stimulate breakdown of body energy reserves, such as fat and protein, and well as inhibiting accretion of protein. Food restriction also promotes the production of compounds, such as amino acids and ketones, that increase the urinary loss of minerals. Because soldiers participate in intense and prolonged training and operational activities, there is a clear need to determine mineral requirements under these conditions. This information is needed to develop dietary formulations to meet the mineral needs of active military personnel as well as civilians participating in strenuous physical activity programs. Technical Abstract: Military personnel are regularly exposed to multiple stressors during training and combat. One consequence is self-imposed food restriction which can lead to significant loss of body weight and muscle mass. An unintended result is the loss of minerals associated with inadequate food intake and increased protein breakdown. This paper reviews the links between protein, and specifically muscle, breakdown and mineral excretion in urine associated with acute and chronic injury in humans. Observations in patients undergoing elective surgery indicate an increase in the urinary output of indirect markers of muscle breakdown and zinc after surgical procedures. Similarly, studies of well trained endurance athletes reveal a parallel increase in the excretion of indicators of muscle breakdown and mineral elements, specifically zinc and magnesium, in urine after strenuous exercise. The excretion of zinc in urine also increases in soldiers during intense physical training despite consumption of a diet that meets the military recommendations for zinc intake. The mechanisms linking muscle protein breakdown and increased mineral losses in urine include hormones and immune factors that stimulate breakdown of body energy reserves, such as fat and protein, and well as inhibiting accretion of protein. Food restriction also promotes the production of compounds, such as amino acids and ketones, that increase the urinary loss of minerals. Because soldiers participate in intense and prolonged training and operational activities, there is a clear need to determine mineral requirements under these conditions. This information is needed to develop dietary formulations to meet the mineral needs of active military personnel as well as civilians participating in strenuous physical activity programs. |
