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United States Department of Agriculture

Agricultural Research Service

Title: Work Inefficiency in Diet-Induced Magnesium Deficiency in Postmenopausal Women

Authors
item Lukaski, Henry
item Milne, David
item NIELSEN, FORREST

Submitted to: Federation of American Societies for Experimental Biology Conference
Publication Type: Abstract Only
Publication Acceptance Date: April 6, 1997
Publication Date: N/A

Technical Abstract: There is paucity of evidence that dietary Mg deficiency, independent of concurrent metabolic abnormalities, impacts human physiological function. We examined the effects of dietary Mg on biochemical indices of Mg status and physiological responses to submaximal exercise of 8 women, 55-70 y, who were fed conventional diets with varying Mg content: 350 mg/d for 35d (control), 150 mg/d for 93d (depletion) and 350 mg/d for 49d (repletion). Serum Mg and ultrafilterable (UF) Mg did not change. UF Mg/serum Mg increased and muscle Mg decreased (p<0.05); peak oxygen uptake (VO2), cumulative net oxygen uptake (CNVO2) and heart rate (HR) during exercise increased (p<0.05) when dietary Mg was low. Because work output for each woman was the same during each ergocycle test, the increased V02, CNV02 and HR reflect an increased physiological requirement to perform the same mechanical work when dietary Mg was low. <p>Control Depletion Repletion Serum Mg, mmol/L 0.85 +/- 0.01 0.82 +/- 0.02 0.86 +/- 0.02 UF Mg, mmol/L 0.55 +/- 0.04 0.56 +/- 0.05 0.57 +/- 0.05 % total 65 +/- 1 69 +/- 1* 65 +/- 1 Muscle Mg, mmol/g 20.1 +/- 0.6 17.7 +/- 0.5* 22.5 +/- 0.6 VO2 peak, mL/min 1118 +/- 33 1293 +/- 46* 1128 +/- 32 CNVO2, mL 5238 +/- 242 6110 +/- 247* 5319 +/- 230 HR, bpm 130 +/- 2 139 +/- 2* 128 +/- 2 Values are MEAN +/- SE, *p<0.05 These findings show that dietary Mg deficiency can be induced in apparently healthy women and that it results in energy inefficiency during controlled exercise.

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