***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Literature data on the bioavailability of various Mg forms provide scarce information on the best Mg salt to be used in animal and human supplementation . This study aim ed to investigate the bioavailability of different forms of Mg in rats using Mg stable isotopes . Eighty male Wistar rats aged 6 weeks were fed a semi-purified Mg-depleted diet for three weeks . The rats were then r and omised into ten groups and received , for two more weeks , the same diet repleted with Mg ( 550 mg Mg/kg ) as : oxide , chloride , sulphate , carbonate , acetate , pidolate , citrate , gluconate , lactate or aspartate . After 10 days of Mg-repleted diet , the rats received orally 1.8 mg of an enriched 26Mg . Faeces and urine were then collected for 4 consecutive days . Isotope ratios in faeces and urine were determined . The Mg absorption values obtained varied from 50 % to 67 % . Organic Mg salts were slightly more available than inorganic Mg salts . Mg gluconate exhibited the highest Mg bioavailability of the ten Mg salts studied . Urinary 26Mg excretion varied from 0.20 mg to 0.33 mg , and feeding with the organic pidolate , citrate , gluconate and aspartate salts result ed in higher urinary 26Mg excretion than with inorganic salts . Ultimately , 26Mg retention was higher in the rats receiving the organic salts such as gluconate , lactate and aspartate than in those receiving the inorganic salts . Taken together , these results indicate that 26Mg is sufficiently bioavailable from the ten different Mg salts studied in the present experiment , although Mg gluconate exhibited the highest bioavailability under these experimental conditions Magnesium status is a well-known modulator of the immune system . In the present study we investigated the effect of magnesium on granulocyte signalling and function . Furthermore , we performed a double-blinded r and omised study investigating the effect of a two-month magnesium supplementation period on the exercise-associated alterations in immune function . In vitro incubation of granulocytes in media of different magnesium composition result ed in significant changes in chemotactic peptide-induced calcium transients while basal calcium levels were not affected . Likewise , the stimulus-induced formation of free radicals was affected by extracellular magnesium while phagocytosis of granulocytes was not affected . In the second part of the study we investigated whether a two-month period of magnesium supplementation was able to diminish alterations in immune cell counts and functions after an exercise test until exhaustion . The magnesium status was similar in both human and placebo groups and did not change significantly after the supplementation period . Exhaustive exercise induced an activation of the immune system as indicated by an increase in granulocyte count and a post-exercise lymphopenia . In addition , chemotactic peptide-induced cellular calcium transients were enhanced post-exercise while oxidative burst and phagocytosis were decreased . These results suggest that magnesium is an important modulator of immune cell function under in vitro conditions . However , a magnesium supplementation seems to be unable to prevent any exercise-associated alterations in immune cell function in athletes with balanced magnesium status BACKGROUND Study ing magnesium pools in the body with use of stable isotopes may be helpful for evaluating magnesium status . Data on the evaluation of magnesium pools in humans are scarce . OBJECTIVE We undertook this study to evaluate the effects of a magnesium supplementation program on the size of the exchangeable body pools of magnesium and on classic indexes of magnesium status in healthy women with normal magnesium status . DESIGN Ten healthy women participated in a kinetic study with magnesium stable isotopes before and after 8 wk of magnesium supplementation . Each woman received 3 supplements containing 5.08 mmol ( 122 mg ) elemental Mg/d ( 366 mg/d ) . Before and at the end of the supplementation period , each woman received an intravenous injection of 1.67 mmol ( 40 mg ) (25)Mg , and the plasma magnesium disappearance curve was followed for the next 7 d. Two methods were used to analyze the exchangeable pools of magnesium : 1 ) formal multicompartmental modeling and 2 ) a simplified estimation of the total mass of the rapidly exchangeable magnesium pool ( EMgP ) . RESULTS In these healthy women , exchangeable magnesium pools represented 11 - 12 % of total body magnesium on the basis of multicompartmental analysis . The simplified estimation of EMgP overestimated the size of the exchangeable magnesium pools by approximately 45 - 50 % . Eight weeks of magnesium supplementation did not significantly modify the size of the exchangeable magnesium pools , whereas urinary magnesium excretion was significantly higher after 8 wk of supplementation . CONCLUSION Women with no clinical evidence of magnesium deficiency may not respond to short-term supplementation with increases in the mass of the exchangeable magnesium body pool or in magnesium turnover rates We demonstrated similar plasma concentrations and urinary losses but lower erythrocyte magnesium concentrations ( 2.18 + /- 0.04 vs 1.86 + /- 0.03 mmol/L , P less than 0.01 ) in twelve aged ( 77.8 + /- 2.1 y ) vs 25 young ( 36.1 + /- 0.4 y ) , nonobese subjects . Subsequently , aged subjects were enrolled in a double-blind , r and omized , crossover study in which placebo ( for 4 wk ) and chronic magnesium administration ( CMA ) ( 4.5 g/d for 4 wk ) were provided . At the end of each treatment period an intravenous glucose tolerance test ( 0.33 g/kg body wt ) and a euglycemic glucose clamp with simultaneous [D-3H]glucose infusion and indirect calorimetry were performed . CMA vs placebo significantly increased erythrocyte magnesium concentration and improved insulin response and action . Net increase in erythrocyte magnesium significantly and positively correlated with the decrease in erythrocyte membrane microviscosity and with the net increase in both insulin secretion and action . In aged patients , correction of a low erythrocyte magnesium concentration may allow an improvement of glucose h and ling A r and omized , placebo-controlled clinical pilot study was performed in order to examine the effect of magnesium-orotate in male idiopathic infertility . Ten males were treated daily for 90 consecutive days with 3000 mg magnesium-orotate ( Magnerot ) tablets ( Group M ) . As a control , ten other males were treated in the same way with placebo ( Group P ) . Conventional microscopic sperm characteristics ( sperm concentration , motility ratio , total number of motile sperm cells , normal morphology ratio ) , plus total and ionized magnesium levels in seminal plasma and blood serum were evaluated both prior to treatment and on day 90 , at the conclusion of the study . No significant changes in sperm characteristics , blood ionized or total Mg , or ejaculate total Mg levels were detected . However , ejaculate ionized Mg levels increased in Group M from 0.18 + /- 0.05 to 0.30 + /- 0.05 ( mmol/l ; mean + /- SD , p < 0.05 ) . Within the observation period of 3 months , one pregnancy occurred in the partner of a male from Group M. In conclusion , magnesium-orotate treatment at a dose of 3000 mg/day leads neither to a significant improvement of sperm variables nor does it increase the pregnancy rates of female partners of treated males as compared to those of controls . Thus , magnesium-orotate treatment was not shown to be effective therapy for idiopathic male infertility This study examined the effects of daily oral magnesium ( Mg ) supplementation on bone turnover  in 12 young ( 27 - 36 yr old ) healthy men . Twelve healthy men of matching age , height , and weight were recruited as the control group . The study group received orally 15 mmol Mg ( Magnosolv powder , Asta Medica ) daily in the early afternoon with 2-h fasting before and after Mg intake . Fasting blood and second void urine sample s were collected in the early morning on days 0 , 1 , 5 , 10 , 20 , and 30 , respectively . Total and ionized Mg2 + and calcium ( Ca2 + ) , and intact PTH ( iPTH ) levels were determined in blood sample s. Serum biochemical markers of bone formation ( i.e. C-terminus of type I procollagen peptide and osteocalcin ) and resorption ( i.e. type I collagen telopeptide ) and urinary Mg level adjusted for creatinine were measured . In these young males , 30 consecutive days of oral Mg supplementation had no significant effect on total circulating Mg level , but caused a significant reduction in the serum ionized Mg+ level after 5 days of intake . The Mg supplementation also significantly reduced the serum iPTH level , which did not appear to be related to changes in serum Ca2 + because the Mg intake had no significant effect on serum levels of either total or ionized Ca2 + . There was a strong positive correlation between serum iPTH and ionized Mg2 + ( r = 0.699 ; P < 0.001 ) , supporting the contention that decreased serum iPTH may be associated with the reduction in serum ionized Mg2 + .  Mg supplementation also reduced levels of both serum bone formation and resorption biochemical markers after 1 - 5 days , consistent with the premise that Mg supplementation may have a suppressive effect on bone turnover rate . Covariance analyses revealed that serum bone formation markers correlated negatively with ionized Mg2 + ( r = -0.274 for type I procollagen peptide and -0.315 for osteocalcin ) , but not with iPTH or ionized Ca2 + . Thus , the suppressive effect on bone formation may be mediated by the reduction in serum ionized Mg2 + level ( and not iPTH or ionized Ca2 + ) . In summary , this study has demonstrated for the first time that oral Mg supplementation in normal young adults caused reductions in serum levels of iPTH , ionized Mg2 + , and biochemical markers of bone turnover . In conclusion , oral Mg supplementation may suppress bone turnover in young adults . Because increased bone turnover has been implicated as a significant etiological factor for bone loss , these findings raise the interesting possibility that oral Mg supplementation may have beneficial effects in reducing bone loss associated with high bone turnover , such as age-related osteoporosis In population s , dietary intakes of potassium , calcium , and magnesium each have been inversely associated with blood pressure . However , most clinical trials in normotensive population s have not found that dietary supplements of these minerals lowered blood pressure . We tested the hypothesis that normotensive persons who have low habitual intake of these minerals would be particularly responsive to supplementation . Three hundred normotensive women in the Nurses Health Study II ( mean age , 39 years ) , whose reported intakes of potassium , calcium , and magnesium were between the 10th and 15th percentiles , received for 16 weeks ' duration daily supplements of either potassium 40 mmol , calcium 30 mmol ( 1200 mg ) , magnesium 14 mmol ( 336 mg ) , all three minerals together or placebos . At baseline , mean ( + /-SD ) 24-hour ambulatory blood pressures were 116+/-8 and 73+/-6 mm Hg systolic and diastolic , respectively , and mean dietary intakes of potassium , calcium , and magnesium were 62+/-20 mmol/d , 638+/-265 mg/d , and 239+/-79 mg/d , respectively . The mean differences ( with 95 % confidence intervals ) of the changes in systolic and diastolic blood pressures between the treatment and placebo groups were significant for potassium , -2.0 ( -3.7 to -0.3 ) and -1.7 ( -3.0 to -0.4 ) , but not for calcium , -0.6 ( -2.2 to 1.0 ) and -0.7 ( -2.0 to 0.6 ) , or for magnesium , -0.9 ( -2.6 to 0.8 ) and -0.7 ( -2.2 to 0.8 ) . The administration of calcium and magnesium with potassium did not enhance the effect of potassium alone , and the changes in blood pressure were not significant -1.3 ( -3.0 to 0.4 ) and -0.9 ( -2.2 to 0.4 ) . In conclusion , potassium , but not calcium or magnesium supplements , has a modest blood pressure-lowering effect in normotensive persons with low dietary intake . This study strengthens evidence for the importance of potassium for blood pressure regulation in the general population Electrolyte supplements may be used to prevent negative electrolyte balance during hypokinesia ( HK ) ( decreased number of kilometres per day ) . The aim of this study was to evaluate the effect of daily intakes of magnesium ( Mg ) supplements on Mg balance during prolonged HK . Studies were done during a 30–day period of pre – HK and during a 364–day period of HK . Forty male athletes aged 2 
    Output:
    
Available data analysis suggests that serum/plasma magnesium concentration , red blood cell ( RBC ) concentration and urinary magnesium excretion responded to dietary manipulation .
For other biomarkers with available data , it was not possible to draw any conclusions about their usefulness as magnesium status biomarkers .
In conclusion , although limited data were available , serum/plasma magnesium concentration , RBC magnesium concentration and urinary magnesium excretion appear to be useful biomarkers of magnesium status in the general population .