MAGNESIO Y ATLETAS

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Effects of Magnesium Supplementation on Blood Parameters of Athletes at Rest and After Exercise VEDAT CINAR,*,1 MUSTAFA NIZAMLIOGLU,2 RASIM MOGULKOC,3 AND ABDULKERIM KASIM BALTACI3 1

High School of Physical Education and Sport, 2Department of Food Hygiene, Veterinary School, and 3Department of Physiology, Meram Medical School, Selcuk University, Karaman, Turkey Received June 21, 2006; Accepted July 18, 2006

ABSTRACT The effects of magnesium supplementation on blood parameters were studied during a period of 4 wk in adult tae-kwon-do athletes at rest and exhaustion. Thirty healthy subjects of ages ranging in age from 18 to 22 yr were included in the study. The subjects were separated into three groups, as follows: Group 1 consisted of subjects who did not train receiving 10 mg/kg/d magnesium. Group 2 included subjects equally supplemented with magnesium and exercising 90–120 min/d for 5 d/wk. Group 3 were subject to the same exercise regime but did not receive magnesium supplements. The leukocyte count (WBC) was significantly higher in groups 1 and 2 than in the subjects who did not receive any supplements (p < 0.05). There were no significant differences in the WBC of the two groups under magnesium supplementation. The erythrocyte, hemoglobin, and trombocyte levels were significantly increased in all groups (p < 0.05), but the hematocrit levels did not show any differences between the groups although they were increased after supplementation and exercise. These results suggest that magnesium supplementation positively influences the performance of training athletes by increasing erythrocyte and hemoglobin levels.

Index Entries: Blood parameters; exercise; magnesium supplement; rest; exhaustion.

*Author to whom all correspondence and reprint requests should be addressed.

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INTRODUCTION Magnesium is an important cofactor for many enzymes, required in several biochemical events and for energy metabolism (1,2). It has been suggested that there is a positive correlation between magnesium levels and physical performance (3,4).

Through high-energy diets, athletes usually receive sufficient essential minerals, including magnesium. This is not the case of subjects under a diet restricted or reduced to maintain or limit their body weight, which might be cause of insufficient magnesium intake leading to a decrease of physical performance (5,6).

In a study by Henry et al. on postmenopausal women, a direct relationship between magnesium intake and erythrocyte (RBC) and hemoglobin (Hg) levels was found (7). Abbasciano et al. stated that the red blood cell (RBC) count decreased during endurance sports (8). Baltaci et al. found higher a leukocyte count and differences in other hematological parameters in young female athletes compared to sedentary controls (9). Ozyener et al. showed that acute submaximal exercise significantly increases erythrocyte, hematocrit, (Hct), Hg, leukocyte (WBC), and trombocyte numbers in comparison to the levels before exercise and they rationalized that these increases are the result of plasma losses caused by exercise (10).

Navas and Cordovain examined the effect of magnesium supplements and training on rats and found that erythrocyte and Hg levels were higher in the trained rats receiving magnesium supplements (11).

The short-time exercise increases of WBC and other parameters might not be fully explained by the hemoconcentration mechanism theory alone.

The information available in the literature does not allow one to fully understand the effects of medium- or long-term magnesium supplementation and training on hematological parameters. This study was performed to determine how these two factors influence the red and white cells in athletes at rest and exhaustion.

MATERIALS AND METHODS Subjects Thirty healthy subjects between 18 and 22 yr of age voluntarily participated in the study. Before the start of the research protocol, all of the participants gave their consent for participation after the purpose of the study was explained to them. The participants were divided into 3 groups of 10 subjects each, kept under distinct regimes for 4 wk as follows: Group 1: sedentary subjects receiving 10 mg Mg (as magnesium sulfate) per kilogram of body weight, per day Group 2: subjects received the Mg supplement and practiced the tae-kwon- do routines for 90â&#x20AC;&#x201C;120 min/d, 5 d/wk.

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Group 3: subjects training as those in group 2 but without Mg supplements.

Fasting blood samples were drawn from all participants before and after the experimental period at rest and after exhaustion. The leukocyte, thrombocyte, and erythrocyte counts as well as other hematological parameters were measured at those occasions by standard clinical laboratory procedures.

Exhaustion Measurements To create exhaustion, the participants underwent a 20-m shuttle run test prior to blood sampling. The test was applied at the Training and Sports Academy, Selcuk University. The test starts with a slow running speed (8 km/h) at which the subject runs on a 20-m track following a signal. The subject should run to the end of the track and touch the finish line with one foot before the signal to return sounds again. The subject is allowed to continue the test if one signal is missed but is dismissed if he has difficulty in following the signal or if he or she is 3 m short of the finish line consecutively in two cycles. At this point, the running speed is increased 0.5 m/min. Every minute counts as a grade point. The result of the test is the number of accumulated points, which is taken as the indicator of endurance. The duration of the test depends on the individual’s ability and strength (12).

Measurement of Hematological Parameters Two-milliliter blood samples were drawn into EDTA tubes and used to determine the five basic hematological parameters (erythrocyte, thrombocyte and leukocyte counts, hemoglobin, and hematocrit) by means of a CELL-DYN-3500 R automatic blood analyzer at the Medical Faculty Hematology Laboratory of Selcuk University.

Statistics The statistical analysis was performed with the SPSS statistical program. The results were expressed as mean±SD. The Kruskal–Wallis analysis of variance (ANOVA) was used for comparison among groups and the Mann–Whitney U-test was applied to those with p < 0.05.

RESULTS The leukocyte counts for all study groups are shown in Table 1. No differences were noted before supplementation at rest (Rbs). At exhaustion, the WBC of all groups were higher at exhaustion, before and after supplementation (p < 0.05). Before supplementation, group 3 values were Biological Trace Element Research

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Table 1 Leukocyte Counts (Ă&#x2014; 103) at Rest and Exhaustion, Before and After Supplementation with Magnesium

Note: Rbs = resting values before supplementation; Ebs = exhaustion values before supplementation; Ras = resting values after supplementation; Eas = exhaustion values after supplementation. aValues at exhaustion higher than at rest (p < 0.05). bGroup 3 values higher than groups 1 and 2 (p < 0.05). cGroups 1 and 2 higher than group 3 (p < 0.05).

Table 2 Erythrocyte Counts (Ă&#x2014; 106) at Rest and Exhaustion, Before and After Supplementation with Magnesium

Note: All values after supplementation were higher than before supplementation. * Group 1 significantly higher, p < 0.05. ** Group 2 significantly lower, p < 0.05.

significantly higher than those of the other two groups (p < 0.05). After supplementation, the WBC of groups 1 and 2 were higher than group 3, at rest and at exhaustion (p < 0.05).

Table 2 shows the erythrocyte counts. There were no differences before supplementation. After the 4-wk supplementation period, these values significantly increased in the three study groups (p < 0.05). At rest after supplementation, the subjects in group 1 had significantly higher eryBiological Trace Element Research

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Table 3 Hemoglobin Values (g/dL) at Rest and Exhaustion, Before and After Supplementation with Magnesium

Note: No significant differences between groups, before and after supplementation. Values after supplementation significantly higher, p < 0.05.

Table 4 Hematocrit Values (%) at Rest and Exhaustion, Before and After Supplementation with Magnesium

Note: The values after supplementation increased, but not significantly.

throcyte counts than those of the exercise + supplement or exercise-only subjects. The lowest values at exhaustion after supplementation were seen in group 2.

The hemoglobin values (Table 3) were the same for all three groups, before and after supplementation with magnesium. The values after supplementation, however, were all significantly higher than those before supplementation (p < 0.05). The same trend was seen for the Hct values, although the increase after supplementation was not significant (Table 4).

Magnesium supplementation and training caused a significant increase of the thrombocyte counts in all cases (Table 5) (p < 0.05). When the three groups were compared, the values in groups 2 and 3 were significantly higher than those of group 1 (p < 0.05). The thrombocyte counts Biological Trace Element Research

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Table 5 Thrombocyte Counts (Ă&#x2014; 103) at Rest and Exhaustion, Before and After Supplementation with Magnesium

Note:* Groups 2 and 3 significantly higher than Group 1 at Ebs, Ras, and Eas, p < 0.05. Exhaustion values before and after supplementation higher than resting values, p < 0.05.

of the sedentary group increased after exhaustion, but the increase did not reach significance levels.

DISCUSSION Our results show that training and magnesium supplementation for a period of 4-wk results in increases in the number of leukocytes, erythrocytes, and thrombocytes and in the hemoglobin values, but not the hematocrit level.

The optimal performance of athletes depends on many physiological factors for which blood parameters are of importance. The type of exercise affects hematological parameters and these, in turn, influence the manner in which the athlete can handle the pressure and stress of active sports (13).

The effects of different exercise types and supplementation with various minerals on hematological parameters have been reported in several studies (5,14,15). Some studies have focused on the effects of magnesium supplementation on athletic performance and blood parameters (5,6).

Magnesium is well known as a cofactor in many enzymatic systems and participates in the energy metabolism of cells. A direct relationship between Mg level and physical performance has been established (3,4). It has been shown that magnesium deficiency results in decreased physical performance (6).

Training athletes who are on a high-energy diet usually have an adequate supply of vitamins, magnesium, and other essential minerals, but this is not so in subjects who, for whatever reason, are in a low-energy or restricted diet (5).

In the present research, it was determined how magnesium supplementation for 4 wk in sedentary and active subjects influences blood parameters, both at rest or exhaustion. The WBC count is clearly increased Biological Trace Element Research

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in all Mg-supplemented groups. At rest, the leukocyte counts of subjects that exercised but received no supplements are higher than those in groups 1 and 2, who received Mg-only and Mg + exercise regimes, respectively, but the increase is not significant. At exhaustion, the trend is reversed, with groups 1 and 2 showing higher leukocyte counts than those of group 3.

In their study, Mogulkoc et al. (16) reported that exercise increased the leucocyte levels of 11- and 12-yr-old basketball, handball, and volleyball players. The nonsignificant differences seen in our study (Table 1) correspond to adult athletes, which might be the reason for the apparent discrepancy of results. The higher leukocyte levels of sedentary and active supplemented subjects suggest that Mg might play a role in the increase.

This would be in agreement with the results of Baltaci et al. (9), who evaluated the hematological parameters of young sportswomen and compared them to controls, finding that the leukocyte counts of the active subjects were higher than in the controls. Our results also agree with those of other studies that found increased leukocyte counts after acute exercise (17,18).

The erythrocyte and hemoglobin levels of our study groups show increases after supplementation and exercise. Different results are found in the literature on how exercise affects blood parameters. In general, our results are in good agreement with those reported in the literature. No changes in RBC counts were reported in one study on marathon runners (14), whereas in another study, it was stated that endurance training increased the hemoglobin levels (13). Submaximal exercise increased the erythrocyte count and hemoglobin levels, attributing the changes to plasma losses caused by exercise (10,17,19). In a study on rats, Navas and Cordova found that magnesium supplementation in addition to training resulted in increased hemoglobin and erythrocytes (11). Henry et al. found that the hemoglobin levels and erythrocyte counts were decreased in magnesium-deficient women (7). There are studies, however, suggesting that the number of RBCs does not change with exercise (20). Abbasciano et al. reported decreased RBC counts in subjects under physical stress (8).

Finally, the nonsignificant increases of Hct found in our study are in agreement with those of Vogelaere et al. (17).

Magnesium supplementation and exercise were found to cause the thrombocyte counts to increase both at rest and exhaustion, which also seem to agree with the results of Henry et al. (7) and Navas and Cordova (11).

In summary, our results indicate that magnesium supplementation increases the leukocyte, erythrocyte, hemoglobin, and thrombocyte levels in sedentary and active subjects at rest and exhaustion.

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