Dietary magnesium intake influences exercise capacity and hematologic parameters in rats

The effects of feeding varying concentrations of dietary Mg (50, 100, 200, or 400 ppm) for 22 days on exercise capacity and hematologic parameters were investigated in male rats. Five-week-old male Osborne-Mendel rats fed diets containing 50 or 100 ppm Mg developed transitory priapism and hyperemia, signs of Mg deficiency. Based on a treadmill test, these rats showed a markedly lower exercise endurance capacity (four hours) than rats fed the higher levels of dietary Mg (six hours). They also showed a mild macrocytic anemia. Consumption of a mineral water containing 85 ppm Mg prevented these signs of Mg deficiency. These results show that a reduction in exercise capacity can be an early effect of Mg deficiency. Hematologic changes that occurred with Mg deficiency such as macrocytic anemia may be responsible, at least in part, for the depression of exercise observed in these rats. These data are important because they illustrate the potential significance of even a marginal deprivation of dietary magnesium.