Not only strenuous but also sustained moderate physical effort causes magnesium deficiency

Serum magnesium (Mg) concentration (S-Mg), erythrocyte and mononuclear Mg content (E-Mg and M-Mg), were estimated in 35 apparently healthy male Israelis (χ age 19.2, SD 0.4) following 12 months of moderate sustained physical training and again after an 80 km march of 18 h duration (energy expenditure; ≤ 40% of VO(2max)) i.e. after strenuous effort attenuated in comparison to that studied earlier. Results: Following one pear of sustained moderate training the mean S-Mg and M-Mg were significantly decreased compared with non-trainee controls (p < 0.001). After the 80 km march, the mean S-Mg rose slightly, but statistically significantly (p < 0.001), yet still remained below the mean of the controls (p < 0.001). The mean M-Mg decreased significantly after the march (p < 0.01). There was a decrease of M-Mg in 77% of the probands; in 46% thereof down to a non-detectable level. The mononuclear cell count decreased by 75%. Conclusion: Mg deficiency (MD) is a sequel not only of strenuous effort as reported earlier, but also of attenuated strenuous effort and of prolonged sustained moderate physical training. The significant fall of the mononuclear cell count in the probands indicates impairment of immune response due to MD. Untreated MD implies, in the long-term, a potentially serious health hazard. Therefore, it is important to try to prevent the occurrence of MD in professional athletes and other exposed individuals, and if present, to treat it early.