In young, apparently healthy, trained Israeli men, strenuous effort was reported to give rise to persistent magnesium (Mg) deficiency and a parallel long-term increase of cholesterol, triglycerides and blood sugar parallel 1-3. The relationship of Mg deficiency to the pathogenesis of cardiovascular disease has been increasingly documented during the last decade. Several authors have highlighted the phenomenon of sudden deaths in sport and have suggested that it is associated with cardiovascular disease. The association is discussed between Mg deficiency and increase of blood lipids and sugar, found as a sequel to strenuous effort, and cardiovascular morbidity and mortality risk reported in athletes. It is postulated that sudden death of athletes and other intensely training individuals during exertion, is mediated by the deleterious cardiovascular effects of persistent magnesium deficiency and the resultant hyperlipaemia and hyperglycaemia, which, as we have documented, follows strenuous effort.