Ischaemic heart disease. An epidemiological perspective with special reference to electrolytes.

Ischaemic heart disease (IHD) is a major public health problem in most industrialised countries. In the death rates from IHD, marked differences exist between various countries and also between different areas of individual countries. Unfavourable dietary factors appear to play an important role in the aetiology of IHD, and thus differences in dietary habits and the quality of food may be mainly responsible for the geographic differences in the prevalence of IHD. The present liberal use of salt as well as the refining and other industrial processing of food increase the content of sodium and decrease the content of potassium and magnesium in the diet. The high intake of sodium and the inadequately low levels of potassium and magnesium in the diet predispose to the development of arterial hypertension. Since arterial hypertension is a major risk factor of IHD, the distorted electrolyte composition of our present diet can be considered an important aetiological factor of this disease. To decrease the body burden of sodium, diuretic agents are frequently used. Unfortunately, in the presence of the relatively low content of potassium and magnesium in the diet, the diuretic-induced increases in the excretion of these electrolytes commonly decrease the potassium and magnesium levels in the body. The falls in potassium and magnesium may increase the death rate from IHD by predisposing the heart to fatal arrhythmias, and also by other mechanisms. The likelihood of magnesium deficiency also appears to be influenced by the area of residence. The higher-than-average death rates from IHD in the so-called North Karelia area in eastern Finland and in some other areas with exceptionally high death rates from this disease may be at least partly due to the very low levels of magnesium in the soil and drinking water. It can be concluded that electrolyte disturbances have important implications in the aetiology and pathogenesis of IHD.