The aim of this research was to determine the interdependence between calcium and magnesium in drinking water, and the morbidity from ischemic heart disease (IHD). A structured epidemiological questionnaire was used to collect information on the amount of drinking water consumed by 200 respondents in areas with the highest and lowest values of Ca and Mg. In addition, information on various risk factors for IHD (smoking, physical activity) was assembled for the same population group. In order to determine the average daily intake of Mg and Ca among the respondents, we ran a semi-quantitative questionnaire on frequency of food intake over the course of the previous year. The correlation between risk factors was assessed using linear regression and Pearson’s coefficient of linear correlation. Finally, ROC analysis was employed to determine the minimal protective values for Mg and Ca. Despite the daily intake of drinking water in the respondents averaging less than 2l, a negative correlation between Ca and Mg from drinking water and risk factors for IHD were still observed. The analysis concluded that from the standpoint of preventing IHD, it would be necessary to have a daily intake of Ca and Mg of at least 75 mg Ca and 7 mg of Mg consumed through drinking water.