Heavy metal contamination of food products has recently become a significant health concern. The widespread availability of dietary supplements increases the interest of health-conscious consumers in these food products. As a result, their consumption is growing worldwide due to their potential health benefits. However, dietary supplements may also contain other elements, including toxic elements, and thus affect human health. Previous studies have shown that they contain the radionuclides polonium, lead, uranium, and thorium, making them a source of internal exposure related to the decay of the isotopes studied. On this basis, the radiation safety associated with the presence of the radioactive isotopes 210Po, 210Pb, 234U, 238U, 230Th, and 232Th in calcium and magnesium supplements for adults was estimated, namely the cancer risk associated with their consumption and the risk of cancer-related death. Cancer morbidity and mortality risk ranged from 10-5 to 10-10. Cancer morbidity and mortality risk ranged from 10-5 to 10-10. The highest cancer risk morbidity and mortality was calculated for 210Po and 210Pb due to higher activities and radiotoxicity. The effect of the lower concentrations of 234U, 238U, 230Th, and 232Th in the supplements analyzed is a significantly lower risk of cancer due to their consumption and activities in the product. The study showed that both effective doses and cancer risks were low, and calcium and magnesium supplements can be considered safe for human consumption.