90Sr (t1/2 = 29.1 y) is one of the most important nuclear fission elements. After the nuclear power plant disasters of Chernobyl and Fukushima Daiichi, 90Sr was released into the atmosphere and the ocean. 90Sr is harmful to humans because it has a long half-life, and its daughter radionuclide, 90Y (t1/2 = 64.1 h), emits high-energy beta particles. It has been reported that internal exposure to 90Sr could be associated with the development of leukemia and osteosarcoma. Therefore, compounds inhibiting the absorption of radiostrontium from the gastrointestinal tract into the bloodstream and enhancing its elimination after intake can decrease the absorbed radiation dose of people exposed to radiostrontium. Indeed, basic research has shown that alginate can promote the excretion of 90Sr.