The aim of this work was to investigate whether Ca-alginate biopolymer beads (CaABBs) can be used to reduce the bioavailability of radionuclides in the gastrointestinal tract of humans. The uptake of strontium, uranium and thorium from a simulated gastrointestinal system was studied by in vitro techniques using CaABBs. This agent was prepared from Na-alginate through cross-linking with divalent calcium ions according to the egg-box model. The effects of process variables such as pH of the gastrointestinal juice, incubation time and solid-to-solution ratio for the removal of radionuclides from the gastrointestinal juice were investigated. The results suggest that CaABBs are a potent material for reducing the bioavailability of radionuclides with a high uptake efficiency in the gastrointestinal tract.