Reduction in the Absorption of Dietary Strontium in Man by Nutritional Factors

Radioactive isotopes of strontium, mainly Sr, may considerably contribute to the total activity of long-lived fission products released into the environment in nuclear accidents. Consequently, the ingestion of strontium radionuclides with contaminated foodstuffs may result in a significant internal radiation exposure of members of the public. The committed radiation dose dependents significantly on the fraction of the ingested activity that crossed the gut wall (f1 value). In controlled tracer kinetic investigations, the influence of black and green tea on the gastrointestinal uptake of strontium was investigated, since tannin, a constituent of tea, is well known for being an inhibitor of gut uptake of some trace metals. In further experiments, the effect of sodium alginate and pectin, which are naturally occurring non-absorbable polyelectrolytes, on the gastrointestinal absorption of strontium was studied in human subjects. The data obtained show that the uptake of ingested strontium from green tea was reduced by a factor of 1.4 in comparison to aqueous solution, whereas administration of black tea had a less pronounced effect on strontium absorption. Addition of alginates in milk resulted in a large reduction of the f1 value by a factor of about 20. Investigations with pectin indicate that this is also a possible inhibitor of strontium uptake. Alginates and pectin therefore seem to be effective nutritional factors to reduce the strontium uptake into the systemic part of the body, which in turn results in a corresponding reduction of the effective dose after ingestion of radionuclides of strontium.