This rat study tested whether alginate, a seaweed-derived polysaccharide used as a food additive, binds strontium and cesium and reduces their absorption. Both sodium and calcium alginate diets lowered plasma strontium and blunted absorption of an oral strontium chloride dose. Calcium alginate was judged safer because the sodium form produced kidney mineralization.
Key numbers
- In vitro, sodium alginate bound strontium concentration-dependently; strontium recovered in filtrate was under 11 percent of control at 1 to 5 mg/mL alginate; EC50 0.296 mg/mL (Results, p. 2).
- Baseline plasma strontium in six-week-old rats was 301.8 plus or minus 45.5 ng/mL; after one week it fell to 65 percent (sodium alginate, 170.7 ng/mL) and 63 percent (calcium alginate, 162.1 ng/mL) of control, and after two weeks to 77 percent and 66 percent (Results, p. 2).
- After an oral dose of strontium chloride (1 mg/kg), Cmax was 108 plus or minus 43 ng/mL in controls versus 58 plus or minus 34 (sodium alginate) and 37 plus or minus 13 ng/mL (calcium alginate); AUC 0 to 3 h 80 versus 33 and 24 ng h/mL (Table 1, p. 3; n = 5).
- Kidney pelvic and papillary mineralization with epithelial hyperplasia appeared in the sodium alginate group only (Table 4, p. 6).
- The authors state that the IAEA recommends 4 g per person per day of sodium alginate for patients exposed to large amounts of radioactive strontium (Introduction, p. 1; Discussion, p. 5).
Methods (brief)
Strontium binding by sodium alginate was tested by ultrafiltration with graphite furnace atomic absorption measurement. Rats were fed diets containing 10 percent sodium or calcium alginate for two weeks; plasma strontium and cesium were followed, then oral strontium chloride or cesium chloride was given and plasma kinetics measured. Safety was assessed by blood chemistry and histopathology.
Evidence fitness
Supports animal evidence that dietary alginate reduces gastrointestinal uptake of stable strontium. It does not establish human efficacy, effective human doses, or strontium concentrations in foods.
Limitations
Two of the nine authors are employees of the alginate manufacturer that supplied the test materials, which is a potential conflict of interest; the paper declares no conflict. Stable strontium was used as a stand-in for radiostrontium. Groups were small (n = 5), and the alginate dose (10 percent of diet) is far above typical human intake.
Related evidence
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