Oxalate in vegetable Amaranth (Amaranthus gangeticus). forms, contents, and their possible implications for human health

Forms of oxalate in Amaranthus gangeticus L (a vegetable amaranth) grown in three sites with different soil and climatic factors were identified, and their contents were determined. On average the total oxalate content was 91 g kg−1 on a dry weight basis. This is high when compared with the amounts reported to be a health hazard in other vegetables and forage crops. Two dominant fractions of oxalate in amaranth were isolated: a fraction soluble in boiling water which was predominantly in the form of potassium and magnesium oxalate, and an associated insoluble residue which was predominantly calcium oxalate. Most of the Ca in amaranth is unlikely to be available to the body. A suggestion was made that research on reducing the oxalate content of amaranth should first be directed at soluble oxalates because they can interfere with Ca availability from other food sources.