[Problem] To provide a new technology with which it is possible to further increase a supply amount of divalent iron. [Solution] Provided is a divalent iron supply agent that contains: a hydrothermal reaction treatment product of a mixture containing at least one of yeast, a yeast extract, and a yeast cell wall, at least one of phosphoric acid and a phosphoric acid compound, and at least one of potassium and a potassium compound; and an iron supply raw material.