both pale and brown oils being used. The trigger for the surge in oral use was the observation made in several European countries--starting with Germany in the 1820s and spreading to other countries into the 1860s--that young children fed cod liver oil did not develop rickets. In northern Europe and the United States, the practice of giving children cod liver oil to prevent rickets persisted well in the 1950s. This overlapped with the fortification of cow's milk with vitamin D, which began in the early 1930s.

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