The demonstration that many foods acquire potencies of noteworthy therapeutic value through the action of ultraviolet rays on the natural edible substances has not only opened up new fields for physiologic investigation but also presented many problems that lie within the domain of pathogenesis. This situation is accentuated by the discovery that a readily prepared organic substance, the unsaturated alcohol ergosterol, is the most significant if not the sole compound that can readily be changed by irradiation so that it acquires the properties of the postulated vitamin D, the so-called antirachitic vitamin. The enormous potency of irradiated or "activated" ergosterol, as measured by the dosage required to produce unmistakable ricketshealing or rickets-preventing effects, has already been referred to on various occasions in The Journal.1 In children the dosage need not exceed 2 mg. (1/30 grain) a day; and the lower limits of effective administration still remain to be determined.
IRRADIATED ERGOSTEROL—A REMINDER. JAMA. 1929;92(24):2023–2024. doi:10.1001/jama.1929.02700500035012