JAMA. 1930;95(13):937. doi:10.1001/jama.1930.02720130033013.
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Vitamin A is one of the earliest recognized food factors now known to be as essential to well being as are proteins, other energy-yielding nutrients, and inorganic salts. In the course of the preliminary studies that were devoted to ascertaining the distribution of this fat-soluble substance in natural foods, it became apparent that various materials rich in vitamin A also exhibited the color characteristic of so-called carotinoid pigments. This was true not only of egg fat, butter and carrots but also of Indian corn, or maize. In fact, investigation has repeatedly demonstrated an apparent parallelism between the color of corn and its content of vitamin A, "white" corn being comparatively devoid of the A factor. Green leaves known to be rich in vitamin A usually have their carotinoid pigments obscured by the preponderance of the chlorophyll with which such vegetation is richly endowed. Suggestions were early made that vitamin A


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