In addition, the evolution of the recommended dietary intakes of vitamin A will be discussed.
Elmer V. McCollum and M. Davis discovered vitamin A during 1912-1914. In 1913, Yale researchers, Thomas Osborne and Lafayette Mendel discoveredthat butter contained a fat-soluble nutrient soon known as vitamin A. Scientist of this era had determined that there was vitamin A activity from yellow pigmentation in plants that was similar to the yellow in butterfat. Early researchers went on to deny the possibility of a relationship between yellow coloration in plants and vitamin A activity based on findings from Palmer and Eccles, 1914. Palmer and Eccles achieved success in rearing chickens and rats up with diets almost devoid of carotene. In addition, Stephenson  found that butter fat could be completely stripped of color by charcoal without losing its retinol activity.
It was not until 1929 when the link between carotene and vitamin A activity was reestablished. Thomas Moore in 1929 continued research between carotene and vitamin A activity in rats from carrot root. In Moore's experiment test rats were fed a vitamin A restricted diet until definite signs of deficiency become obvious, Xerophthalmia (night blindness) and slowed growth. Fresh carrot root cut into pieces of 50, 100 or 200 mg. were added to the rodents daily intake. ...Show more