Vitamin A

Vitamin A was the first of the critical nutritional compounds called vitamins to be discovered. American scientist Elmer V. McCollum identified the compound in his experiments with the nutrition of rats. He found that the rats grew and remained healthy when fed a diet of butter and egg yolk. But if lard or olive oil was substituted for the butter, the rats declined in health and eventually died. Believing that some essential substance was contained in the butter, he extracted a yellow-colored oil from the butter which he called "fat-soluble A", now called vitamin A. Vitamin A or retinol is an alcohol with composition C₂₀H₂₉OH.

维生素A是最早被发现的营养必需化合物之一。美国科学家埃尔默·V·麦科勒姆在研究老鼠营养时发现了这种物质。他发现，当给老鼠喂食黄油和蛋黄时，它们能正常生长并保持健康。但如果用猪油或橄榄油代替黄油，老鼠的健康状况会逐渐恶化，最终死亡。他认为黄油中含有一种本质物质，于是从黄油中提取出一种黄色油状物，称为“脂溶性A”，现在称为维生素A。维生素A或视黄醇是一种醇，其化学式为C₂₀H₂₉OH。

Vitamin A is found in eggs, milk, butter, and green and yellow vegetables. It increases resistance to infection and promotes good night vision (Shipman and Wilson).

维生素A存在于蛋、牛奶、黄油和绿色和黄色蔬菜中。它能增强抗感染能力并促进良好的夜视功能（Shipman和Wilson）。