A vitamin precursor that the body converts to its active form through normal metabolic processes. Carotene for example is a provitamin of vitamin a.

维生素原一种由身体通过正常新陈代谢过程，将其转化成活跃形式的维生素的前体，比如，胡萝卜素是维生素a的维生素原。

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Beta carotene is a type of carotenoid, a plant pigment that is a provitamin for vitamin A. During its digestion and metabolism, a percentage is converted to vitamin A, a fat-soluble vitamin that is important for vision, growth and development, and healthy immune and reproductive function.

CNN: Should I take beta carotene as a supplement?