Why are dark green vegetables such as kale and spinach good sources of vitamin a? why are dark green vegetables such as kale and spinach good sources of vitamin a? they contain vitamin c precursors of retinol. they contain the most abundant preformed vitamin a. they contain abundant beta-carotene, a precursor of retinol. they are fortified with vitamin a?

The correct answer is that they contain abundant beta-carotene, a precursor of retinol.
Pre-formed vitamin A exists only in animal products but there are carotenoids that the body can convert into vitamin A and the most common of them is beta-carotene. The body actively converts carotenoids into retinoids (a form of vitamin A). Eating vegetables which are high in beta-carotene (such as spinach and kale) with some fat can increase both the absorption and synthesis of vitamin A.