The vitamin A in foods is classified as either retinol (the active form of
vitamin A) or beta-carotene (a precursor of vitamin A). Retinol is found in
all animal products, while beta-carotene is found in plant products. Retinol
is absorbed more readily than beta-carotene. It appears that it is easier
for the body to absorb the beta-carotene from many dark yellow and orange
fruits and vegetables than from dark green leafy vegetables.