Vitamin A, a bi-polar molecule formed with bi-polar covalent bonds between carbon and hydrogen, is linked to a family of similarly shaped molecules, the retinoids, which complete the remainder of the vitamin sequence. Its important part is the retinyl group, which can be found in several forms. In foods of animal origin, the major form of vitamin A is an ester, primarily retinyl palmitate, which is converted to an alcohol (retinol) in the small intestine. Vitamin A can also exist as an aldehyde (retinal), or as an acid (retinoic acid). Precursors to the vitamin (provitamins) are present in foods of plant origin as some of the members of the carotenoid family of compounds. Vitamin A is found naturally in many foods: * liver (beef, pork, chicken, turkey, fish) (6500 μg 722%) * carrots (835 μg 93%) * Broccoli leaves (800 μg 89%) - Acc. to USDA database. Broccoli florets supposedly have much less - see note[10]. * sweet potatoes (709 μg 79%) * kale (681 μg 76%) * butter (684 μg 76%) * spinach (469 μg 52%) * leafy vegetables * pumpkin (369 μg 41%) * collard greens (333 μg 37%) * cantaloupe melon (169 μg 19%) * eggs (140 μg 16%) * apricots (96 μg 11%) * papaya (55 μg 6%) * mango (38 μg 4%) * peas (38 μg 4%) * broccoli (31 μg 3%) * winter squash