Retinol and carotenoid levels are typically measured in plasma or serum because blood samples are easy to collect. Most of the body’s vitamin A is stored in the liver in the form of retinyl esters. Retinol is then oxidized to retinal and retinoic acid, the two main active vitamin A metabolites in the body. Retinyl esters and provitamin A carotenoids are converted to retinol after uptake into the lumen (for retinyl esters) or absorption (for provitamin A carotenoids). The various forms of vitamin A are solubilized into micelles in the intestinal lumen and absorbed by duodenal mucosal cells. Other carotenoids in food, such as lycopene, lutein, and zeaxanthin, are not converted into vitamin A and are referred to as non-provitamin A carotenoids they might have other important activities not involving vitamin A formation. The main provitamin A carotenoids in the human diet are beta-carotene, alpha-carotene, and beta-cryptoxanthin. Provitamin A carotenoids are plant pigments that the body converts into vitamin A in the intestine. Preformed vitamin A is found in foods from animal sources, including dairy products, eggs, fish, and organ meats. The human diet contains two sources for vitamin A: preformed vitamin A (retinol and retinyl esters) and provitamin A carotenoids. Vitamin A is also critical for vision as an essential component of rhodopsin, the light-sensitive protein in the retina that responds to light entering the eye, and because it supports the normal differentiation and functioning of the conjunctival membranes and cornea. Vitamin A supports cell growth and differentiation, playing a critical role in the normal formation and maintenance of the heart, lungs, eyes, and other organs. Vitamin A is involved in immune function, cellular communication, growth and development, and male and female reproduction. Vitamin A is the name of a group of fat-soluble retinoids, primarily retinol and retinyl esters. For a general overview of Vitamin A and Carotenoids, see our consumer fact sheet on Vitamin A and Carotenoids. Sivalingam.This is a fact sheet intended for health professionals. Please take a moment to view a video profile of Dr. Sivalingam has been selected by his peers as a “Top Doc” in Philadelphia Magazine. Corticosteroid for Retinal Vein Occlusion (SCORE) Study for the National Eye Institute. He has held exhibits at the American Academy of Ophthalmology and was a co-investigator of the Standard Care vs. He has been co-investigator and principal investigator for many studies dealing with Age-Related Macular Degeneration and Choroidal Neovascularization. He lectures extensively: locally, nationally, and internationally. Sivalingam has authored numerous scientific peer-reviewed publications in ophthalmology journals and has contributed chapters to three major ophthalmology reference text books. He is an active member of the American Academy of Ophthalmology, Retina Society, American Society of Retina Specialists (formerly known as The Vitreous Society), Association for Vision in Research and Ophthalmology, Inter-County Ophthalmological Society, Ophthalmic Club of Philadelphia, Pennsylvania Academy of Ophthalmology, Pennsylvania Medical Society, Philadelphia County Medical Society, and the Wills Eye Hospital Society.ĭr. He is a Clinical Associate Professor at Sidney Kimmel Medical College at Thomas Jefferson. Sivalingam is board certified in Ophthalmology and on staff at the Wills Eye Hospital, where he serves as the Co-Director of the Retina Service as well as the Director of the Retina Fellowship. After completing his vitreoretinal training, he joined Ophthalmic Partners of Pennsylvania (OPP) and in 2009, with all the retina physicians of OPP, joined Mid Atlantic Retina.ĭr. He finished his fellowship for Retinal Diseases at Wills Eye Hospital in June 1991. Sivalingam went on to Thomas Jefferson University Hospital for his internship and completed his residency at Wills Eye Hospital where he was selected a co-chief resident. He received his medical degree from the University of Medicine and Dentistry of New Jersey, Rutgers Medical School. Arunan Sivalingam graduated from Franklin and Marshall College in 1981. Undergraduate: Franklin and Marshall Collegeĭr.Medical School: University of Medicine and Dentistry of New Jersey.
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