Author information1Department of Physiological Chemistry, University of Lund, Sweden.AbstractThe aim of the present study was to characterize the intestinal absorption of retinol and retinyl palmitate in thoracic duct and bile duct fistulated rats and to investigate the effect of a simultaneously administered lipase inhibitor, tetrahydrolipstatin (THL). Absorption was determined as lymphatic recovery over a 24-hr period, including an initial 12-hr continuous intraduodenal infusion of either [11,12-3H]retinol or [11,12-3H]retinyl palmitate given in emulsified glyceryl trioleate or in mixed micellar solution of monoolein and oleic acid. From micellar dispersion, labeled retinol and retinyl palmitate were recovered in the lymph to 50-60% and both to the same extent. Administered in emulsified form, labeled retinol from fed retinyl palmitate was recovered to 47%, but retinol from fed retinol to only 18%. THL (10(-4) M) in the infusate had no significant effect on the recovery of 14C-labeled oleic acid.
The recovery of label from emulsified glyceryl tri[1-14C]oleate was significantly decreased at this concentration of THL (76.5% vs 19.6% recovery). When administered in emulsified form, retinol absorption was not significantly affected by THL at 10(-4) M, while retinyl palmitate absorption was very significantly decreased (5.0% compared to 47.8%). In the presence of THL, retinol absorption from retinyl palmitate in micellar solution was decreased (from 58% to 17%). Most of the retinol in the lymph extracts (72.2 to 91.3) was present as retinyl ester, regardless of the chemical and physical form of administration. Furthermore, THL did not induce any change in this pattern.PMID: 2250593 [Indexed for MEDLINE] MeSH termsAnimalsBiological Transport/drug effectsCarbon RadioisotopesInfusions, ParenteralIntestinal Absorption/drug effects*Lactones/pharmacology*Lipase/antagonists & inhibitors*Lymph/metabolismMaleMicellesRatsRats, Inbred StrainsScintillation CountingTritiumVitamin A/analogs & derivatives*Vitamin A/pharmacokinetics*SubstancesCarbon RadioisotopesLactonesMicellesTritiumVitamin Aretinol palmitateorlistatLipaseMedicalVitamin A - MedlinePlus Health InformationMiscellaneousVITAMIN A - Hazardous Substances Data BankTRITIUM, RADIOACTIVE - Hazardous Substances Data BankORLISTAT - Hazardous Substances Data Bank
Retinyl palmitate, or vitamin A palmitate, is the ester of retinol (vitamin A) and palmitic acid, with formula C36H60O2. An alternate spelling, retinol palmitate, which violates the -yl organic chemical naming convention for esters, is also frequently seen. Retinyl palmitate is a synthetic alternate for retinyl acetate in vitamin A supplements, and is available in oily or dry forms. It is a common vitamin supplement, available in both oral and injectable forms for treatment of vitamin A deficiency, under the brand names Aquasol A, Palmitate A and many others. It is a constituent of intra ocular treatment for dry eyes at a concentration of 138 µg/g (VitA-Pos) by Ursapharm. It is a pre-formed version of vitamin A; therefore, the intake should not exceed the Recommended Dietary Allowance (RDA). Overdosing preformed Vitamin A forms such as retinyl palmitate leads to adverse physiological reactions (hypervitaminosis A). Retinyl palmitate is used as an antioxidant and a source of vitamin A added to low fat milk and other dairy products to replace the vitamin content lost through the removal of milk fat.
Palmitate is attached to the alcohol form of vitamin A, retinol, in order to make vitamin A stable in milk. Retinyl palmitate is also a constituent of some topically applied skin care products. After its absorption into the skin, retinyl palmitate is converted to retinol, and ultimately to retinoic acid (the active form of vitamin A present in Retin-A). The Environmental Working Group (EWG) and New York Senator Chuck Schumer have called attention to the fact that high doses of topical retinyl palmitate were shown to accelerate cancer in lab animals,[2] fueling the sunscreen controversy in the popular press.[3] One toxicological analysis determined that "there is no convincing evidence to support the notion that [retinyl palmitate] in sunscreens is carcinogenic."[4] EWG disputed the findings, calling the report "faulty" and "misleading."[5] A technical report issued thereafter by the National Toxicology Program concluded that diisopropyl adipate increased incidence of skin tumors in mice, and the addition of either retinoic acid or retinyl palmitate both exacerbated the rate and frequency of tumors.
World Health Organization recommendation on Maternal Supplementation During Pregnancy states that "health benefits are expected for the mother and her developing fetus with little risk of detriment to either, from a daily supplement not exceeding 10,000 IU [preformed] vitamin A (3000 µg RE) at any time during pregnancy."[7] Preformed Vitamin A refers to retinyl palmitate and retinyl acetate. ^ Vitamin A, Linus Pauling Institute ^ National Toxicology Program. (2012). NTP technical report on the photocarcinogenesis study of retinoic acid and retinyl palmitate [CAS Nos. 302-79-4 (All-trans-retinoic acid) and 79-81-2 (All-trans-retinyl palmitate)] in SKH-1 mice (Simulated solar light and topical application study). Accessed September 19, 2013.Skip to main content You are hereVitamins » Vitamin A Meet the staff of the Micronutrient Information Center. If you value this website, please help by donating to the MIC. The Linus Pauling Institute Micronutrient Information Center provides scientific information on the health aspects of dietary factors and supplements, food, and beverages for the general public.
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