Retinol (Vitamin A)
Retinol in Serum
Vitamin A is collective term for a group of fat-soluble compounds called retinoic acids1. Vitamin A is a fat-soluble vitamin which should be ingested daily because the human body is unable to synthesize it2, 3.
Vitamin A is needed for growth, reproduction, maintenance of vision and epithelial cellular integrity, and to fight off disease3, 4.
Signs and Symptoms of Deficiency or Toxicity
Vitamin A deficiency occurs as a result of inadequate intake of vitamin A rich foods; lack of fat or oil in the diet to aid in vitamin A absorption; poor absorption or rapid utilization due to illness such as measles, and non-breastfeeding2.
Vitamin A deficiency is reversible during the beginning stages. As the deficiency progresses, the potential of reversing the signs become lower to none. Nyctalopia and Bitot’s spot are early symptoms. Meanwhile, a dry, hazy, and rough-appearing cornea, crater-like defect on cornea, soften cornea, and xerophthalmia are indications that vitamin A deficiency have progressed and the resulting eye problem is no longer reversible2.
Among children, the following may be observed: loss of bone density in susceptible individuals; bulging of anterior fontanelle due to increased intracranial tension, mental retardation, or death5.
Biomarker and Methods of Analysis
RETINOL IN SERUM.
Assessment of the liver is the gold standard for vitamin A assessment but is not feasible for human studies. As such, serum retinol is an alternative to assessment of liver stores and the ideal biomarker for Vitamin A as they are not excreted through urine but stored in the liver. It provides an indication of very low liver storage1.
Identified targets for vitamin supplementation are children < 5 y.o. Universal supplementation must be administered every 6 months to all children 6-59 months2.
Other identified targets for supplementation are high risk children, pregnant and post-partum women2, 7.
Below are the guidelines for supplementation per target group.
- Infants, 6-11 months: 1 dose only of 100,000 IU (1 capsule is given anytime during the 6-11 months but usually given at 9 months of age during the measles immunization)
- Children 12-71 months: 1 capsule every 6 months of 200,000 IU
- Among high-risk children:
- those with measles (infants, 6-11 mos): 100,000 IU, 1 capsule given upon dignosis, regardless of when the last dose of VAC was given
- Severe pneumonia, persistent diarrhea, malnutrition (infants, 6-11 months): 100,000 IU, 1 capsule given upon diagnosis, except when the child was given VAC less than 4 weeks before diagnosis
- Severe pneumonia, persistent diarrhea, malnutrition (12-71 months): 200,000 IU, 1 capsule given upon diagnois, except when child was given VAC less than 4 weeks before diagnosis
- malnutrition (6-12 y.o.): 200,000 IU, 1 capsule given upon diagnosis, except when the child was given VAC less than 4 weeks before diagnosis
- pregnant women: 10,000 IU, 1 capsule/tablet of 10,000 IU twice/wk starting from the 4th month of pregnancy till delivery (Note: Vitamin A 10,000 IU should NOT be given to pregnant women who are already taking prenatal vitamins or multiple micronutrients that contain vitamin A).
- post-partum women: 200,000 IU, 1 capsule, 1 dose only within 4 weeks after delivery (Vitamin A 200,000 IU should not be given to pregnant women7.
Following are the established upper limits per age group8.
- For 6 months to 3 years old: 600 mcg RE
- For 4-8 y.o.: 900 mcg RE
- For 9-13 y.o.: 1700 mcg RE
- For 14-18 y.o.: 2800 mcg RE
- For adults, 19 years and older: 3000 mcg RE
- For pregnant and lactating, 14-18 y.o.: 2800 mcg RE
Vitamin A may interact with certain medications and can cause a reduction of vitamin A levels. These include but are not limited to Orlistat, and retinoids9.
Preformed vitamin A is typically found in foods of animal origin or foods that have been fortified. Examples of which include beef liver, fortified cereal, eggs, butter, fortified milk10.
(1) Diab L, Krebs NF. Vitamin Excess and Deficiency. Pediatrics in Review 2018; 39(4): 161-179.
(2) Department of Health. (n.d.). Philippine Health Advisories. Vitamin A. Retrieved from http://caro.doh.gov.ph/wp-content/uploads/2014/09/VAD.pdf
(3) Food Agriculture Organization. (n.d.) Chapter 7. Vitamin A. Retrieved from http://www.fao.org/docrep/004/y2809e/y2809e0d.htm
(4) Tanumihardjo, Sherry A. Vitamin A: biomarkers of nutrition for development. Am J Clin Nutr 2011; 94(suppl):658S-665S
(5) Bhattacharya S and Singh Amarjeet. Phasing out of the universal megadose of vitamin A prophylaxis to avoid toxicity. AIMS Public Health 2017; 4: 38-46.
(6) Ross AC, Pasatiempo AM, Green MH. Chylomicron margination, lipolysis, and vitamin A uptake in the lactating rat mammary gland: implications for milk retinol content. Exp Biol Med (Maywood) 2004; 229: 46-55.
(7) Department of Health. (December 2003). Administrative Order No 119 s.2003. Updated Guidelines on Micronutrient Supplementation (Vitamin A, Iron, and Iodine). Retrieved from https://ww2.fda.gov.ph/attachments/article/156562/AO119%20Update%20Guidelines%20on%20Micronutrient%20Supplementation%20(Vitamin%20A,%20Iron,%20and%20Iodine%7D.pdf
(8) Philippine Dietary Reference Intakes. 2015. Department of Science Technology-Food and Nutrition Research Institute.
(9) Office of Dietary Supplements-National Institutes of Health. (n.d.). Vitamin A. Fact Sheet for Health Professionals. Retrieved from https://ods.od.nih.gov/factsheets/VitaminA-HealthProfessional/#h9
(10) Linus Pauling Institute. Oregon State University. (n.d.). Micronutrients for Health. Retrieved from http://lpi.oregonstate.edu/sites/lpi.oregonstate.edu/files/pdf/mic/micronutrients_for_health.pdf