Vitamin A in the form of retinoic acid is essential for gene transcription. It supports immune function by supporting the growth and distribution of T-cells, a type of white blood cell that protects your body from infection (7). Vitamin A is involved in immune function, vision, reproduction, and cellular communication [ 1, 4, 5 ]. It exists naturally in the foods you eat and can also be consumed through supplements. Objective: Vitamin A and its retinoid derivates play an important role in regulation of normal growth and development. Vitamin A compounds are essential fat-soluble molecules predominantly stored in the liver in the form of retinyl esters (e.g., retinyl palmitate). In fact, both the CARET and ATBC studies showed a significant increase in lung cancer risk among study participants taking beta-carotene supplements or beta-carotene and retinyl palmitate supplements. J Nutr 2011;141:261-6. Because vitamin A is fat soluble, it’s stored in body tissue for later use. Here is a summary of the main functions (and benefits) the nutrient offers. Learn more. In the ATBC study, beta-carotene supplements (20 mg daily) were also associated with increased mortality, mainly due to lung cancer and ischemic heart disease . Vitamin E is an antioxidant, which protects body cells from damage. This is a fact sheet intended for health professionals. Vitamin A toxicity may cause symptoms, such as liver damage, vision disturbances, nausea and even death. Retinal plays an important role in vision. Converting Units of Measure for Folate, Niacin, and Vitamins A, D, and E on the Nutrition and Supplement Facts Labels: Guidance for Industry. Bailey RL, Gahche JJ, Lentino CV, Dwyer JT, Engel JS, Thomas PR, et al. Although excess preformed vitamin A can have significant toxicity (known as hypervitaminosis A), large amounts of beta-carotene and other provitamin A carotenoids are not associated with major adverse effects . Most of the vitamin A in your body is kept in your liver in the form of retinyl esters (3). This section focuses on three diseases and disorders in which vitamin A might play a role: cancer, age-related macular degeneration (AMD), and measles. about your interest in, questions about, or use of dietary supplements and what may be best for your overall health. Retinol not only creates the pigments in the retina of the eye, according to NLM, but also is integral for good vision, especially night vision, and overall eye health. Vitamin D is important for the absorption and utilization of calcium, and its deficiency leads to weak teeth and bones. Vitamin A also supports cell growth and differentiation, playing a critical role in the normal formation and maintenance of the heart, lungs, kidneys, and other organs . In some studies, high plasma or serum concentrations of some provitamin A carotenoids have been associated with a lower risk of various health outcomes, but these studies have not definitively demonstrated that this relationship is causal. There are two types of vitamin A. It is found in dark green vegetables, whole milk, meats, liver, fish, egg yolk and butter. Cochrane Database Syst Rev 2011:CD007719. The U.S. Department of Agriculture's (USDA's) FoodData Central  lists the nutrient content of many foods and provides a comprehensive list of foods containing vitamin A in IUs arranged by nutrient content and by food name, and foods containing beta-carotene in mcg arranged by nutrient content and by food name. To avoid toxicity, steer clear of high-dose vitamin A supplements. GlaxoSmithKline. Preformed vitamin A — retinol and retinyl esters — occurs exclusively in animal products, such as dairy, liver and fish, while provitamin A carotenoids are abundant in plant foods like fruits, vegetables and oils (2). The DV for vitamin A on the new Nutrition Facts and Supplement Facts labels and used for the values in Table 2 is 900 mcg RAE for adults and children age 4 years and older , where 1 mcg RAE = 1 mcg retinol, 2 mcg beta-carotene from supplements, 12 mcg beta-carotene from foods, 24 mcg alpha-carotene, or 24 mcg beta-cryptoxanthin. Vitamin A is critical for vision as an essential component of rhodopsin, a protein that absorbs light in the retinal receptors, and because it supports the normal differentiation and functioning of the conjunctival membranes and cornea [2-4]. © 2005-2021 Healthline Media a Red Ventures Company. [, O'Neil C, Shevill E, Chang AB. Additionally, vitamin A helps maintain surface tissues such as your skin, intestines, lungs, bladder and inner ear. Observational studies have suggested an association between high intakes of preformed vitamin A (more than 1,500 mcg daily—only slightly higher than the RDA), reduced bone mineral density, and increased fracture risk [1,4,40]. An age-related eye disease study by the National Eye Institute found that taking high levels of antioxidants, such as vitamin A, along with zinc, may reduce the risk of developing advanced age-related macular degeneration by about 25 percent. Vitamin A is possibly effective in preventing cataracts, or slowing the progression of retinitis pigmentosa (an eye disease that causes damage to the retina). Vitamin A as retinyl esters in chylomicrons was also found to have a… Vitamins have diverse biochemical functions. This RDA is also equivalent to 18,000 IU beta-carotene from food or to 36,000 IU alpha-carotene or beta-cryptoxanthin from food. In: Bowman B, Russell R, eds. Beta-Carotene. Get the latest public health information from CDC: https://www.coronavirus.gov
Both retinyl esters and provitamin A carotenoids are converted to retinol, which is oxidized to retinal and then to retinoic acid . [, Age-Related Eye Disease Study Research Group. Additionally, vitamin A deficiency raises the risk of anemia and death in pregnant women and negatively impacts the fetus by slowing growth and development (20). Liver vitamin A reserves can be measured indirectly through the relative dose-response test, in which plasma retinol levels are measured before and after the administration of a small amount of vitamin A . This article tells you all you need to know about…. Cancer Epidemiol Biomarkers Prev 2009;18:2202-6. Our website services, content, and products are for informational purposes only. Vitamin C (ascorbic acid) is a strong antioxidant known for strengthening the immune system by fighting off colds and other infectious diseases. Total intakes of preformed vitamin A that exceed the UL and some synthetic retinoids used as topical therapies (such as isotretinoin and etretinate) can cause congenital birth defects [2-4]. Estimated Average Requirement (EAR): Average daily level of intake estimated to meet the requirements of 50% of healthy individuals; usually used to assess the nutrient intakes of groups of people and to plan nutritionally adequate diets for them; can also be used to assess the nutrient intakes of individuals. The vitamin, which functions directly in vision, is converted into retinaldehyde, a component of a light-sensitive pigment called rhodopsin (visual purple), which is present in the retina of the eye. It’s also critical for placental health, fetal tissue development and maintenance, as well as fetal growth (8). AMD's etiology is usually unknown, but the cumulative effect of oxidative stress is postulated to play a role. [, Graham-Maar RC, Schall JI, Stettler N, Zemel BS, Stallings VA. Elevated vitamin A intake and serum retinol in preadolescent children with cystic fibrosis. Intake recommendations for vitamin A and other nutrients are provided in the Dietary Reference Intakes (DRIs) developed by the Food and Nutrition Board (FNB) at the Institute of Medicine of the National Academies (formerly National Academy of Sciences) . A plasma retinol level increase of at least 20% indicates an inadequate vitamin A level [3,5,6]. Vitamin A is a fat-soluble vitamin that is absorbed with fats in your diet and stored in your body's fatty tissue. Since vitamin A is fat-soluble, it’s stored in your body and can reach unhealthy levels over time. What’s more, test-tube studies demonstrate that retinoids may inhibit the growth of certain cancer cells, such as bladder, breast and ovarian cancer (16). However, the results of studies on this risk have been mixed, so the safe retinol intake level for this association is unknown. Present Knowledge in Nutrition. The federal government's 2015-2020 Dietary Guidelines for Americans notes that "Nutritional needs should be met primarily from foods. What’s more, vitamin A supports healthy skin cells, male and female reproduction and fetal development (8). Other effects of vitamin A deficiency in pregnant and lactating women include increased maternal and infant morbidity and mortality, increased anemia risk, and slower infant growth and development. Adequate Intake (AI): Intake at this level is assumed to ensure nutritional adequacy; established when evidence is insufficient to develop an RDA. Retinoids can increase the risk of hypervitaminosis A when taken in combination with vitamin A supplements . [, van den Broek N, Dou L, Othman M, Neilson JP, Gates S, Gulmezoglu AM. Vitamin A is necessary for support of growth, health and life of all major animal species. [, Darlow BA, Graham PJ. Routine vitamin A supplementation for the prevention of blindness due to measles infection in children. However, preterm infants do not have adequate liver stores of vitamin A at birth and their plasma concentrations of retinol often remain low throughout the first year of life [17,18]. Recommended Dietary Allowance (RDA): Average daily level of intake sufficient to meet the nutrient requirements of nearly all (97%–98%) healthy individuals; often used to plan nutritionally adequate diets for individuals. JAMA 2013;309:2005-15. In developed countries, clinical vitamin A deficiency is rare in infants and occurs only in those with malabsorption disorders . Vitamin A supplements for preventing mortality, illness, and blindness in children aged under 5: systematic review and meta-analysis. J Natl Cancer Inst 2004;96:1743-50. But tattoo allergies go beyond simple irritation — the skin can swell, itch, and…. 1) Vitamin A Enhances Immune Response Carotenoids fight free radicals — highly reactive molecules that can harm your body by creating oxidative stress (9). All rights reserved. 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