Creative Bioscience 30 Day Diet Dietary Supplement Capsules ReviewsWholesale Nutritional Supplements ! ![]() ![]() Vitamin A — Health Professional Fact Sheet. Introduction. Vitamin A is the name of a group of fat- soluble retinoids, including retinol, retinal, and retinyl esters . Vitamin A is involved in immune function, vision, reproduction, and cellular communication . ![]() ![]() Also known as The Swedish Diet, The One Week Diet System is a meal-replacement plan that relies on consuming special drinks in place of breakfast. Diet Your Guide To Understanding Dietary Supplement Regulations If you listen to some critics, you probably think there's zero control over the supplement industry. What is the Advocare 24-Day Challenge? First off, the Advocare 24-Day Challenge is a ![]() 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 . 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 . Preformed vitamin A is found in foods from animal sources, including dairy products, fish, and meat (especially liver). By far the most important provitamin A carotenoid is beta- carotene; other provitamin A carotenoids are alpha- carotene and beta- cryptoxanthin. The body converts these plant pigments into vitamin A. Both provitamin A and preformed vitamin A must be metabolized intracellularly to retinal and retinoic acid, the active forms of vitamin A, to support the vitamin's important biological functions . Taking an elemental calcium supplement may increase your risk of heart attack and breast cancer. Fiber supplement benefit, food source, diet, and side effects January 2 2017 by Ray Sahelian, M.D. A high fiber diet that includes a variety of sources of fiber. RTI Project Number 6673-03 Economic Characterization of the Dietary Supplement Industry Contract No. 223-96-2290: Task Order 3 Final Report March 1999. The DASH diet (Dietary Approaches to Stop Hypertension) is a dietary pattern promoted by the U.S.-based National Heart, Lung, and Blood Institute Other carotenoids found in food, such as lycopene, lutein, and zeaxanthin, are not converted into vitamin A. The various forms of vitamin A are solubilized into micelles in the intestinal lumen and absorbed by duodenal mucosal cells . Both retinyl esters and provitamin A carotenoids are converted to retinol, which is oxidized to retinal and then to retinoic acid . Most of the body's vitamin A is stored in the liver in the form of retinyl esters. Retinol and carotenoid levels are typically measured in plasma, and plasma retinol levels are useful for assessing vitamin A inadequacy. However, their value for assessing marginal vitamin A status is limited because they do not decline until vitamin A levels in the liver are almost depleted . 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 . A plasma retinol level increase of at least 2. A level . For clinical practice purposes, plasma retinol levels alone are sufficient for documenting significant deficiency. A plasma retinol concentration lower than 0. L (or 2. 0 micrograms . 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. Recommended Intakes. 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) . DRI is the general term for a set of reference values used for planning and assessing nutrient intakes of healthy people. These values, which vary by age and gender, include: Recommended Dietary Allowance (RDA): average daily level of intake sufficient to meet the nutrient requirements of nearly all (9. Adequate Intake (AI): established when evidence is insufficient to develop an RDA and is set at a level assumed to ensure nutritional adequacy. Estimated Average Requirement (EAR): average daily level of intake estimated to meet the requirements of 5. It is usually used to assess the adequacy of nutrient intakes in population groups but not individuals. Tolerable Upper Intake Level (UL): maximum daily intake unlikely to cause adverse health effects. RDAs for vitamin A are given as mcg of retinol activity equivalents (RAE) to account for the different bioactivities of retinol and provitamin A carotenoids (see Table 1). Because the body converts all dietary sources of vitamin A into retinol, 1 mcg of physiologically available retinol is equivalent to the following amounts from dietary sources: 1 mcg of retinol, 1. From dietary supplements, the body converts 2 mcg of beta- carotene to 1 mcg of retinol. Currently, vitamin A is listed on food and supplement labels in international units (IUs) even though nutrition scientists rarely use this measure. Conversion rates between mcg RAE and IU are as follows . Food and Drug Administration (FDA) mandates that older conversion factors published by the FNB in 1. IU = 0. 3 mcg as retinol = 0. Under FDA's new labeling regulations for foods and dietary supplements that take effect by July 2. July 2. 6, 2. 01. A will be listed only in mcg and not IUs . For example, the RDA of 9. RAE for adolescent and adult men is equivalent to 3,0. IU if the food or supplement source is preformed vitamin A (retinol). However, this RDA is also equivalent to 6,0. IU of beta- carotene from supplements, 1. IU of beta- carotene from food, or 3. IU of alpha- carotene or beta- cryptoxanthin from food. So a mixed diet containing 9. RAE provides between 3,0. IU of vitamin A, depending on the foods consumed. Table 1: Recommended Dietary Allowances (RDAs) for Vitamin A . Other sources of preformed vitamin A are milk and eggs, which also include some provitamin A . Most dietary provitamin A comes from leafy green vegetables, orange and yellow vegetables, tomato products, fruits, and some vegetable oils . The top food sources of vitamin A in the U. S. The foods from animal sources in Table 2 contain primarily preformed vitamin A, the plant- based foods have provitamin A, and the foods with a mixture of ingredients from animals and plants contain both preformed vitamin A and provitamin A. Table 2: Selected Food Sources of Vitamin A . DVs were developed by the FDA to help consumers compare the nutrient contents of products within the context of a total diet. The DV for vitamin A is 5,0. IU for adults and children age 4 and older. Foods providing 2. DV are considered to be high sources of a nutrient. Department of Agriculture's (USDA's) Nutrient Database Web site . A portion of the vitamin A in some supplements is in the form of beta- carotene and the remainder is preformed vitamin A; others contain only preformed vitamin A or only beta- carotene. Supplement labels usually indicate the percentage of each form of the vitamin. The amounts of vitamin A in stand- alone supplements range widely . Multivitamin supplements typically contain 2,5. IU vitamin A, often in the form of both retinol and beta- carotene. About 2. 8%–3. 7% of the general population uses supplements containing vitamin A . Adults aged 7. 1 years or older and children younger than 9 are more likely than members of other age groups to take supplements containing vitamin A. Vitamin A Intakes and Status. According to an analysis of data from the 2. National Health and Nutrition Examination Survey (NHANES), the average daily dietary vitamin A intake in Americans aged 2 years and older is 6. RAE . Adult men have slightly higher intakes (6. RAE) than adult women (5. RAE). Although these intakes are lower than the RDAs for individual men and women, these intake levels are considered to be adequate for population groups. Data from NHANES III, conducted in 1. A in RAEs consumed by men and 3. United States comes from provitamin A carotenoids, with the remainder coming from preformed vitamin A, mostly in the form of retinyl esters . Furthermore, girls and African- American children have a higher risk of consuming less than two- thirds of the vitamin A RDA than other children . However, vitamin A deficiency is common in many developing countries, often because residents have limited access to foods containing preformed vitamin A from animal- based food sources and they do not commonly consume available foods containing beta- carotene due to poverty . According to the World Health Organization, 1. L . In these countries, low vitamin A intake is most strongly associated with health consequences during periods of high nutritional demand, such as during infancy, childhood, pregnancy, and lactation. In developing countries, vitamin A deficiency typically begins during infancy, when infants do not receive adequate supplies of colostrum or breast milk . Chronic diarrhea also leads to excessive loss of vitamin A in young children, and vitamin A deficiency increases the risk of diarrhea . The most common symptom of vitamin A deficiency in young children and pregnant women is xerophthalmia. One of the early signs of xerophthalmia is night blindness, or the inability to see in low light or darkness . Vitamin A deficiency is one of the top causes of preventable blindness in children . People with vitamin A deficiency (and, often, xerophthalmia with its characteristic Bitot's spots) tend to have low iron status, which can lead to anemia . Vitamin A deficiency also increases the severity and mortality risk of infections (particularly diarrhea and measles) even before the onset of xerophthalmia . 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 . Preterm infants with vitamin A deficiency have an increased risk of eye, chronic lung, and gastrointestinal diseases . But in women with vitamin A deficiency, breast milk volume and vitamin A content are suboptimal and not sufficient to maintain adequate vitamin A stores in infants who are exclusively breastfed . The prevalence of vitamin A deficiency in developing countries begins to increase in young children just after they stop breastfeeding . The most common and readily recognized symptom of vitamin A deficiency in infants and children is xerophthalmia. Pregnant and Lactating Women in Developing Countries. Pregnant women need extra vitamin A for fetal growth and tissue maintenance and for supporting their own metabolism . The World Health Organization estimates that 9.
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