|Vitamin :: Vitamin A|
|Other Terms:||Retinol | Retinal | Beta-carotene|
|Solubility:||Fat soluble, which means it needs to be taken with fats to be absorbed in the digestive system. It is stored by the body in the liver.|
|On this Page:||What is Vitamin A · Benefits · Deficiency Signs · Foods · Supplements · RDA · Toxicity | Overdose|
It is the name of a group of compounds that include retinol, retinoic acid, and retinal. As with most vitamins, it cannot be made in the body and can only be obtained through food and supplements.
There are two main forms of vitamin A, depending on food source. Vitamin A from animal sources is absorbed as retinol, which can be converted into retinal and retinoic acid in the body. Retinol can be toxic in large doses.
Plants do not provide vitamin A. Instead they contain pro-vitamin A carotenoids that can be made into vitamin A by our bodies. Unlike retinol, carotenoids are not toxic in large amounts. They are potent antioxidants and aid in cancer prevention. Of all the carotenoids, beta-carotene is the most common, and most easily converted to retinol.
Vitamin A is probably best known for its role in preventing night blindness and other vision problems. What is less known is that it is also important for bone growth, reproduction, and cell division.
It helps the immune system to fight infections by making the white blood cells that destroy viruses and bacteria. It also promotes healthy skin and mucous linings that act as a barrier against the viruses and bacteria.
|::||Vitamin A Benefits & Functions|
|1.||essential for healthy eyes, and prevents night blindness and weak eye sight|
|2.||studies indicate a protective effect against common eye disorders such as cataracts|
|3.||found to protect against macular degeneration of the eyes that leads to loss of vision in the center of the visual field|
|4.||promotes normal working of the reproductive system in both males and females, including during pregnancy and lactation|
|5.||important in the development of bones and teeth|
|6.||powerful antioxidant that protects body cells and tissues against cancer and cardiovascular disease, by neutralizing the free radical damage that is believed to lead to the diseases; studies have shown that high intake of vitamin A and/or carotenoids may help lower the risk of some cancers|
|7.||known to have strong anti-viral activity and to enhance the function of white blood cells and strengthen the immune system against colds, flu, and infections of the kidneys, bladder, lungs and mucous membranes|
|8.||promotes healthy surface linings of the eyes and respiratory, urinary, and intestinal tracts, as a protective barrier against viruses and bacteria entering the body and causing infection|
|9.||promotes healthy hair and nails|
|10.||may prevent skin problems like acne, promote healthy wrinkle-free skin, and help remove age spots|
|11.||slows the aging process (anti-aging)|
Vitamin A Deficiency Symptoms and Causes
Vitamin A deficiency symptoms might arise from a lack in the diet, or poor absorption due to gastrointestinal problems. Antibiotics, some cholesterol lowering drugs and laxatives are also known to hinder vitamin A absorption.
This list summarizes the main vitamin A deficiency symptoms.
|::||Vitamin A Deficiency Symptoms|
|1.||faulty teeth and slow bone formation, and growth retardation in children|
|2.||night blindness (poor eyesight in dim light)|
|3.||prolonged deficiency can cause xerophthalmia (dry eyes) by making the cornea very dry, leading to ulcerations that damage the retina and cornea, and that may ultimately cause blindness|
|4.||rough dry scaly skin (xerosis) that may lead to small cracks in the skin|
|5.||follicular hyperkeratosis (goosebump-like deposits of keratin that form around hair follicles, causing bumps on the skin, mainly on the back, upper arm, shoulders, neck, buttocks, lower abdomen, and legs)|
|6.||increased susceptibility to colds and infections, especially in the throat and lungs, for instance to pneumonia and measles|
|7.||sinusitis (chronic inflammation of the sinuses)|
|8.||frequent infections of the bladder or urinary tract|
|9.||tendency to abcesses in the ears|
|10.||rapid weight loss|
|11.||loss of smell, taste or appetite|
Vitamin A Foods
High vitamin A foods
· animal liver · fish liver oil.
Other foods with vitamin A
· eggs · milk · foods containing beta-carotene (which is converted to vitamin A in the liver) such as green and yellow vegetables like alfalfa, asparagus, beets, broccoli, chilli peppers, carrots, kale, mustard, spinach, spirulina, pumpkin and yellow squash, sweet potatoes, and reddish-yellow fruits like apricots, cantaloupe, mangoes, papaya, peaches.
Vitamin A Supplements
Taking vitamins and minerals in their correct balance is vital to the proper functioning of all vitamins. They work synergistically, which means that the effectiveness of any one nutrient requires or is enhanced, sometimes dramatically, by the presence of certain other nutrients.
For this reason, if you are looking to take supplements for maintenance of optimal health, the recommended approach is to take a multi-vitamin that has the proper balance of all the necessary nutrients your body needs.
For a list of reputable top ranked vitamin and mineral supplements chosen in an independent supplement review, see Best Multivitamin Supplements. Many of these are manufactured to pharmaceutical or nutraceutical GMP compliance, which is the highest multivitamin standard possible.
Keep in mind, however, that while vitamin supplements are useful to plug nutritional gaps that are almost inevitable in modern diets, and to ensure we get optimal doses ofnutrients, they are no substitute for a good diet. Instead, use them to complement a healthy diet and lifestyle.
Vitamin A RDA (Recommended Dietary Allowance)
The Food & Nutrition Board of the Institute of Medicine, National Academy of Sciences, in their 1997-2001 collaboration between the US and Canada, set the daily Adequate Intake (AI) of Vitamin A as follows.
|Life Stage | Gender||Vitamin A Dosage | Day|
|Infants 0-6 mths||400* µg|
|Infants 7-12 mths||500* µg|
|Children 1-3 yrs||300 µg|
|Children 4-8 yrs||400 µg|
|Girls 9-13 Yrs||600 µg|
|Boys 9-13 Yrs||600 µg|
|Females 14-18 Yrs||700 µg|
|Males 14-18 Yrs||900 µg|
|Females 19-50 Yrs||700 µg|
|Males 19-50 Yrs||900 µg|
|Females older than 50 Yrs||700 µg|
|Males older than 50 Yrs||900 µg|
|Pregnant Women 14-18 Yrs||750 µg|
|Pregnant Women 19-50 Yrs||770 µg|
|Lactating Mothers 14-18 Yrs||1200 µg|
|Lactating Mothers 19-50 Yrs||1300 µg|
These dosages are the minimum required per day to ward off deficiency. In therapeutic use of this nutrient, dosage is increased as necessary for the ailment, keeping in mind Vitamin A toxicity levels.
1 µg = 1 mcg = 1 microgram = 1/1,000,000 of a gram
1 mg = 1 milligram = 1/1,000 of a gram
* Indicates AI figures based on Dietary Reference Intake (DRI) figures
Vitamin A Overdose Symptoms, Toxicity Level & Side Effects
Excessive consumption, such as from mega-doses carries a risk of vitamin A toxicity, as it is a fat-soluble vitamin that is stored in the body.
Symptoms of vitamin A overdose include itchy dry skin, headache, nausea, abdominal pain, irritability and fatigue. Severe vitamin A overdose can lead to blurred vision, dizziness, vomiting, bone abnormalities and joint pain. Symptoms disappear when excess intake stops.
A safe form of vitamin A is beta-carotene, which is converted to vitamin A in the liver. There is no risk of overdose, though the skin may turn slightly orange, as excess beta-carotene is excreted in urine, turning it yellow.
However diabetics and those with hypothyroid should avoid beta-carotene as they cannot convert it to vitamin A.
The Food and Nutrition Board of the Institute of Medicine has set Tolerable Upper Intake Levels (ULs) for vitamin A. These are the highest average daily intake levels above which there is risk of vitamin A toxicity, especially if taken over a long time.
|Life Stage||Tolerable Upper Intake Levels (UL) per Day|
|0 to 3 years||600 µg (2,000 IU or 400 RE)|
|4 to 8 years||900 µg (3,000 IU or 600 RE)|
|9 to 13 years||1,700µg (5,500 IU or 1,100 RE)|
|14 to 18 years*||2,800µg (9,250 IU or 1,850 RE)|
|19 years and above*||3,000µg (10,000 IU or 2,000 RE)|
*Includes pregnant and breastfeeding women
The ULs do not apply to therapeutic use of vitamin A for treatment, which should be under the supervision of a healthcare professional.
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|1.||Institute of Medicine, Food and Nutrition Board. Dietary reference intakes for vitamin A, vitamin K, arsenic, boron, chromium, copper, iodine, iron, manganese, molybdenum, nickel, silicon, vanadium, and zinc. Washington, DC: National Academy Press; 2001.|
|2.||U.S. National Libary of Medicine [NLM] & National Institutes of Health [NIH]: MedlinePlus. NLM-NIH home page. <http://www.nlm.nih.gov/medlineplus>. Use the built-in search function to find specific data. Accessed 2009 March – June.|
|3.||National Institutes of Health, NIH Clinical Center: Office of Dietary Supplements [ODS]. ODS home page. <http://ods.od.nih.gov>. Use the built-in search function to find specific data. Accessed 2009 Mar – Jun.|
|4.||The George Mateljan Foundation: The world’s healthiest foods [WHFoods]. WHFoods home page. <http://www.whfoods.com>. Accessed 2009 March – June.|
|5.||Balch JF, Balch PA. Prescription for nutritional healing: A practical A-Z reference to drug-free remedies using vitamins, minerals, herbs & food supplements. Garden City Park, New York: Avery Publishing; 1990.|
|6.||Ulene A. Dr. Art Ulene’s complete guide to vitamins, minerals and herbs. New York, NY: Avery Publishing; 2000.|