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Vitamin A 15.01.12 11:09
Vitamin A What’s Vitamin A? Vitamin A is a fat-soluble vitamin. Two different types of vitamin A are found in the diet. Preformed vitamin A is found in animal products such as meat, fish, poultry and dairy foods. The other type, pro-vitamin A is found in plant-based foods such as fruits and vegetables. The most common type of pro-vitamin A is beta-carotene. Vitamin A is also available in dietary supplements, usually in the form of retinyl acetate or retinyl palmitate (preformed vitamin A), beta-carotene (pro-vitamin A) or a combination of preformed and pro-vitamin A. Function of Vitamin A Vitamin A helps form and maintain healthy skin, teeth, skeletal and soft tissue, mucus membranes, and skin. It is also known as retinol because it produces the pigments in the retina of the eye. Vitamin A promotes good vision, especially in low light. It may also be needed for reproduction and breast-feeding. Retinol is an active form of vitamin A. It is found in animal liver, whole milk, and some fortified foods. Carotenoids are dark-colored dyes (pigments) found in plant foods that can turn into a form of vitamin A. There are more than 500 known carotenoids. One such carotenoid is beta-carotene. • Beta-carotene is an antioxidant. Antioxidants protect cells from damage caused by substances called free radicals. Free radicals are believed to contribute to certain chronic diseases and play a role in the aging processes. • Food sources of carotenoids such as beta-carotene may reduce the risk for cancer. Beta-carotene supplements do not seem to reduce cancer risk. Food Sources Vitamin A comes from animal sources, such as eggs, meat, fortified milk, cheese, cream, liver, kidney, cod, and halibut fish oil. However, all of these sources -- except for skim milk that has been fortified with Vitamin A -- are high in saturated fat and cholesterol. Sources of beta-carotene include: • Bright yellow and orange fruits such as cantaloupe, pink grapefruit, and apricots • Vegetables such as carrots, pumpkin, sweet potatoes, and winter squash • Other sources of beta-carotene include broccoli, spinach, and most dark green, leafy vegetables. • The more intense the color of a fruit or vegetable, the higher the beta-carotene content. Vegetable sources of beta-carotene are fat- and cholesterol-free. Effect of Vitamin A If you don't get enough vitamin A, you are more likely to get infectious diseases and vision problems. If you get too much vitamin A, you can become sick. Large doses of vitamin A can also cause birth defects. Acute vitamin A poisoning usually occurs when an adult takes several hundred thousand IUs of vitamin A. Symptoms of chronic vitamin A poisoning may occur in adults who regularly take more than 25,000 IU a day. Babies and children are more sensitive to vitamin A, and can become sick after taking smaller doses of vitamin A or vitamin A-containing products such as retinol (found in skin creams). Large amounts of beta-carotene will not make you sick. However, increased amounts of beta-carotene can turn the skin yellow or orange. The skin color will return to normal once you reduce your intake of beta-carotene. Recommendations The best way to get the daily requirement of essential vitamins is to eat a wide variety of fruits, vegetables, fortified dairy foods, legumes (dried beans), lentils, and whole grains. The Food and Nutrition Board of the Institute of Medicine -- Dietary Reference Intakes (DRIs) Recommended Intakes for Individuals of Vitamin A: Studies on vitamin A 1. The effects of vitamin A compounds on hyaluronic acid released from cultured rabbit corneal epithelial cells and keratocytes. (J Nutr Sci Vitaminol (Tokyo). 2012;58(4):223-9. Toshida H, Tabuchi N, Koike D, Koide M, Sugiyama K, Nakayasu K, Kanai A, Murakami A.) 2. Impact of vitamin A with zinc supplementation on malaria morbidity in Ghana. (Nutr J. 2013 Sep 23;12:131. doi: 10.1186/1475-2891-12-131. Owusu-Agyei S, Newton S, Mahama E, Febir LG, Ali M, Adjei K, Tchum K, Alhassan L, Moleah T, Tanumihardjo SA.) 3. Vitamin A supplementation and serum Th1- and Th2-associated cytokine response in women. (J Am Coll Nutr. 2013;32(4):280-5. doi: 10.1080/07315724.2013.816616. Farhangi MA, Keshavarz SA, Eshraghian M, Ostadrahimi A, Saboor-Yaraghi AA. 4. Improvement of naturally aged skin with vitamin A (retinol). (Kafi R1, Kwak HS, Schumacher WE, Cho S, Hanft VN, Hamilton TA. Arch Dermatol. 2007 May;143(5):606-12.) 5. A randomized trial of vitamin A and vitamin E supplementation for retinitis pigmentosa. (Berson EL1, Rosner B, Sandberg MA, Hayes KC, Nicholson BW. Arch Ophthalmol. 1993 Jun;111(6):761-72.) 6. Vitamin A and risk of bladder cancer: a meta-analysis of epidemiological studies. (Tang JE, Wang RJ, Zhong H, Yu B, Chen Y. World J Surg Oncol. 2014 Apr 29;12(1):130.)

Vitamin A

15.01.12 11:09

Vitamin A

What’s Vitamin A?

Vitamin A is a fat-soluble vitamin.

Two different types of vitamin A are found in the diet. Preformed vitamin A is found in animal products such as meat, fish, poultry and dairy foods. The other type, pro-vitamin A is found in plant-based foods such as fruits and vegetables. The most common type of pro-vitamin A is beta-carotene.

Vitamin A is also available in dietary supplements, usually in the form of retinyl acetate or retinyl palmitate (preformed vitamin A), beta-carotene (pro-vitamin A) or a combination of preformed and pro-vitamin A.

Function of Vitamin A

Vitamin A helps form and maintain healthy skin, teeth, skeletal and soft tissue, mucus membranes, and skin. It is also known as retinol because it produces the pigments in the retina of the eye.

Vitamin A promotes good vision, especially in low light. It may also be needed for reproduction and breast-feeding.

Retinol is an active form of vitamin A. It is found in animal liver, whole milk, and some fortified foods.

Carotenoids are dark-colored dyes (pigments) found in plant foods that can turn into a form of vitamin A. There are more than 500 known carotenoids. One such carotenoid is beta-carotene.

• Beta-carotene is an antioxidant. Antioxidants protect cells from damage caused by substances called free radicals. Free radicals are believed to contribute to certain chronic diseases and play a role in the aging processes.

• Food sources of carotenoids such as beta-carotene may reduce the risk for cancer. Beta-carotene supplements do not seem to reduce cancer risk.

Food Sources

Vitamin A comes from animal sources, such as eggs, meat, fortified milk, cheese, cream, liver, kidney, cod, and halibut fish oil. However, all of these sources -- except for skim milk that has been fortified with Vitamin A -- are high in saturated fat and cholesterol.

Sources of beta-carotene include:

• Bright yellow and orange fruits such as cantaloupe, pink grapefruit, and apricots

• Vegetables such as carrots, pumpkin, sweet potatoes, and winter squash

• Other sources of beta-carotene include broccoli, spinach, and most dark green, leafy vegetables.

• The more intense the color of a fruit or vegetable, the higher the beta-carotene content. Vegetable sources of beta-carotene are fat- and cholesterol-free.

Effect of Vitamin A

If you don't get enough vitamin A, you are more likely to get infectious diseases and vision problems.

If you get too much vitamin A, you can become sick. Large doses of vitamin A can also cause birth defects.

Acute vitamin A poisoning usually occurs when an adult takes several hundred thousand IUs of vitamin A. Symptoms of chronic vitamin A poisoning may occur in adults who regularly take more than 25,000 IU a day. Babies and children are more sensitive to vitamin A, and can become sick after taking smaller doses of vitamin A or vitamin A-containing products such as retinol (found in skin creams).

Large amounts of beta-carotene will not make you sick. However, increased amounts of beta-carotene can turn the skin yellow or orange. The skin color will return to normal once you reduce your intake of beta-carotene.

Recommendations

The best way to get the daily requirement of essential vitamins is to eat a wide variety of fruits, vegetables, fortified dairy foods, legumes (dried beans), lentils, and whole grains.

The Food and Nutrition Board of the Institute of Medicine -- Dietary Reference Intakes (DRIs) Recommended Intakes for Individuals of Vitamin A:

Studies on vitamin A

1. The effects of vitamin A compounds on hyaluronic acid released from cultured rabbit corneal epithelial cells and keratocytes. (J Nutr Sci Vitaminol (Tokyo). 2012;58(4):223-9. Toshida H, Tabuchi N, Koike D, Koide M, Sugiyama K, Nakayasu K, Kanai A, Murakami A.)

2. Impact of vitamin A with zinc supplementation on malaria morbidity in Ghana. (Nutr J. 2013 Sep 23;12:131. doi: 10.1186/1475-2891-12-131. Owusu-Agyei S, Newton S, Mahama E, Febir LG, Ali M, Adjei K, Tchum K, Alhassan L, Moleah T, Tanumihardjo SA.)

3. Vitamin A supplementation and serum Th1- and Th2-associated cytokine response in women. (J Am Coll Nutr. 2013;32(4):280-5. doi: 10.1080/07315724.2013.816616. Farhangi MA, Keshavarz SA, Eshraghian M, Ostadrahimi A, Saboor-Yaraghi AA.

4. Improvement of naturally aged skin with vitamin A (retinol). (Kafi R1, Kwak HS, Schumacher WE, Cho S, Hanft VN, Hamilton TA. Arch Dermatol. 2007 May;143(5):606-12.)

5. A randomized trial of vitamin A and vitamin E supplementation for retinitis pigmentosa. (Berson EL1, Rosner B, Sandberg MA, Hayes KC, Nicholson BW. Arch Ophthalmol. 1993 Jun;111(6):761-72.)

6. Vitamin A and risk of bladder cancer: a meta-analysis of epidemiological studies. (Tang JE, Wang RJ, Zhong H, Yu B, Chen Y. World J Surg Oncol. 2014 Apr 29;12(1):130.)

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