维生素A的英文说明
- 提问者网友：缘字诀
- 2021-05-01 00:20
- 五星知识达人网友：孤老序
- 2021-05-01 01:10
Definition
Vitamin A is a fat-soluble vitamin.
Alternative Names
Retinol; Carotenoids
Function
Vitamin A helps form and maintain healthy teeth, skeletal and soft tissue, mucous 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 need for reproduction and breast feeding.
Retinol is an active type of vitamin A. It is found in animal liver, whole milk, and some fortified foods.
Carotenoids are dark colored dyes found in plant foods that can turn into a form of vitamin A. One such carotenoid is beta-carotene. Beta-carotene is an antioxidant. Antioxidants protect cells from damage caused by unstable substances called free radicals. Free radicals are believed to contribute to certain chronic diseases and play a role in the degenerative processes seen in aging.
Food Sources
Vitamin A comes from animal sources, such as eggs, meat, 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.
Retinol is an active type of vitamin A. It is found in animal liver, whole milk, and some fortified foods.
Sources of beta-carotene are carrots, pumpkin, sweet potatoes, winter squashes, cantaloupe, pink grapefruit, apricots, broccoli, spinach, and most dark green, leafy vegetables. The more intense the color of a fruit or vegetable, the higher the beta-carotene content. These vegetable sources of beta-carotene are free of fat and cholesterol.
Side Effects
If you don't get enough vitamin A, you are more susceptible to 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 IU. 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 and can become sick after taking smaller doses of vitamin A or vitamin A-containing products such as retinol (found in skin creams).
See Hypervitaminosis A.
Increased amounts of beta-carotene can turn the color of skin to yellow or orange. The skin color returns to normal once the increased intake of beta-carotene is reduced.
Recommendations
The best way to get the daily requirement of essential vitamins is to eat a balanced diet that contains a variety of foods from the food guide pyramid.
The Food and Nutrition Board at the Institute of Medicine recommends the following:
Infants
0-6 months: 400 micrograms per day (mcg/day)
7-12 months: 500 mcg/day
Children
1-3 years: 300 mcg/day
4-8 years: 400 mcg/day
9-13 years: 600 mcg/day
Adolescents and Adults
Males age 14 and older: 900 mcg/day
Females age 14 and older: 700 mcg/day
Women who are pregnant or producing breast milk (lactating) need higher amounts. Ask your doctor what dose is best for you.
译文（yujunwu2525译）
定义
维生素A是一种脂溶性维生素。
替代名称
视黄醇，类胡萝卜素
功能
维生素A有助于形成和维持健康的牙齿，骨骼和软组织，粘膜和皮肤。它也被称为维生素A ，因为它生产的色素在视网膜的眼睛。
维生素A促进良好视力，尤其是在光线较暗的情况下。这也可能是需要复制和母乳喂养。
视黄醇是一个积极的类型的维生素A ，发现在动物肝脏，牛奶，酸奶酪和一些强化食品。
类胡萝卜素是黑暗色染料植物食品中发现，可以变成一种形式，维生素A的类胡萝卜素是这样一个β -胡萝卜素。 β -胡萝卜素是一种抗氧化剂。抗氧化剂保护细胞免受损坏所造成的不稳定物质称为自由基。自由基被认为有助于某些慢性疾病和发挥作用的变性过程中出现老化。
食物来源
维生素A来自动物的来源，如鸡蛋，肉类，牛奶，奶酪，奶油，肝脏，肾脏，鳕鱼，大比目鱼和鱼油。然而，所有这些来源-除了脱脂牛奶已强化维生素A -高饱和脂肪和胆固醇。
视黄醇是一个积极的类型的维生素A ，发现在动物肝脏，牛奶，酸奶酪和一些强化食品。
来源的β -胡萝卜素是胡萝卜，南瓜，红薯，冬季瓜类，香瓜，粉红葡萄柚，杏，椰菜，菠菜，和最暗绿色，叶类蔬菜。在更加激烈的颜色的水果或蔬菜，较高的β -胡萝卜素含量。这些蔬菜来源的β -胡萝卜素是免费的脂肪和胆固醇。
副作用
如果你没有得到足够的维生素A ，你更容易受到传染性疾病和视力问题。
如果你摄入过多维生素A，你可能会生病。大剂量维生素A也可导致出生缺陷。急性维生素A中毒通常发生在成年人需要几十万国际单位。成人若经常超过2.5万国际单位/每天，可能会出现慢性维生素A中毒症状，婴儿和儿童容易产生此种情况，往往小剂量的维生素A或维生素A的产品如视黄醇（面霜中含有）就能引起 。
维生素过多综合症：
增加了大量的β -胡萝卜素可以把皮肤的颜色为黄色或橙色。一旦增加摄入β -胡萝卜素是减少了。能皮肤颜色恢复正常。
建议：
最好的方式获得每日所需的维生素是必不可少的均衡饮食，其中包含了各种食品的食物指南金字塔。
美国食品和营养委员会在医学研究所提出以下建议：
婴幼儿
0-6个月： 400微克每天（微克/天）
7-12个月： 500微克/天
孩子们
1-3年： 300微克/天
4-8年： 400微克/天
9-13岁： 600微克/天
青少年和成年人
男性14岁及以上： 900微克/天
女性14岁及以上： 700微克/天
谁是妇女怀孕或生产母乳（哺乳期）需要更高的数额。询问您的医生什么剂量最适合您。