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All cells of the body use vitamin A
身体内所有细胞都利用维生素A
to regulate these events. Vitamin A helps
调节这些活动,维生素A还帮助
to form skin and mucus membranes and keeps them healthy.
形成皮肤和粘膜,并使它们保持健康
Skin and mucus membranes are important
皮肤及粘膜对于
in helping our bodies avoid infections
帮助我们身体抵御感染十分重要
and are found all over our bodies: eyes, mouth,
而且遍布全身:眼睛,口腔
respiratory tract, urinary tract and alimentary tract.
呼吸道,尿道,以及消化道
Carotenoids are dark colored dyes found in plant foods
类胡萝卜素是一种在果蔬中的深色染料
that can turn into a form of vitamin A.
它可以转变成一种维生素A
One carotenoid is beta carotene
有一种类胡萝卜素叫β-胡萝卜素
which is an antioxidant which protects cells from damage
它是一种抗氧化剂,能保护细胞免于伤害
and oxidative stress and
和氧化
therefore helps with decreasing the risk of cancer.
因此它能帮助降低患癌症的几率
Vitamin A also plays a role
维生素A也在调节
in the regulation of the immune system.
免疫系统中发挥着作用
It may help in the development of a certain type of
它可以促进一种
white blood cell called lymphocytes which are essential
叫淋巴球的白细胞的形成
in fighting infections from viruses and bacteria.
淋巴球对于抵御病毒和细菌感染有十分重要
Vitamin A also maintains the cell
维生素A也能维护
that keeps up the membrane associated with the eyes
眼睛
and respiratory, urinary and intestinal tracts.
及呼吸道,尿道,肠道的膜上的细胞
When vitamin A is deficient these cells become damaged
缺乏维生素A时,这些细胞就遭到破坏
resulting in leaks in the membranes
发生细胞膜渗漏
through which bacteria can then enter and cause infection.
细菌便会通过细胞膜进入导致感染
The units of vitamin A that you will see reported include
你们会看到,维生素A的单位包括
both micrograms and international units or IUs.
微克和国际单位,简称IU
IUs are used because foods contain compounds
使用国际单位是因为食物中含有
that can be converted to vitamin A in the body.
可以在人体内转化为维生素A的成分
Beta carotene is the most abundant of these compounds.
β-胡萝卜素,是这些成分中最多的
About one third of the beta carotene
我们摄入的β-胡萝卜素约有三分之一
that we consume from foods is converted to vitamin A
会被转化为维生素A
therefore IUs take into account the ability
因此使用国际单位能
of the human body to use these sources of vitamin A.
将人类身体利用这些维生素A来源的能力考虑进来
The daily recommended intakes for vitamin A
19岁以上成年男子
for adult males, 19 years of age and above,
每日推荐的维生素A摄入量
are 3000 IUs or 900 micrograms. For women
为3000个国际单位或900微克,女性所需的
the intake is lower, 2310 IUs or 700 micrograms.
摄入量少些,为2310个国际单位或700微克
Pregnant and lactating women have increased needs:
怀孕的和哺乳期的女性需要更多:
2565 IUs or 770 micrograms for pregnant women
孕妇需要2565单位或770毫克
and 4300 IUs or 1300 micrograms for lactating women.
毫克,哺乳期女性需要4300国际单位或1300微克
Here's a list of good food sources for vitamin A.
这里列出了含有维生素A的优质食物来源
Green leafy vegetables and brightly colored orange
绿叶蔬菜和颜色鲜亮的橙子
and yellow vegetables are easy to remember
以及黄色的蔬菜是很容易记住的
as excellent sources of vitamin A.
绝好的维生素A来源
A sweet potato baked in its skin contains 24877 IUs
一个带皮的烤红薯含有24877国际单位
of vitamin A, mostly in the form of beta carotene.
的维生素A,其中大多是β-胡萝卜素
Even though this seems like a large amount of vitamin A
尽管这看起来是很大量的维生素A
there is no evidence that food sources of vitamin A
但是没有证据表明含维生素A的食物
can produce toxicity.
会产生毒性
As mentioned the body converts only a small amount
像之前说的,人体仅将很少量的
of beta carotene to the vitamin.
β-胡萝卜素转化成维生素
Here's some more food sources of vitamin A.
这里还有更多的一些含维生素A的食物
As you can see green leafy vegetables
你可以看到,绿叶菜是维生素A的
are excellent sources of vitamin A.
绝佳食物来源
Look for really dark green vegetables such as spinach
看看深绿色蔬菜,比如菠菜
which contains about 7370 IUs of vitamin A
含有大约7370国际单位的维生素A
which makes up 150% of
这相当于每日推荐
the total daily recommended intake.
摄入总量的150%
Beef liver is also an excellent source of vitamin A
牛肝也是一种绝好的维生素A的食物来源
which contains 27185 IUs of vitamin A
含有27185国际单位的维生素A
or 545% of the total daily recommended intake.
相当于每日推荐摄入量的545%
Egg yolks and fortified egg substitutes
蛋黄和强化的鸡蛋替代品
are also sources of vitamin A
也含有维生素A
although not as high as liver
尽管其含量没有肝脏
and green leafy vegetables.
和绿叶菜所含的多
When using supplements be cautious of any that
在使用补品的时候,要谨慎选择
contain more than 200% of the RDA for vitamin A.
任何含有超过200%每日推荐维生素A摄入量的补品
As mentioned vitamin A is stored in the body
之前提到过,维生素A会被贮存在体内
and can be toxic.
并且会产生毒性
