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All cells of the body use vitamin A
身體內(nèi)所有細胞都利用維生素A
to regulate these events. Vitamin A helps
調(diào)節(jié)這些活動,維生素A還幫助
to form skin and mucus membranes and keeps them healthy.
形成皮膚和粘膜,并使它們保持健康
Skin and mucus membranes are important
皮膚及粘膜對于
in helping our bodies avoid infections
幫助我們身體抵御感染十分重要
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
類胡蘿卜素是一種在果蔬中的深色染料
that can turn into a form of vitamin A.
它可以轉(zhuǎn)變成一種維生素A
One carotenoid is beta carotene
有一種類胡蘿卜素叫β-胡蘿卜素
which is an antioxidant which protects cells from damage
它是一種抗氧化劑,能保護細胞免于傷害
and oxidative stress and
和氧化
therefore helps with decreasing the risk of cancer.
因此它能幫助降低患癌癥的幾率
Vitamin A also plays a role
維生素A也在調(diào)節(jié)
in the regulation of the immune system.
免疫系統(tǒng)中發(fā)揮著作用
It may help in the development of a certain type of
它可以促進一種
white blood cell called lymphocytes which are essential
叫淋巴球的白細胞的形成
in fighting infections from viruses and bacteria.
淋巴球?qū)τ诘钟《竞图毦腥居惺种匾?/div>
Vitamin A also maintains the cell
維生素A也能維護
that keeps up the membrane associated with the eyes
眼睛
and respiratory, urinary and intestinal tracts.
及呼吸道,尿道,腸道的膜上的細胞
When vitamin A is deficient these cells become damaged
缺乏維生素A時,這些細胞就遭到破壞
resulting in leaks in the membranes
發(fā)生細胞膜滲漏
through which bacteria can then enter and cause infection.
細菌便會通過細胞膜進入導(dǎo)致感染
The units of vitamin A that you will see reported include
你們會看到,維生素A的單位包括
both micrograms and international units or IUs.
微克和國際單位,簡稱IU
IUs are used because foods contain compounds
使用國際單位是因為食物中含有
that can be converted to vitamin A in the body.
可以在人體內(nèi)轉(zhuǎn)化為維生素A的成分
Beta carotene is the most abundant of these compounds.
β-胡蘿卜素,是這些成分中最多的
About one third of the beta carotene
我們攝入的β-胡蘿卜素約有三分之一
that we consume from foods is converted to vitamin A
會被轉(zhuǎn)化為維生素A
therefore IUs take into account the ability
因此使用國際單位能
of the human body to use these sources of vitamin A.
將人類身體利用這些維生素A來源的能力考慮進來
The daily recommended intakes for vitamin A
19歲以上成年男子
for adult males, 19 years of age and above,
每日推薦的維生素A攝入量
are 3000 IUs or 900 micrograms. For women
為3000個國際單位或900微克,女性所需的
the intake is lower, 2310 IUs or 700 micrograms.
攝入量少些,為2310個國際單位或700微克
Pregnant and lactating women have increased needs:
懷孕的和哺乳期的女性需要更多:
2565 IUs or 770 micrograms for pregnant women
孕婦需要2565單位或770毫克
and 4300 IUs or 1300 micrograms for lactating women.
毫克,哺乳期女性需要4300國際單位或1300微克
Here's a list of good food sources for vitamin A.
這里列出了含有維生素A的優(yōu)質(zhì)食物來源
Green leafy vegetables and brightly colored orange
綠葉蔬菜和顏色鮮亮的橙子
and yellow vegetables are easy to remember
以及黃色的蔬菜是很容易記住的
as excellent sources of vitamin A.
絕好的維生素A來源
A sweet potato baked in its skin contains 24877 IUs
一個帶皮的烤紅薯含有24877國際單位
of vitamin A, mostly in the form of beta carotene.
的維生素A,其中大多是β-胡蘿卜素
Even though this seems like a large amount of vitamin A
盡管這看起來是很大量的維生素A
there is no evidence that food sources of vitamin A
但是沒有證據(jù)表明含維生素A的食物
can produce toxicity.
會產(chǎn)生毒性
As mentioned the body converts only a small amount
像之前說的,人體僅將很少量的
of beta carotene to the vitamin.
β-胡蘿卜素轉(zhuǎn)化成維生素
Here's some more food sources of vitamin A.
這里還有更多的一些含維生素A的食物
As you can see green leafy vegetables
你可以看到,綠葉菜是維生素A的
are excellent sources of vitamin A.
絕佳食物來源
Look for really dark green vegetables such as spinach
看看深綠色蔬菜,比如菠菜
which contains about 7370 IUs of vitamin A
含有大約7370國際單位的維生素A
which makes up 150% of
這相當(dāng)于每日推薦
the total daily recommended intake.
攝入總量的150%
Beef liver is also an excellent source of vitamin A
牛肝也是一種絕好的維生素A的食物來源
which contains 27185 IUs of vitamin A
含有27185國際單位的維生素A
or 545% of the total daily recommended intake.
相當(dāng)于每日推薦攝入量的545%
Egg yolks and fortified egg substitutes
蛋黃和強化的雞蛋替代品
are also sources of vitamin A
也含有維生素A
although not as high as liver
盡管其含量沒有肝臟
and green leafy vegetables.
和綠葉菜所含的多
When using supplements be cautious of any that
在使用補品的時候,要謹慎選擇
contain more than 200% of the RDA for vitamin A.
任何含有超過200%每日推薦維生素A攝入量的補品
As mentioned vitamin A is stored in the body
之前提到過,維生素A會被貯存在體內(nèi)
and can be toxic.
并且會產(chǎn)生毒性
