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Our next fat soluble vitamin
下一個要說的脂溶性維生素
is often called the sunshine vitamin: vitamin D.
常被叫做陽光維生素:維生素D
Vitamin D is unique among vitamins
在眾多維生素中,維生素D之所以獨特
because it is produced naturally in the body
是因為陽光照射皮膚時
when skin is exposed to sunlight.
身體能自然地合成維生素D
Sunlight transforms cholesterol
日光將皮膚里存在的膽固醇
which is present in the skin into vitamin D.
轉化為維生素D
Theoretically then anyone exposed to sunlight
所以理論上講,任何一個曬過太陽的人
should have adequate amounts of vitamin D.
體內都應該有充足的維生素D
However this is not the case.
但實際情況并非如此
Recent evidence suggests that most Americans
最新的證據表明大多數美國人
are marginally deficient in vitamin D.
都有輕度缺乏維生素D
This is probably so because most people
這也許是可能因為大多數人
do not receive regular amounts of sun exposure,
沒有接受到正常量的陽光照射
especially during the winter.
尤其是在冬季
The body's ability to produce vitamin D
人體合成維生素D的能力
decreases with age and the use of sun screen
隨年齡增長而降低,而使用防曬霜
also blocks vitamin D synthesis.
也阻止了維生素D的合成
Vitamin D is important in bone health because
維生素D對于骨骼健康很重要
it enhances calcium absorption in the intestine.
因為它能提高腸道對鈣的吸收
Calcium is then the building blocks for bones
而鈣是骨骼生長的基石
so adequate vitamin D is needed to
因此人體需要足夠的維生素D
properly use calcium for bone mineralization.
來促進骨質礦化
Without adequate vitamin D and calcium
如果體內沒有充足的維生素D和鈣
risk of osteoporosis and bone factures can occur.
就有患骨質疏松癥的危險,容易骨折
Recent research also suggests
近期的研究也表明
vitamin D may have a role in immune function,
維生素D可能對免疫系統
cancer prevention and cardiovascular health.
癌癥預防,及心血管健康有一定作用
For the immune system vitamin D may aid
對免疫系統來說,維生素D可能
in the prevention of autoimmune diseases
有助于預防自身免疫病
where the immune system attacks
這種病是由于免疫系統攻擊
the body's own cells
自身的細胞
such as inflammatory bowel syndrome
比如炎癥性腸病
and inflammatory arthritis.
和發炎性關節炎
Vitamin D also aids the immune system
維生素D還通過
by increasing the body's ability to
提高人體消滅致感染微生物的能力
eliminate microbes which can cause infection.
來增強免疫系統的功能
Vitamin D has also been found to have roles
人們還發現維生素D的其他作用
in preventing cell differentiation
那就是防止細胞分化
and decreasing the production of damaged cells
及減少可能發展為癌細胞的
which could develop into cancer cells.
不正常細胞的產生
In this way recent research has suggested
最近的研究顯示
vitamin D may be important
維生素D可能對于
in the prevention of cancer in the breast, prostate,
預防乳腺癌,前列腺癌
stomach, ovary, bladder, esophagus, kidney,
胃癌,卵巢癌,膀胱癌,食道癌,腎癌
lung, pancreas, uterus and other organs.
肺癌,胰腺癌,子宮癌及其他器官的癌癥十分重要
The current recommendation for vitamin D
當前對于50歲以下成年人
for adults under the age of 50 is
推薦的維生素D攝入量
200 to 400 IUs or 5 to 10 micrograms.
為200到400國際單位或5到10微克
However a recent research suggests that
但最近的一項研究表明
these levels may not be adequate.
這個攝入量可能不夠
The National Research Council is currently discussing
美國國家研究委員會正在討論
whether to raise the vitamin D recommendations.
是否提高維生素D的推薦攝入量
Research suggests that recommended intake
研究顯示對于大多數成年人
should be increased to 1300 IUs per day for most adults,
推薦攝入量應該增加到每天1300國際單位
especially those who are older
尤其是對于年紀更大
or live in a colder climate with a long winter season.
或者生活在冬季較長,氣候寒冷環境中的人
There is no evidence that
沒有證據表明
increased intake at this level is harmful.
增加到這一水平的攝入量有害
Good food sources of vitamin D are very limited.
好的維生素D的食物來源很有限
Fish and fish oils are among
魚和魚油是兩種
the most abundant sources of vitamin D.
維生素D含量最充足的食物
Because of the low availability of vitamin D in foods
因為從食物獲得維生素D較少
fortification has been done.
就需要有營養強化
Milk and dairy foods with added vitamin D are
添加了維生素D的牛奶和奶制品是
among the most available sources
最常見的食物來源
as are fortified breakfast cereals.
相同的還有強化早餐谷物
Other sources of vitamin D include
其他維生素D的來源有
eggs but only in the yolk and then beef liver.
雞蛋,不過僅僅是蛋黃,還有牛肝
To ensure adequate vitamin D,
為了確保攝入足量的維生素D
especially in the absence of
尤其是在沒有規律地
regular consumption of dairy foods,
食用奶制品的情況下
a dietary supplement may be recommended.
也建議服用一種膳食補充劑
Look for supplements that contain
找找那些維生素D含量
no more than 200% of the RDA for vitamin D.
不多于推薦日攝入量200%的補品
You may also consider a supplement
你也可以考慮
that contains vitamin D and calcium.
含有維生素D和鈣的補品
These are especially valuable for women
這些對女性尤其有用
because of the bone strengthening effects.
因為有強健骨骼的效果
Once again as reviewed during this presentation
在這里再次回顧一下這堂課
the fat soluble vitamins are vitamin A, vitamin K,
脂溶性維生素有維生素A,維生素K
vitamin E and vitamin D
維生素E和維生素D
