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There are two forms available for vitamin D
維生素D補充劑，有兩種形式
supplements; D2, ergocalciferol and D3,cholecalciferol.
分別是維生素D2和維生素D3
Vitamin D2 is made by the conversion of a sterol
維生素D2由植物和酵母的固醇轉化而來
found in plants and yeast. Vitamin D3 is the form
維生素D3
that is produced naturally in human skin
是人類皮膚暴露在紫外線B光下自然生成的
exposed to ultraviolet B light and occurs
在某些動物產品中也存在，例如魚肝油
in some animal products such as cod liver oil
在多脂魚中也存在少量維生素D3
and in smaller amounts in other fatty fish
例如沙丁魚和金槍魚
such as sardines and tuna. Vitamin D3 is
維生素D3
the most common form used in dietary supplements
在膳食補充劑和牛奶等強化食品中
and fortified foods such as milk. Unlike calcium
是最常見的
these two forms are not equal in absorption.
與鈣不同的是，維生素D3和D2兩種形式的
Vitamin D3 is metabolized differently than D2
吸收效果是不同的，研究表明
and research shows it is more effective in
在提高活性型維生素D的血清濃度方面
raising serum concentrations of the active
D3要比D2更加有效
form of vitamin D and is also able to maintain
而且能夠更加長久地使維生素D保持高水平
high levels for longer. More research is needed
這個領域還需要做更多的研究
in this area but many companies are switching from D2
但是很多企業，將D2的生產轉向D3
to D3 to gain greater benefits from their supplements.
從而在鈣補充劑中獲得更多的利潤
Let's take a minute to understand how to
下面,讓我們了解一下
calculate the amount of vitamin D and calcium
如何通過食物的營養成分標簽
provided in a food from the nutrition label.
計算維生素D和鈣的總量
One serving of cheerios is equal to
一份麥片相當于一杯麥片粥
one cup of cereal. The nutrition label
麥片的營養標簽包括
includes data for cereal alone and for the cereal
麥片單獨的營養數據
with half a cup of skim milk because
也包括麥片與半杯脫脂牛奶共同的營養數據
it is typically consumed with milk. So be sure
因為麥片通常與牛奶一起食用
to understand which column you are reading.
所以一定要弄清楚你看的是哪一列
One serving of cereal alone has 100 calories.
一份麥片有100卡路里的能量
The cereal provides 10% of our
麥片為我們提供了
daily value of calcium. In order to determine
每天所需鈣含量的10%
how many milligrams of calcium that provides
為了弄清楚麥片提供鈣的數量
you need to know that the daily value for calcium
你需要知道人體每日所需要的鈣
is 1000 milligrams. Once you have that information
是1000毫克，有了這個信息后
you can calculate how many milligrams in the serving
用1000乘以0.10或者10%
by multiplying 1000 milligrams by 0.10 or 10%.
你可以計算出每份麥片含有多少鈣
The result is 100 milligrams of calcium
結果是每份麥片提供100毫克的鈣
per serving of cheerios. Similarly a serving
同樣的,一份麥片提供給你
of cheerios provides 10% of your daily value
每日所需鈣含量的10%
of vitamin D. The daily value for vitamin D
每日所需維生素D為400IU
is 400 IU. To calculate the amount in a serving
想計算出每一份麥片提供多少維生素D
multiply 400 by 0.10. The result is 40 IU of
就用400乘以0.10
vitamin D per serving. To find
結果就是每一份提供40IU
a full list of daily values for all nutrients
想找到所有營養物質的每日所需含量
you can go to the FDA website shown
你可以登錄屏幕一邊FDA網址
on the side and search for daily values.
來搜索每日食物攝取量
Vitamin D plays important roles in many processes
維生素D在人體的很多程序上
throughout the body. Probably the most
都發揮著重要作用
well understood function that vitamin D has is in
最為人們所熟知的功能
the absorption of calcium from the small intestine.
就是它幫助小腸吸收鈣
When vitamin D is inadequate calcium from the diet
當維生素D不足的時候
is poorly absorbed. Another well characterized
膳食中的鈣就很難被吸收
and important role of vitamin D is to maintain
維生素另一個特別而重要的作用就是
appropriate levels of calcium and phosphate
保持血液中鈣和磷酸鹽的適當水平
in the blood to ensure proper bone formation,
進而保證正常的骨生成，骨骼礦化
mineralization, growth and repair. Vitamin D
骨生長和骨修復
has other roles that have been less well characterized.
維生素D還有其他不為人所知的作用
