Taking about three times as much vitamin D as the norm may lower an individual's risk of developing colon, breast or ovarian cancer, a study says.
Americans typically take 320 units a day of the vitamin，consisting of 200 from food and 120 from supplements. Daily intake of about 1 ， 000 units may cut the odds of getting colon cancer by about half,and the chances of getting breast or ovarian cancer by about a third, ac?cording to the researchers.
Vitamin D supplementation could reduce cancer incidence " at low cost，with few or no side effects”，the researchers said in an article appearing in the February 2006 issue of the American Journal of Public Health.
"The strongest effect is for colorectal cancer,”said lead author Cedric Garland, 59, a pro?fessor of family and preventive medicine at University of California-San Diego, in a telephone interview Tuesday. Garland said.
The U. S. National Academy of Sciences recommends daily vitamin D intake of at least 200 units for adults 50 or younger; 400 units at ages 51 to 70 ，and 600 units for people 71 or older. The upper limit for safe intake is 2， 000 units daily. Thus,the dose recommended by the re?searchers is beyond what most people now get and what the government recommends.
A glass of milk contains about 100 units of the vitamin, Garland said. While cod liver oil is rich in vitamin D，it also contains a lot of vitamin A and the two vitamins compete for reception by the body,Garland said. He doesn't recommend cod liver oil as a source of vitamin D.
To ensure getting 1 ， 000 units of vitamin D, most people probably can take two 400-unit tablets，with the other 200 units coming from foods such as salmon，orange juice，yogurt and cheese, Garland said. Getting enough vitamin D through supplements would cost less than 5 cents a day，he said.
Although sunlight helps the body produce natural vitamin D，the researchers urged getting the minimum of 1， 000 units through food and supplements. Dark-skinned people, who need more sunlight to make vitamin D.are at increased risk of vitamin D deficiency，the scientists said.
( ) 1. What is the subject discussed in the text?
A.How to take Vitamin D in daily life.
B.Scientists urge a bigger dose of Vitamin D.
C.The connection between Vitamin D and cancers.
D.The recommended units of Vitamin D.
( ) 2. According to the text,what is the best way to take Vitamin D?
A. By enjoying the sunlight.
B.Through daily food.
C.By taking some pills every day.
D.From food and daily supplements.
( ) 3. Why is cod liver oil not recommended as a source of Vitamin D?
A.It doesn't contain a lot of Vitamin D.
B.Some people may take in Vitamin A more from it.
C.Although it is rich in Vitamin D.it's hard for people to take it in.
D.It has some unexpected side effects.
( ) 4. Which of the following statements is true according to the passage?
A.People can take as much Vitamin D as they can.
B.Generally, older people need more Vitamin D than the younger.
C.Taking Vitamin D can be very expensive.
D.People of the same age need the same amount of Vitamin D.
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