While many people aren't getting enough calcium,new research cautions that some people may have the opposite problem：They could be getting too much.Americans spend more than﹩1 billion a year on calcium supplements in hopes of delaying osteoporosis,the brittle bone disease that cripples many elderly women and some men.Yet recent studies link calcium supplements to a higher risk of heart attacks.Last month,the U.S.Preventive Services Task Force issued a draft recommendation against taking calcium and vitamin D，saying there wasn't enough evidence of benefit to justify the risk.
For generations of Americans who grew up encouraged to drink milk to maintain strong bones,the reports raised troubling questions：Is calcium not so important after all？Are the supplements unsafe？And how much is too much？ "It's gotten very confusing but it doesn't need to be," says Ethel Siris,director of the Toni Stabile Osteoporosis Center in New York.How much calcium people need varies by age and gender. "Adults generally need 1，000 mg daily,rising to 1，200 mg for women over 50 and men over 70，according to guidelines issued in 2010.Children need 1，300 mg daily during the peak growing years of 9 to 18."
People also need sufficient levels of vitamin D to absorb the calcium.The IOM recommends 600 international units a day for most adults,and 800 daily after age 70，although many physicians recommend more.It is difficult to take in that much vitamin D from food sources,so experts say many people should take vitamin D in supplement form.
Getting adequate calcium from food is easier.For example,8 ounces of milk or 6 ounces of yogurt has 300 mg of calcium,and one cup of spinach has 270 mg.
But studies linking calcium supplements to heart attack have made experts more cautious of excess calcium than before.A study of 24，000 Germans published in the journal Heart last month,found that those who got their calcium exclusively from supplements were more than twice as likely to have a heart attack as those who took no supplements.
Exactly how calcium supplements might contribute to heart attacks baffles cardiologists. "Nobody has associated the calcium in your bloodstream with calcification in your arteries," says Nieca Goldberg,medical director of the Joan H.Tisch Center.Still,she says she now urges patients get their recommended calcium from food than from supplements to avoid possible problems.
Osteoporosis experts also urge patients not to take more than the recommended amount of calcium. "People should definitely stop taking two big calcium supplements a day," says Dr.Dawson-Hughes.Even if the risks remain unclear,taking more than the body can absorb doesn't benefit bones,"so it's not worth any risk." She adds.



According to the new studies,taking much calcium might ______ .

A. delay aging
B. build muscles
C. cause heart problems
D. cure bone diseases

What is Ethel Siris' opinion on taking calcium supplements？ ______

A. Taking calcium supplements is unsafe.
B. Adults need more calcium than children.
C. Age and gender determine taking calcium.
D. It is much safer to take calcium from food.

What does the underlined word "baffle" in Paragraph 6 mean？ ______

A. Interest.
B. Puzzle.
C. Amaze.
D. Frighten.

What can we learn from the passage？ ______

A. It is helpful to take two calcium supplements a day.
B. It is important to maintain strong bones for women.
C. It is unnecessary to take too much calcium supplement.
D. It is best to take calcium and vitamin D from supplement.