Most people in the United States and Canada get plenty of vitamin D and calcium, and may damage their health by taking too many supplements, experts advised on Tuesday.

While both are important for healthy bones, North Americans may be confused about how much they need, the Institute of Medicine committee said.

Contrary to popular wisdom, many Americans and Canadians get plenty of vitamin D from the sun and do not need extra supplements to keep their bones strong, the expert panel advised.

“National surveys in both the United States and Canada indicate that most people receive enough calcium, with the exception of girls ages 9-18, who often do not take in enough calcium,” the report reads.

“In contrast, postmenopausal women taking supplements may be getting too much calcium, thereby increasing their risk for kidney stones.”

Many foods in North America are fortified with vitamin D and calcium, from milk to breakfast cereal and orange juice. The committee, led by nutritionist Catharine Ross of Pennsylvania State University, looked at a variety of studies.

Most people know that calcium is needed to build and keep bones strong and a few studies have linked low levels of vitamin D to a range of diseases from cancer to multiple sclerosis. The report found there was not enough evidence to make firm conclusions about anything but bones, though.

“We scrutinized the evidence, looking for indications of beneficial effects at all levels of intake. Amounts higher than those specified in this report are not necessary to maintain bone health,” Ross said in a statement.

“Past cases such as hormone replacement therapy and high doses of beta carotene remind us that some therapies that seemed to show promise for treating or preventing health problems ultimately did not work out and even caused harm.”

North Americans need on average 400 International Units (IUs) of vitamin D per day, the committee decided. Those 71 and older may require as much as 800 IUs a day.

The committee set these requirements for calcium:

* Children aged 1 to 3 need 500 milligrams of calcium a day.

* Children 4-8 need 800 milligrams daily.

* Adolescents need more - 1,300 milligrams a day.

* Women 19-50 and men up to 71 require on average 800 milligrams daily.

* Women over 50 and men over 71 need 1,000 mg.

Too much can be dangerous, the committee found.

“Once intakes of vitamin D surpass 4,000 IUs per day, the risk for harm begins to increase. Once intakes surpass 2,000 milligrams per day for calcium, the risk for harm also increases,” the report reads.

“Kidney stones have been associated with taking too much calcium from dietary supplements. Very high levels of vitamin D (above 10,000 IUs per day) are known to cause kidney and tissue damage.”

The American Society for Bone and Mineral Research agreed that there was not yet enough evidence about the benefits of vitamin D and calcium for anything but bone health.

“These new guidelines will help clarify recent misperceptions about the benefits and risks of insufficient or excessive intake,” Dr. Sundeep Khosla, president of the ASBMR and an endocrinologist at the Mayo Clinic in Rochester, Minnesota, said in a statement.

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By Maggie Fox, Health and Science Editor
WASHINGTON