How much vitamin D, calcium is right?

(CNN) -- Vitamin D and calcium have long been touted as the best nutrients for strong bones, muscles and teeth. Recent studies have shown that vitamin D could be used to fight cancer, heart ailments, autoimmune diseases, even diabetes.

But too much vitamin D can damage the kidneys and the heart. So what's the right balance?

After reviewing nearly 1,000 published studies on vitamin D and calcium, the Institute of Medicine on Tuesday recommended that most Americans and Canadians up to age 70, who are not pregnant, need no more than 600 international units (IUs) of vitamin D per day to maintain good health. People over age 70 may need as much as 800 IUs.

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A three-ounce serving of canned tuna contains about 200 IUs, the standard unit for vitamin D and many other nutrients.

The Institute of Medicine, an independent nonprofit agency, serves as an adviser to the U.S. government to improve health.

The agency's calcium recommendations vary based on age and pregnancy, and range from 700 to 1,300 milligrams per day. One cup of whole milk, for instance, contains around 300 milligrams of calcium.

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"When making these recommendations, we took into account the study data, looking at national surveys of blood levels," said Catharine Ross, professor of nutritional sciences, Penn State University, University Park, and chairman of the committee that set the recommendations.
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"The blood levels indicate how much vitamin D you have in your blood, based on the amount of sunlight you are exposed to, how much vitamin D and calcium you have in your diet, and what type of supplements you are taking."

The committee surprisingly found the majority of Americans and Canadians are getting enough vitamin D and calcium. Some adolescent girls may not get quite enough calcium, and some elderly may fall short of the necessary amounts of calcium and vitamin D. These individuals should increase their intake of foods containing these nutrients.

Sunlight is the best source of vitamin D, but not everyone receives the same exposure. According to the intitute, the new guidelines for vitamin D cover the needs of individuals who get little sun.

The minimum recommended amount of daily sunlight depends on your skin pigmentation. White people should get not less than 5 minutes without sunscreen. People of color should get 15 to 20 minutes. There is no recommended maximum.

Nutritionists recommend getting the rest of your vitamin D and calcium through foods, such as oily fish (salmon, tuna), milk, mushrooms, egg yolks and fortified cereal.

Daily supplements are also helpful, but experts advise people to pay attention to how much they're taking. Because people are becoming more aware of their diets and more individuals are taking supplements, the chance is higher that people may consume too much of these nutrients. Getting too much vitamin D can be dangerous and has been associated with kidney stones as well as damage to the kidneys and the heart.

"No one can overdose from sun exposure because of the way the body processes it. And too much of these nutrients in your diet is highly unlikely," noted Ross. "People can take too many supplements. That's why we made these recommendations."

Ross also noted that while the report found most of the data confirmed that calcium and vitamin D do play a huge role in skeletal growth and keeping up good bone health, they could not find strong evidence that vitamin D protected the body against cancer, heart disease, autoimmune diseases and diabetes.

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"While we found these studies point to the need for further investigation on the role of vitamin D and these illnesses, " said Ross, "we found conflicting and actually mixed results in these studies on the effects of vitamin D on these conditions."

Katherine Tallmadge, spokesperson for the American Dietetic Association supports the call for more research.

"In its most recent recommendation, the [Institute of Medicine] has established the level they believe will protect bones," Tallmadge said. "More studies need to be conducted to validate if we need to recommend higher levels of vitamin D supplementation or higher levels in the blood for protection of other diseases which have recently come to light."

For now, Ross said she believes the guidelines are the best way for people to get the most out of vitamin D and calcium without causing problems.

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