Rethinking Healthcare

You don't need more calcium and vitamin D

You don't need more calcium and vitamin D

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A panel of scientists found that most people in North America get enough calcium and vitamin D from their normal diet and that too much from supplements could be harmful.

Most people get enough and more is not better, a new report shows.

After spending two years developing new guidelines for these nutrients and sifting through a thousand studies, the Institute of Medicine released a report yesterday detailing new, increased intake levels. But it also reassures us that “the majority of Americans and Canadians are getting enough vitamin D and calcium.”

We all know calcium is necessary for healthy teeth and bones. My milk carton always reminds me that, in order to be absorbed by the body, calcium needs vitamin D – or the “sunshine vitamin” because sunlight triggers its natural production in skin.

The new ‘Dietary Reference Intakes for vitamin D (which even cover the needs of people who get little sun) are:

- 600 international units (IUs) per day for people up to 70 years old,
- 800 IUs for those 71 and older.

The 1997 ‘Adequate Intakes’ – or “guesstimate” as panelist Patsy Brannon of Cornell University called them – were:

- 200 IU/day for infants through age 50,
- 400 IU/day for ages 51 to 70,
- 600 IU/day for those 71 and older.

The new calcium recommendations haven’t changed as much and still ranges between 700 and 1,300 milligrams per day, depending on age.

- Adults 19 through 50 (and men until 71) need just 1,000 milligrams of calcium per day.
- Women starting at age 51 and everyone age 71 and older need no more than 1,200 milligrams per day.

According to Pennsylvania State University nutritional scientist Catharine Ross who chaired the committee of 14 scientists, amounts higher than those specified in this report are not necessary to maintain bone health.

Good thing too because national surveys of blood levels show that “most people will eat enough diverse range of foods to achieve the recommended allowance,” said panelist Steven Clinton of Ohio State University.

That is, except adolescent girls, who should increase their intake of foods with these nutrients or take supplements.

An 8 oz. glass of milk in the US generally has about 300 mg of calcium and is fortified with 100 IU of vitamin D. The vitamin is naturally found in fatty fish like salmon and also egg yolk, and it's added to some breakfast cereals, orange juice, yogurt, margarine, and soy beverages. And if your diet lacks enough vitamin D, the sun provides enough to make up the difference (except maybe during the winter in the northern half of the US).

Confusions and contradictions

The findings clearly contradict earlier studies that showed how vitamin D deficiency was rampant in the US.

According to the report, the measurements of sufficiency and deficiency that labs have used weren’t based on rigorous scientific studies and are not standardized. The lack of agreement means the same individual could be declared deficient depending on the lab that reads the test, resulting in an overestimation of vitamin D deficiency. (The committee found that almost all individuals get sufficient vitamin D when their blood levels are at or above 20 nanograms per milliliter.)

The panel did note how its findings challenged the notion that, with dietary nutrients, “more is better.”

That belief inspired a multibillion-dollar market for dietary supplements. Americans spent $1.2 billion last year on calcium supplements and $430 million on pills containing vitamin D, which soared from $40 million in 2001. And doctors have added blood tests of vitamin D levels to annual physicals.

Many studies have lauded vitamin D as therapeutic for everything from fighting infections to protecting against cancer, heart disease, and diabetes. And as each emerged, advocates have recommended amounts of 2,000 IU/day, and many supplements are now sold in doses of 1,000 IUs.

But the report suggests that many of these studies conflict and there’s no evidence that vitamin D has these beneficial effects. “What we have are intriguing other areas that warrant research,” Clinton said. “Yet the data at the moment is insufficient with regards to defining an appropriate intake. Bone health is the primary outcome.”

In fact, the committee warns that too much calcium from dietary supplements has been associated with kidney stones, while excessive vitamin D can damage the kidneys and heart.

Michael Holick of Boston University is a leading proponent of high doses and maintains that most people need at least 3,000 IU/day. That's what he takes, and what he recommends to his patients. “My recommendation is very simple,” he said. “When I've been recommending for the past decade that people take more than the [officially recommended] 200 units, there was a lot of skepticism. Now they're recommending three times what we recommended in 1997”.

But according to Ross, the new recommendations will “have a shelf life of many years” in terms of setting health recommendations – influencing everything from nutritional labeling to school lunch composition.

And here are the new upper limits for adults (which you should not strive for, as the report reminds):

- Vitamin D: 4,000 IU/day for everyone 9 and above. (This is upped from the old maximum of 2,000.)
- Calcium: 2,500 mg/day from age 19 through 50, and 2,000 mg/day for everyone older.

Image: Vitamins by stemcellbiotherapy via Flickr

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Janet Fang

Contributing Editor

Janet Fang has written for Nature, Discover and the Point Reyes Light. She is currently a lab technician at Lamont-Doherty Earth Observatory. She holds degrees from the University of California, Berkeley and Columbia University. She is based in New York. Follow her on Twitter. Disclosure