The Institute of Medicine sets its daily vitamin D daily allowance well below the amounts some nutrition experts suggest.

In a Nov. 30 report on dietary reference intakes, IoM sets an estimated average requirement of 400 international units daily for ages 1 year and older in the U.S. and Canada. The recommended dietary allowance is 600 IU other than for people 71 years and older, who should take 800 IU (see chart next page).

IoM also states that "ensuring bone health" remains the only "established function" of vitamin D supported by available research evidence.

"There seems to be little purpose in taking in a higher supplement." – Glenville Jones, IoM committee on vitamin D DRIs

This is the National Academy of Sciences institute's first time recommending a vitamin D estimated average requirement – the level at which 50% of the population's needs are met – and recommended dietary allowance, which reflects the level that 97.5% of the population needs.

IoM established adequate intake and tolerable upper intake levels for vitamin D in 1997. The AI levels varied from 200 IU daily for infants and people up to 50 years old, 400 IU for 51- to 70-year-olds and 600 IU for 71 years and older. The 1997 UI levels were 1,000 IU for infants and 2,000 IU for all other age groups (Also see "“All-Time High” Vitamin D Awareness May Make New DRI Less Relevant – CRN" - Pink Sheet, 1 September, 2008.).

IoM's study of DRIs for calcium and vitamin D began in 2008 following a request from the U.S. and Canadian governments.

Committee members noted during a same-day media briefing that variables in exposure to sunlight for consumers across the two countries had a significant impact on the recommendations.

The recommendations "assume little to no synthesized vitamin D in the individual," said Patsy Brannon, a professor in Cornell University's Division of Nutritional Sciences.

The report sets vitamin D intake upper levels of 1,000 IU daily for infants up to 6 months old, 1,500 IU for 6- to 12-month-olds, 2,500 IU for 1- to 3-year-olds, 3,000 IU for 4- to 8-year-olds and 4,000 for all other age groups.

Competing Recommendations Emerge

While the IoM committee reviewed calcium and vitamin D research data, other experts commented that existing vitamin D intake recommendations were significantly lower than needed.

Committee Chairwoman Catharine Ross, professor of nutrition at Pennsylvania State University, acknowledged those expectations.

"What we have concluded may come as a surprise to some," Ross said.

"We are saying that for a goodly portion of the population it is possible to obtain the calcium and vitamin D at these recommended levels through diet and exposure to sunlight," she added.

Committee member Glenville Jones, head of Queen's University Department of Biochemistry in Ontario, Canada, observed that the recommended levels are to sustain health, not to gain additional benefits.

"So in fact there seems to be little purpose in taking in a higher supplement," Jones said.

A report on the status of vitamin D research in the July 2010 issue of Endocrine Today noted consensus among scientists that the relative daily intake of vitamin D should be increased to 2,000 to 4,000 IU for most adults (Also see "Experts Add To Recommendations For Higher Vitamin D Intake" - Pink Sheet, 26 July, 2010.).

In 2009, the American Academy of Dermatology noted consumers who regularly use sun protection may be at risk for vitamin D insufficiency and may need to supplement their diets. A report presented at the American Association of Clinical Endocrinologists annual Meeting and Clinical Congress recommended between 1,500 and 2,600 IU of vitamin D daily ("AAD recommends higher vitamin D supplementation," "The Tan Sheet" July 20, 2009, In Brief).

A contributor to the Endocrine Today report, Anthony Norman, who has researched vitamin D for nearly 50 years and is a professor emeritus of biochemistry and biomedical sciences at the University of California, Riverside, says the IoM recommendations miss the mark of benefiting public health.

"These new guidelines are conservative," said Norman, who maintained that adults need 2,000 to 4,000 IU of vitamin D daily.

"They've chosen a very conservative approach." – CRN exec Andrew Shao

"A lifetime intake of this safe and ideal dose would prevent borderline vitamin D deficiency, reduce many diseases, increase the longevity and quality of life, and diminish medical care costs worldwide,” he said.

The committee's review found national survey data showed serum 25-hydroxyvitamin D levels in the North American population "generally exceed the levels" the report identifies as sufficient for bone health.

Ross said the committee was aware of concern about deficiencies in vitamin D and calcium levels for people in the U.S. and Canada. However, the committee did not see evidence that such a widespread problem exists, she said.

On the other hand, the committee found data showing potential risks from use of too much vitamin D. This data, which Ross characterized as "emerging, but of concern," influenced the committee to set lower EAR and RDA levels than expected by some.

"We took a cautious approach because we are interested in public health and reducing the risk to the public," she said.

"Overly Conservative"

The Council for Responsible Nutrition says IoM's report is "a modest step in the right direction," but suggests higher intake amounts.

The trade group's senior VP for scientific and regulatory affairs, Andrew Shao, said IoM is "overly conservative," partly due to limits on the research the committee considered in its study.

If the committee expanded its review beyond "the Rolls Royce level of data sets" generated from randomized, controlled clinical trials, numerous observational studies support higher vitamin D intake and show potential health benefits in addition to bone strength, Shao said.

"It's really 'what philosophical approach to take here and what to do with the data that are available?' They've chosen a very conservative approach," he said.

The report states that "despite the many claims of benefit … the evidence did not support a basis for a causal relationship between vitamin D and many of the numerous health outcomes purported to be affected by vitamin D intake," such as helping prevent some cancers.

"There's a lack of evidence of cause and effect," said Brannon. "We're still needing more research," she added.

Jones acknowledged that observational studies "pointed to vitamin D having a positive effect" beyond bone strength but do not establish causality.

"It isn't nearly as clear-cut as some of the advocates would suggest," he added.

The committee's choice of evidence to review reflects one side of an ongoing disagreement over health claim decisions between supplement industry stakeholders and government agencies and other entities. While the industry promotes including observational studies in evidence for health claims, FDA and IoM consider only RCTs appropriate.

However, the industry expects some help toward having supplement health claims approved from the National Center for Complementary and Alternative Medicine's draft strategic plan. The recently released draft emphasizes funding more preliminary research needed to launch informative clinical trials on supplement ingredients.

Meanwhile, stakeholders say it is unfair to maintain that RCT results invalidate conflicting information from observational studies on the effects of nutrients.

"The majority of the research that they have to rely on is not conducted with DRI questions in mind," Shao said.

"What the IoM wants for its recommendations can't be achieved. So what they do is they make very conservative recommendations," he added.

Further, he maintained, the committee's concern about possible risk from higher vitamin D levels appears unsupported by the evidence.

"You can speculate to no end that there might be some kind of harm done to someone somewhere down the line. No matter what kind of data set you have in front of you, you can always speculate that."

Open To Additional Evidence

IoM should consider evidence from research showing additional health benefits from calcium and vitamin D, Ross said.

"We're not saying that we're not interested in other indicators. We're saying that the data are not sufficient at present to use this information or to conclude that intakes higher than those recommended in this report would be beneficial," she said.

Committee member Steven Clinton, a medical oncology professor at Ohio State University's Department of Internal Medicine, commented that there is no lack of research literature on additional benefits from vitamin D. But there is little good data, he added.

"We're really going to need to do an immense amount of research to enhance our knowledge of how each of these nutrients affect cancer," Clinton said.

Clinton also pointed out that based on the committee's finding that most people have sufficient vitamin D levels, testing for the nutrient "probably should not be part of routine medical care." Instead, physicians should consider whether an individual patient may have an insufficient level.

CRN acknowledges the IOM committee had to consider significant variables, notably the amount of exposure consumers have to the sun and in the analytical methods used to determine the amount of vitamin D in the population.

"You're never going to have certainty. That's not achievable when you're talking about these things," Shao said.

By Malcolm Spicer

IoM Sets Vitamin D Intake Levels Below Experts' Expectations

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