IOM Says No Need to Megadose Vitamin D - IOM Brief Report below with pdf attached
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Published: November 30, 2010
Concerns about vitamin D and/or calcium deficiency may be misplaced while claims about the health benefits of vitamin D may be overblown, according to the latest report from the Institute of Medicine.
The IOM report concluded that most Americans don't need megadoses of vitamin D or calcium to maintain healthy bones, and healthy bones are all that the nutrients can guarantee.
The IOM reviewed more than 1,000 studies and consulted numerous nutrition and public health experts to come to that conclusion.
"Despite the many claims of benefit surrounding vitamin D in particular, 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," the report stated.
* Explain that most Americans and Canadians consume adequate calcium and vitamin D to support bone health, according to an IOM report.
* Explain that the report did not find a causal relationship for vitamin D in prevention of cancer and cardiovascular disease, or in immune function.
The IOM's findings are unlikely to be the final word on vitamin D, however, especially since the immediate reaction to the report was highly mixed.
Jana Klauer, MD, a research fellow at St. Luke's Roosevelt Hospital in New York City who also has a private practice as a weight-loss expert, was blunt in her condemnation, telling ABC News/MedPage Today that she did "not agree with the report and am somewhat dismayed at their conclusions."
Equally blunt was the assessment offered by Darrell Rigel, MD, a New York City dermatologist and a past president of the American Academy of Dermatology, who told ABC News/MedPage Today that he was pleased with the repot.
Rigel said that much of the recent concern about the risk of vitamin D deficiency is fueled by a lack of a standard definition.
"If I told you that water freezes at 50 degrees instead of 32 degrees, I will still have a lot of cold water, but no ice. If you set the definition of vitamin D deficiency lower you will find more people who are "deficient" but this doesn't have clinical meaning," he said.
Nortin M. Hadler, MD, of the University of North Carolina at Chapel Hill, and a vocal critic of medical fads, said that while the IOM report provided enough solid evidence to be a "last word" on vitamin D, he doubted that would be case because "there is so much hype and misinformation" that the vitamin D "debate" is likely to drag on.
"The 'medicalization' of 'osteopenia' is a plague on our women. It is driven by the ubiquity of the [bone mineral density] measurement and the aggressive marketing of agents that increase BMD," Hadler said. "The 'medicalization' of vitamin D levels has become a handmaiden."
Because the IOM could not find evidence to support extraskeletal benefit for vitamin D or calcium, the authors of the report decided to base daily intake recommendations on the amount needed for the maintenance of bone health.
For calcium, they reported that children ages 1 to 3 need about 500 mg each day, and those between 4 and 8 have an average requirement of 800 mg a day.
The requirement rises to 1,300 mg a day for adolescents, who experience growth spurts and enhanced bone growth, and falls back to 800 mg each day for adults up to the age of 70.
Women between 50 and 70 are exceptions; they should be receiving 1,000 mg of calcium a day, as should all adults 71 and older.
Although most people do consume adequate calcium, a notable exception is teenage girls, the IOM authors pointed out.
Establishing proper intake levels for vitamin D was more complex, the report noted, because the source of this nutrient is not only the diet, but also sunlight, which can vary considerably depending on multiple factors including skin color and sunscreen use.
Nonetheless, the IOM committee determined that the majority of people need about 400 IU of vitamin D daily, although those 71 and older may require up to 800 a day.
They found that the usual dietary intake of vitamin D was below the median recommended. Regardless of this dietary deficit, actual measurement of blood levels of the vitamin found levels that typically exceed 20 ng/mL -- the level required for bone health -- with the shortfall being made up by sun exposure.
Because of the popularity of dietary supplements that can contain very high levels of the nutrients, the report also addressed the upper levels that can be considered acceptable, and beyond which risks begin to emerge.
"There is controversy concerning levels of nutrient intake, and at times the concept that 'more is better' emerges," the report stated.
"However, for both calcium and vitamin D, there is another underlying question: How much is too much?" the authors wrote.
For people in most age groups, the upper level of intake for calcium ranged from 2,000 mg to 3,000 mg per day, while for vitamin D the upper level for all adolescents and adults was 4,000 IU daily.
Harley Haynes, MD, of Brigham and Women's Hospital and a professor at Harvard, disagreed with this recommendation.
Haynes said that geography needs to be factored into the recommendations noting that he thinks, "the IOM's recommendations for replacement are too low to get patients at the latitude of Boston into the top or next-to-top quartile of the normal range."
In his practice, he recommends "2,000 to 4,000 IU daily of D3, the higher amount for people who are seriously protected from sun by having minimal daytime outdoor exposure, or using careful sunscreen and protective clothing, or who are very darkly pigmented. I try to get their level into the highest quartile of the normal range. For persons getting significant unprotected sun exposure, I recommend only 400 to 800 IU daily except in October to April in this latitude, when sun exposure is insufficient to produce even 400 IU vitamin D daily, during which time I recommend a larger amount."
According to the IOM, potential hazards of high-level calcium supplementation included an increased risk for kidney stones and possibly for cardiovascular disease.
And very high levels of vitamin D supplementation, in excess of 10,000 IU per day, have been associated with damage to the kidneys and other tissues.
The report also explored whether the dietary needs differed for certain segments of the population, such as those with dark skin.
The authors acknowledged that there may be concerns for these groups but were unable to provide many firm recommendations because of the many possible contributors such as ethnic dietary and cultural practices.
They did note, however, that infants who are exclusively breast fed, particularly those who are dark skinned, should have vitamin D dietary supplementation of about 400 IU daily, because breast milk does not contain the vitamin.
The institutionalized elderly also may have inadequate exposure to sunlight, so monitoring of their nutrition should include attention to levels of both calcium and vitamin D.
The study was supported by the U.S. Department of Agriculture, the Department of the Army, the U.S. Department of Health and Human Services, the National Institutes of Health, and Health Canada.
Dietary Reference Intakes for Calcium and Vitamin D - pdf of this brief report attached
November 30, 2010
Dietary Reference Intakes for Calcium and Vitamin D
Calcium and vitamin D are two essential nutrients long known for their role in bone health. Over the last ten years, the public has heard conflicting messages about other benefits of these nutrients-especially vitamin D-and also about how much calcium and vitamin D they need to be healthy.
To help clarify this issue, the U. S. and Canadian governments asked the Institute of Medicine (IOM) to assess the current data on health outcomes associated with calcium and vitamin D. The IOM tasked a committee of experts with reviewing the evidence, as well as updating the nutrient reference values, known as Dietary Reference Intakes (DRIs). These values are used widely by government agencies, for example, in setting standards for school meals or specifying the nutrition label on foods. Over time, they have come to be used by health professionals to counsel individuals about dietary intake.
The committee provided an exhaustive review of studies on potential health outcomes and found that the evidence supported a role for these nutrients in bone health but not in other health conditions. Overall, the committee concludes that the majority of Americans and Canadians are receiving adequate amounts of both calcium and vitamin D. Further, there is emerging evidence that too much of these nutrients may be harmful.
Health Effects of Vitamin D and Calcium Intake
The new reference values are based on much more information and higher-quality studies than were available when the values for these nutrients were first set in 1997. The committee assessed more than one thousand studies and reports and listened to testimony from scientists and stakeholders before making its conclusions. It reviewed a range of health outcomes, including but not limited to cancer, cardiovascular disease and hypertension, diabetes and metabolic syndrome, falls, immune response, neuropsychological functioning, physical performance, preeclampsia, and reproductive outcomes. This thorough review found that information about the health benefits beyond bone health-benefits often reported in the media-were from studies that provided often mixed and inconclusive results and could not be considered reliable. However, a strong body of evidence from rigorous testing substantiates the importance of vitamin D and calcium in promoting bone growth and maintenance.
Dietary Reference Intakes
The DRIs are intended to serve as a guide for good nutrition and provide the basis for the development of nutrient guidelines in both the United States and Canada. The science indicates that on average 500 milligrams of calcium per day meets the requirements of children ages 1 through 3, and on average 800 milligrams daily is appropriate for those ages 4 through 8 (see table for the Recommended Dietary Allowance-a value that meets the needs of most people). Adolescents need higher levels to support bone growth: 1,300 milligrams per day meets the needs of practically all adolescents. Women ages 19 through 50 and men up to 71 require on average 800 milligrams daily. Women over 50 and both men and women 71 and older should take in 1,000 milligrams per day on average to ensure they are meeting their daily needs for strong, healthy bones.
Determining intake levels for vitamin D is somewhat more complicated. Vitamin D levels in the body may come from not only vitamin D in the diet but also from synthesis in the skin through sunlight exposure. The amount of sun exposure one receives varies greatly from person to person, and people are advised against sun exposure to reduce the risk of skin cancer. Therefore, the committee assumed minimal sun exposure when establishing the DRIs for vitamin D, and it determined that North Americans need on average 400 International Units (IUs) of vitamin D per day (see table for the Recommended Dietary Allowances- values sufficient to meet the needs of virtually all persons). People age 71 and older may require as much as 800 IUs per day because of potential changes in people’s bodies as they age.
Questions About Current Intake
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. In contrast, postmenopausal women taking supplements may be getting too much calcium, thereby increasing their risk for kidney stones.
Information from national surveys shows vitamin D presents a complicated picture. While the average total intake of vitamin D is below the median requirement, national surveys show that average blood levels of vitamin D are above the 20 nanograms per milliliter that the IOM committee found to be the level that is needed for good bone health for practically all individuals. These seemingly inconsistent data suggest that sun exposure currently contributes meaningful amounts of vitamin D to North Americans and indicates that a majority of the population is meeting its needs for vitamin D. Nonetheless, some subgroups-particularly those who are older and living in institutions or who have dark skin pigmentation-may be at increased risk for getting too little vitamin D.
Before a few years ago, tests for vitamin D were conducted infrequently. In recent years, these tests have become more widely used, and confusion has grown among the public about how much vitamin D is necessary. Further, the measurements, or cut-points, of sufficiency and deficiency used by laboratories to report results have not been set based on rigorous scientific studies, and no central authority has determined which cut-points to use. A single individual might be deemed deficient or sufficient, depending on the laboratory where the blood is tested. The number of people with vitamin D deficiency in North America may be overestimated because many laboratories appear to be using cut-points that are much higher than the committee suggests is appropriate.
Tolerable Upper Levels of Intake
The upper level intakes set by the committee for both calcium and vitamin D represent the safe boundary at the high end of the scale and should not be misunderstood as amounts people need or should strive to consume. While these values vary somewhat by age, as shown in the table, the committee concludes that 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.
As North Americans take more supplements and eat more of foods that have been fortified with vitamin D and calcium, it becomes more likely that people consume high amounts of these nutrients. 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. Strong evidence about possible risks for daily vitamin D at lower levels of intake is limited, but some preliminary studies offer tentative signals about adverse health effects.
Scientific evidence indicates that calcium and vitamin D play key roles in bone health. The current evidence, however, does not support other benefits for vitamin D or calcium intake. More targeted research should continue. However, the committee emphasizes that, with a few exceptions, all North Americans are receiving enough calcium and vitamin D. Higher levels have not been shown to confer greater benefits, and in fact, they have been linked to other health problems, challenging the concept that "more is better."