by Craig Weatherby
The semi-official advisory body that sets the U.S. recommended daily allowances (RDAs) for nutrients just issued a long-awaited report on vitamin D and calcium.
After its 14-member panel looked at the evidence, the Institute of Medicine (IOM) raised the RDAs for vitamin D substantially… though not as much as many researchers wanted.
IOM panel cites lack of clinical evidence for disease prevention
Laboratory, animal, and epidemiological studies continue to produce evidence that vitamin D affects an unusually broad array of body functions and systems in very powerful ways.
The sheer volume of this positive non-clinical evidence has persuaded many researchers and doctors that high blood levels of this unique, hormone-like nutrient can help deter major diseases.
But scientists charged with making public health recommendations must hew to a high standard of proof.
If they jump the gun and their advice later proves faulty, they'll further confuse people about nutrients' disease-prevention powers and undermine faith in official, ostensibly evidence-based recommendations.
While we may believe that the evidence justifies even higher RDAs, we understand the professional and institutional constraints that led the IOM committee to make its more conservative recommendations on daily intakes… which still represent a substantial improvement.
This is good news, given the growing evidence that higher-than-average blood levels of vitamin D help prevent major diseases.
But this positive step has been overshadowed by the panel's refusal to declare that higher blood levels of vitamin D help prevent cancer, heart disease, infections, or auto-immune disorders.
We are not really surprised by this reticence, because the IOM committee lacked the kind and quantity of clinical evidence needed to decide that high vitamin D blood levels definitely reduce the risk of disease.
However, using a common definition of adequate blood levels, analyses of data from the National Health and Nutritional Examination Surveys indicate that large segments of the population—especially darker-skinned people—have inadequate vitamin D blood levels.
And as the IOM panel acknowledged, a growing body of evidence associates low vitamin D levels with increased risks for certain cancers, cardiovascular disease, osteoporosis, diabetes, and auto-immune diseases… without absolutely proving a cause-and-effect relationship between low vitamin D levels and the risks of these ills.
To read our coverage of some of these studies, visit our news archive and click on the various subtopics under the Vitamin D topic in the right-hand column.
Institute of Medicine triples the adult RDAs for vitamin D
The IOM's expert committee established higher RDAs and safe intake limits for vitamin D (see the chart below for more detail):
The RDA for infants from birth to one year doubled, going from 200 IU to 400 IU.
The RDA for people aged one to 70 years tripled, going from 200 IU to 600 IU.
The RDA for people aged 71 or more goes from 600 IU to 800 IU.
The Tolerable Upper Intake Level—the safe intake limit—for adults doubled, going from 2,000 IU to 4,000 IU per day.
When it came to setting adequate blood levels of vitamin D, the IOM report retained the prior recommended minimum, which is 20 nanograms per milliliter (ng/mL).
However, many doctors and researchers recommend 30 ng/mL or more, based on evidence that this higher level is associated with lower risk of major diseases… but the committee found no conclusive evidence for those hypotheses, and no evidence of bone-health advantages from raising blood levels above 20 ng/mL.
For example, leading vitamin D researcher Michael F. Holick, Ph.D., M.D., of Boston University Medical Center says the evidence supports keeping vitamin D levels above 30 ng/mL, and says that levels up to 100 ng/mL are “perfectly safe” … unless you have an uncommon inflammatory disease called sarcoidosis, which often raises vitamin D levels in the body.
You can see his full initial response below... see “Leading vitamin D expert calls the IOM action inadequate.”
The IOM made these points (verbatim) in its press release (IOM 2010):
The report's recommendations take into account nearly 1,000 published studies as well as testimony from scientists and stakeholders.
A large amount of evidence, which formed the basis of the new intake values, confirms the roles of calcium and vitamin D in promoting skeletal growth and maintenance and the amounts needed to avoid poor bone health.
The committee that wrote the report also reviewed hundreds of studies and reports on other possible health effects of vitamin D, such as protection against cancer, heart disease, autoimmune diseases, and diabetes. While these studies point to possibilities that warrant further investigation, they have yielded conflicting and mixed results and do not offer the evidence needed to confirm that vitamin D has these effects.
Rigorous trials that yield consistent results are vital for reaching conclusions, as past experiences have shown. Vitamin E, for example, was believed to protect against heart disease before further studies disproved it.
Leading vitamin D expert calls the IOM action inadequate
We went to the very top of the field to get a response to the IOM's report, contacting Michael F. Holick, Ph.D., M.D., who is Professor of Medicine, Physiology and Biophysics at Boston University Medical Center.
Among other roles, he's also Director of BU Medical Center's Bone Health Care Clinic, and Director of its Heliotherapy, Light, and Skin Research Center.
Dr. Holick has made critical contributions to the field of vitamin D research, being the first to identify the major circulating form of vitamin D in human blood (25-hydroxyvitamin D3) and the active form of vitamin D (1,25-dihydroxyvitamin D3).
He also discovered how vitamin D is synthesized in the skin, and demonstrated the effects of aging, obesity, latitude, seasonal change, sunscreen use, skin pigmentation, and clothing on this vital process.
His recent book, The Vitamin D Solution, is the best available resource for doctors and laypersons alike … read our April 2010 review, “Vitamin D Expert's Book Says it All” for links to buy the book and to a great video of Dr. Holick speaking on the subject.
We asked him for comments, and he sent us his initial response, which is posted on his website. Note: To make reading easier, we substituted “vitamin D” where Dr. Holick wrote “25-hydroxyvitamin D”, which is the active form of the vitamin:
“My take is that the IOM at least recognized that the last recommendations were woefully inadequate and have recommended for both children and adults to increase their vitamin D intake by 200%.
“This is a step in the right direction but they still need to go further. There is no downside to increasing vitamin D intake. The recent study in Japanese children demonstrating in a randomized placebo-controlled trial that taking 1200 IU of vitamin D a day from December through March during the past year reduced their risk of developing influenza A infection by almost 50% is just one reason why physicians should continue to recommend that children receive at least 1000 IU of vitamin D a day and adults receive 2000-3000 IU of vitamin D a day.
“We published a paper In Archives of Internal Medicine in December last year reporting that among my patients who have been taking the equivalent of 3000 IU of vitamin D a day for up to six years, this dose was safe and effective in maintaining their blood levels of vitamin D between 40-60 ng/mL.
“In 1998 we reported in the Lancet the redefinition of vitamin D deficiency which at that time was a vitamin D level of less than 10 ng/mL. We demonstrated that calcium and vitamin D supplementation in adults who had a blood level of vitamin D of less than 20 ng/mL markedly reduced their PTH [parathyroid hormone, which enables calcium absorption] levels until the vitamin D level reached 20 ng/mL.
“Therefore the [IOM's recommended blood level minimum] of 20 ng/mL in my opinion is the barely adequate level of vitamin D, and to ensure vitamin D's maximum effect on bone health and overall health and well-being I encourage physicians to [advise their patients to] maintain blood levels of vitamin D above 30 ng/mL and up to 100 ng/mL, [which] is perfectly safe unless you have sarcoidosis.”
– Michael F. Holick, Ph.D., M.D., December 2, 2010
Calcium RDAs unchanged in IOM report
The Committee also looked at the evidence on calcium, and left the RDAs at their prior levels:
700 mg from age 1 through 3.
1,000 mg for children from age 4 through 8.
1,300 mg for children and adolescents from age 9 through 18.
1,000 mg from age 19 through 50 for women and for men until the age of 71.
1,200 mg for women aged 51 or older and for men and women aged 71 and older.
According to IOM committee chair A. Catharine Ross, Ph.D., of Pennsylvania State University, supplementation still is appropriate for some groups, including calcium for girls aged 9-18 years and older women… despite the committee's findings that the majority of people in North America receive adequate levels from foods.
Institute of Medicine (IOM). IOM Report Sets New Dietary Intake Levels for Calcium and Vitamin D To Maintain Health and Avoid Risks Associated With Excess. Nov. 30, 2010. Accessed at http://www8.nationalacademies.org/onpinews/newsitem.aspx?RecordID=13050
Personal correspondence from Michael F. Holick, Ph.D., M.D., to Randy Hartnell, December 2, 2010.