Vitamin D: What is the right level?
This first article highlights a point about RDA/DRI's that I have discussed here before. They are not individual requirements but populations goals and most of us can do fine if we just average ~70%)
Vitamin D Deficiency — Is There Really a Pandemic?
NEJM 375;19 nejm.org November 10, 2016
https://www.nejm.org/doi/10.1056/NEJMp1608005"A common misconception is that the RDA functions as a “cut point” and that nearly the entire population must have a serum 25(OH)D level above 20 ng per milliliter to achieve good bone health. The reality is that the majority (about 97.5%) if the population has a requirement of 20 ng per milliliter or less. Moreover, by definition of an average requirement, approximately half the population has a requirement of 16 ng per milliliter (the EAR) or less. . These concepts are depicted in the population reference-value distribution shown in Panel A, which highlights the relationship between the EAR and the RDA.
In creating its framework for reference values, the IOM anticipated the inherent variability in nutrient requirements and there- fore established — and verified by statistical modeling4 — the goal of achieving population levels above the EAR, not the RDA. However, the literature is replete with misapplications of the RDA that treat it as a cut point. Many studies establish “inadequacy” using the RDA, though it is actually at the upper end of the spectrum of human need. Clearly, this approach misclassifies as “deficient” most people whose nutrient requirements are being met — thereby creating the appearance of a pandemic of deficiency.
Applying the correct method to data from the National Health and Nutrition Examination Survey (NHANES) for 2007 through 2010 reveals that 13% of Americans 1 to 70 years of age are “at risk” for vitamin D inadequacy. Less than 6% are deficient in vitamin D [serum 25(OH)D levels <12.5 ng per milliliter4]. The utility of measurement of parathyroid hormone (PTH) concentrations for identifying the optimal level of vitamin D remains controversial; the relationship between serum 25(OH)D and PTH is inconsistent, and no clear threshold defining “sufficiency” has been established.4 Vitamin D is a nutrient of concern, but these levels of deficiency do not constitute a pandemic.
Furthermore, using the RDA- associated serum concentrations of vitamin D to judge whether population groups have inadequate levels or to set intake goals for populations inflates the estimated prevalence of inadequacy and overestimates the needed in- take. Indeed, ensuring that 97.5% of the population attains or exceeds vitamin D levels of 20 ng per milliliter would require shifting the entire population to a higher intake (see graph in Panel B). This misapplication of RDA-asso-ciated concentrations could cause harm to people whose intake is pushed above the Tolerable Upper IntakeLevel(UL,the level at which there may be adverse effects), which the IOM has established as 4000 IU daily with a resulting serum 25(OH)D concentration of approximately 50 ng per milliliter (125 nmol per liter). A modeling study by Taylor et al. suggested that shifting the distribution of serum 25(OH)D concentrations in adults 19 to 70 years of age upward so that the RDA-associated concentration of 20 ng per milliliter was achieved in nearly everyone (all but 2.5% of the population) would mean that levels in some people would exceed the UL"And this one on measurement technique..
New measurement technique lowers estimated vitamin D recommended daily allowance
The Endocrine Society
April 02, 2017
https://www.endocrine.org/news-room/cur ... -allowanceORLANDO - After re-measurement of vitamin D by improved technology, the Recommended Dietary Allowance (RDA) for vitamin D intake drops from 800 to 400 International Units (IU) per day, new research reports. The results of the study will be presented Sunday, April 2, at ENDO 2017, the annual scientific meeting of the Endocrine Society, in Orlando, Fla.
"The RDA is easily achievable with a supplement of 400 IU in winter, when vitamin D levels are lowest in North America," said principal investigator J. Christopher Gallagher, M.D., professor and director of the Bone Metabolism Unit in the Division of Endocrinology of Creighton University School of Medicine in Omaha, Neb.
"This has important ramifications for public health recommendations. The amount of vitamin D needed, 400 IU daily, is less than the figure recommended by Institute of Medicine," said Gallagher, the study's principal investigator.
"In estimating the RDA for vitamin D intake, the laboratory method used for measuring serum 25-hydroxyvitamin D ̶ 25(OH)D ̶ can affect the results," he said. "The estimated RDA based on the older immunoassay (DiaSorin S.p.A., Salugia, Italy) system was 800 IU daily, whereas the newer liquid chromatography tandem-mass spectrometry (LC-MS/MS) technique estimated that 400 IU daily would meet the RDA."
In their earlier double-blind dose-response clinical trial in the winter and spring of 2007 to 2008, Gallagher and his colleagues enrolled 163 healthy postmenopausal Caucasian women 57 through 90 years of age with vitamin D insufficiency and followed them for 1 year. The women were at least 7 years postmenopausal and they had vitamin D insufficiency based on the World Health Organization cutoff (serum 25(OH)D 20 ng/ml or lower).
The participants were randomized to one of seven vitamin D3 doses: 400, 800, 1600, 2400, 3200, 4000, 4800 IU/day or placebo, for 1 year, and all the women were given calcium supplements to maintain a total calcium intake. After analyzing the samples and estimating the RDA using the older immunoassay, the authors reported that 800 IU daily would meet the vitamin D intake requirement for 97.5 percent of the population.
But now that liquid chromatography mass spectrometry (LC-MS/MS) has become the gold standard for measuring 25(OH)D, the researchers have reanalyzed the original samples using this new technology. Able to determine a more precise dose-response curve, they have calculated the RDA for vitamin D to be 400 IU daily.
"Remember, this RDA is for bone health only," Gallagher cautioned. "It may be different for other diseases. Although trials looking into cancer, diabetes, and other diseases are ongoing, we do not have information about this yet."