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New Measurement Technique Suggests Lower Recommended Daily Vitamin D Intake

Using a new measurement technique, researchers have found that the recommended dietary allowance (RDA) for vitamin D intake could be lowered from 800 international
units (IU) to 400 IU per day. In the past, the Institute of Medicine, World Health Organization, and European Food Safety authority have suggested that a serum 25-hydroxyvitamin D (25OHD) level of 20ng/ml is adequate to prevent fractures. Previous research has reported that 800 IU of vitamin D daily would allow 97.5% of the population
to meet this requirement. However, these estimates were based on analysis using immunoassay.

Now, using liquid chromatography mass spectrometry, researchers reevaluated samples originally measured with immunoassay in order to test their original estimations.
In the original study, the researchers randomly assigned 163 postmenopausal Caucasian women with vitamin D insufficiency, aged 57 to 90 years, to 1 of 7 vitamin D doses: 400,800, 1600, 2400, 3200, 4000, 4800 IU/day or to placebo, for 1 year. After reevaluating the results with liquid chromatography mass spectrometry, the researchers reported that a daily dose of 400 IU would exceed a serum 25OHD level of 20ng/ml and that an intake of 800 IU per day would exceed a serum 25OHD level of 30ng/ml.
“In estimating the RDA for vitamin D intake the method used for measuring serum 25-OH-D is an important consideration. Based on the [immunoassay] system the estimated
RDA to exceed 20ng/ml was 800 IU daily whereas [liquid chromatography mass spectrometry] estimated that 400 IU daily would meet the RDA. This has important ramifications for public health recommendations,” the researchers concluded. 

Smith LM, Gallagher JC, Jones G, Kaufmann M. Estimation of the recommended daily allowance (RDA) for vitamin d intake using serum 25 hydroxyvitamin d Level of 20ng/Ml as the end point, may vary according to the analytical measurement technique used. Presented at: ENDO 2017; April 2, 2017; Orlando, Florida. https://plan.core-apps.com/tristar_endo17/abstract/ f7e437ee5c-2d999047a0315444cbbebb.