Vitamin D guidelines are currently in a state
of paralysis.
The problem: the numerous competing ways of
measuring levels of 25-hydroxyvitamin D, a
slightly modified form of vitamin D in the
body.
This lack of standardization has produced
three conflicting sets of guidelines for defining
vitamin D status across the globe, those from
the UK, the US, and the Endocrine Society.
The guidelines from the UK and US set similar
standards, defining vitamin D deficiency as
25-hydroxyvitamin D concentrations less than
10 to 12 nanograms per milliliter.
This is the standard typically adopted by
government-sponsored committees.
Non-governmental organizations, however, tend
to adopt the guideline set by the Endocrine
Society, which defines deficiency as 25-hydroxyvitamin
D concentrations less than 20 nanograms per
milliliter.
Despite a wealth of data on vitamin D and
how to measure it, a worldwide consensus on
determining vitamin D status remains elusive.
And that’s a problem, as rates of vitamin
D deficiency only continue to grow.
In a commentary recently published in the
journal Public Health Nutrition, the authors
describe the origins of this problem and propose
a set of recommendations for establishing
standard vitamin guidelines.
Their recommendations are based on the NIH’s
Vitamin D Standardization Program (VDSP) and
focus on standardizing measurements of 25-hydroxyvitamin D in all research and representative national surveys.
Standardization includes the selection and
use of assays that are fit for purpose, meaning
that they will perform appropriately and provide
standardized measurements in the patient populations
for which they will be used.
The authors also recommend that funding organizations
and journals join in the effort by incentivizing
work that adheres to assay standardization.
That includes publishing only meta-analyses
based on guidelines set by the Vitamin D Standardization
Program and fit-for-purpose assays.
To be sure, much work remains to be done.
But without assay standardization, the current
paralysis that plagues the vitamin D community
will persist.
