In 2010, the Institute of Medicine issued a report saying that vitamin D is vital for bone health, but other than that there isn’t evidence that low levels of vitamin D cause disease.1
A 2014 review published in the British Medical Journal concluded that highly convincing evidence of a clear role of vitamin D supplementation does not exist for any outcome.2
In 2014, the U.S. Preventive Services Task Force concluded there’s not enough evidence to recommend screening for vitamin D deficiency in asymptomatic adults.3
The current standard for assessment of vitamin D status, measurement of 25(OH)D only, needs further investigation because levels deemed deficient are found in both healthy and sick individuals. Since 25(OH)D is an inert precursor of the bio-active form of vitamin D, measuring the active form [1,25(OH)2D] may provide valuable information for both the researcher and clinician.
It is presumed that 25(OH)D accurately reflects the level of 1,25(OH)2D. That may be the case in the healthy but measurement of 1,25(OH)2D in chronically ill patients with normal renal function may reveal a significant elevation. Extra-renal cells can be stimulated by intracellular bacteria to over-produce this steroid hormone in an effort to activate the immune system. The result is a depletion of its precursor – 25(OH)D. Thus, vitamin D “deficiency” may be a marker of an occult, infectious disease process.4
References
1. Dietary Reference Intakes for Calcium and Vitamin D http://www.npr.org/sections/health-shots/2014/11/24/366326677/vitamin-d-tests-arent-needed-for-everyone-federal-panel-says?utm_medium=RSS&utm_campaign=health
2. Theodoratou E, Tzoulaki I, Zgaga L, Ioannidis JP, Vitamin D and multiple health outcomes: umbrella review of systematic reviews and meta-analyses of observational studies and randomised trials, BMJ 2014;348:g2035. http://www.bmj.com/content/348/bmj.g2035?tab=related&utm_content=buffer810ad&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer
3. Clinical Summary: Vitamin D Deficiency: Screening. U.S. Preventive Services Task Force. November 2014. http://www.uspreventiveservicestaskforce.org/Page/Document/ClinicalSummaryFinal/vitamin-d-deficiency-screening
4. Mangin M, Sinha R, Fincher K. Inflammation and vitamin D: the infection connection. Inflamm Res. Oct 2014;63(10):803-19. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4160567/