Vitamin D – what is normal according to latest research and how should we deal with it?
Editor – This interesting article summarised the public health concern presented by vitamin D deficiency. The observational data that links vitamin D deficiency to many chronic diseases demonstrates a potential impact extending far beyond traditionally recognised endocrine effects on bone health. The benefits of vitamin D supplementation, in the absence of randomised controlled trial data, are currently yet to be fully defined.
The author advocates ‘a targeted, rather than population-based screening approach to vitamin D testing’, but adds that ‘empirical supplementation of at risk groups should be considered’.1 Any strategy that includes blanket vitamin D supplementation should be approached with caution: certain individuals in the population will have a genetic predisposition to vitamin D toxicity, unmasked only through higher vitamin D intake.
In the 1950s, routine supplementation of formula milk products with vitamin D3, in an effort to prevent rickets, led to a sudden increase in infants presenting with idiopathic infantile hypercalcaemia, in some cases proving fatal.2 Almost 60° years later, the discovery of loss-of-function mutations in CYP24A1, which encodes vitamin D 24-hydroxylase – an enzyme with a key role in vitamin D catabolism – finally linked these events.3 Furthermore, an adult cohort who present with calcium-containing renal stones and nephrocalcinosis are recognised to carry CYP24A1 mutations.4
At present, the population frequency of CYP24A1 variants has not been established.5 The rarity of these presentations often leads to delayed diagnosis, a feature that will hopefully change with increased awareness and easier access to diagnostic testing.
As research into vitamin D supplementation expands, we must be careful to tailor our treatment towards each individual, and remember that Vitamin D supplements are not the answer for everyone.
Conflicts of interests
The author has no conflicts of interests.
- © 2016 Royal College of Physicians
References
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- Gittoes NJL.
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- British Paediatric Association
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- Sayers J
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