Madam
Late in 2010 the US Institute of Medicine (IOM) recommended that adults should have dietary intakes of vitamin D of 15 μg/d (20 μg/d in older adults), based on evidence that these intakes improve bone health(1). In the UK, the only one of thirty-one European countries to have no daily intake recommendation for vitamin D for adults between 19 and 64 years old(Reference Doets, de Wit and Dhonukshe-Rutten2), where current recommended intakes for pregnant women are 10 μg/d but where intakes average less than 5 μg/d(Reference Hypponen and Boucher3), the implementation of these recommendations would improve vitamin D repletion at the population level. The IOM found no evidence of other health benefits from the specifically delineated types of evidence that it reviewed. However, there is now a large body of evidence for associations of hypovitaminosis D with non-bony health disorders such as multiple sclerosis, diabetes types 1 and 2, CVD, wound healing, peridontitis, and bacterial, viral and tuberculous infections, as well as for many cancers(Reference Holick4). There is also much mechanistic evidence demonstrating how activated vitamin D produces protective effects for such diseases(Reference Holick5). But there is still a shortage of data from randomized controlled trials (RCT) giving supplemental vitamin D in doses of 20 μg/d or more for risk reduction of these disorders, so that causality has not been proven for each of these conditions. Despite this, the weight of evidence has led the WHO's International Agency for Research into Cancer to accept that hypovitaminosis D is causal for colonic cancer(6). The IOM report recommendations are for minimal intakes but their report also states that vitamin D intakes of up to 100 μg/d can be regarded as safe for healthy adults. While this sounds inconsistent, this considered conclusion should facilitate approval of RCT comparing vitamin D supplementation at up to 100 μg/d with currently recommended intakes, for their effects on many health outcomes, in order to establish both optimal vitamin D status and the intakes necessary for it to be achieved.
