Health impacts of vitamin D: are we getting enough?

Increasingly, scientists are debating whether photochemical synthesis of vitamin D in Western countries is adequate, and whether dietary intakes can plug the gap between endogenous vitamin D production and requirements, particularly in young and older populations. The debate is driven by the plethora of evidence suggesting that, in addition to its important role in maintaining bone health, vitamin D may be involved in ameliorating cell ageing and preventing cardiovascular disease, diabetes, immune dysfunction and some cancers. Observational evidence from different populations suggests a significant degree of vitamin D insufficiency, often defined as plasma 25-hydroxyvitamin D [25(OH) D] <25 nmol/l. Some experts have argued that daily intakes up to 40 mu g/day may be needed to ensure a desirable vitamin D status, even after accounting for sun exposure. However, there is presently no consensus on the most appropriate vitamin D status for maintaining bone health and preventing chronic disease. In addition, the UK has not set a vitamin D recommendation for most adults under 65 years. Given the plethora of information about vitamin D and bone health, this article reviews evidence for a link between vitamin D and other aspects of health. In conclusion, three actions are suggested: (1) agreement on optimal plasma 25(OH) D levels for health; (2) a debate on whether UK dietary recommendations need revision; and (3) better promotion of dietary vitamin D via food sources and, for certain groups, supplements.