Food and Behaviour Research

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Vitamin D and asthma: a case to answer

Beasley R and Weatherall M (2017) Lancet 2017 Oct. 

Web URL: Read the full study on The Lancet here


The role of vitamin D in human health is an enigma. Associations have been reported between low serum concentrations of 25-hydroxyvitamin D (25[OH]D) and a wide range of disorders and diseases, including (but not limited to) cancer, cardiovascular disease, metabolic disorders, infectious diseases, autoimmune diseases, pregnancy-related outcomes, skeletal disorders, respiratory disease, multiple sclerosis, mental health disorders, and inflammation, as well as mortality.

If causal, these associations would suggest that vitamin D deficiency can cause a substantive burden of disease and mortality, particularly in populations in which vitamin D deficiency is prevalent, and that supplementation with vitamin D could have widespread therapeutic benefits. However, the highly promising results identified from observational studies have either not been tested or not replicated in most of the randomised controlled trials. The discrepancy between observational and intervention studies suggests that low 25(OH)D might be a marker of poor health, possibly related to the inflammatory processes involved in disease occurrence and clinical course, which would reduce 25(OH)D levels.

Certainly there is a case to answer and definitive well powered randomised placebo controlled trials need to be done as a priority because the magnitude of the reduction in risk of severe exacerbations with vitamin D reported in this meta-analysis is substantial. Considering that vitamin D deficiency is prevalent in many countries in which the burden of asthma is high and that vitamin D is a low cost intervention, its supplementation represents a potentially effective, low-cost medication with a favourable safety profile.

In addition to determining the efficacy of vitamin D supplementation in asthma, future randomised controlled trials must also be sufficiently powered and designed to identify whether characteristics such as 25(OH)D level, age, sex, BMI, ethnicity, or asthma severity can predict which patients might preferentially respond to treatment, as suggested might be the case in this meta-analysis.
 If true then the specific characteristic of the patient would represent a treatable trait and allow a precision medicine approach to be implemented.