Vitamin D status as a synthetic biomarker of health status

A considerable number of ecological, cross-sectional and of observational studies have documented the association between low vitamin D status (assessed by the measurement of serum 25-hydroxyvitamin D concentration [25(OH)D]) and a greater risk of being diagnosed with a myriad of diseases, including minor ailments and rare conditions [1]. Many have concluded from these non-interventional studies that low vitamin D status could be a cause of ill health, and that maintaining a high 25(OH)D could represent an easy way to prevent diseases and increase life expectancy. But the numerous randomised trials done to date on vitamin D supplementation did not confirm the health benefits of increased 25(OH)D, even when high doses of supplementation (i.e. ≥50 µg per day) were used in subjects with low vitamin D status before randomisation [2]. Large-size randomised trials on vitamin D supplementation are on-going [3, 4]. While awaiting for results of these trials, perhaps the cautious view is to consider that low 25(OH)D is a consequence and not a cause, of debilitated health.