25-hydroxyvitamin D deficiency is associated with decreased light exposure as quantified with actigraphy but not with dietary sources in patients with chronic liver diseases

Background: Patients with chronic liver diseases (CLD) commonly exhibit vitamin D deficiency due to a combination of exogenous and endogenous factors (Hepatology 2012;56:1883). It remains unknown to which extent CLD contribute to vitamin D deficiency. The aim of this study was to assess for possible associations of exogenous factors (sunlight exposure and dietary intake) with serum vitamin D levels in CLD patients.

Methods: Serum 25-hydroxyvitamin D concentrations were measured with chemiluminescence immunoassay in patients with CLD. We quantified light exposure using the accelerometer-based physical activity monitor ActiGraph GT3X with integrated ambient light sensor. Light intensity was reported as lux (lm/m2). Dietary intake was simultaneously captured in food diaries and analysed using EBISpro software. Bioelectrical impedance analysis determined body composition.

Results: We included 30 patients with a median age of 55 years (27 – 81), 63% were women and median BMI was 26.9 kg/m2 (19.3 – 39.2). Serum vitamin D concentrations correlated significantly (rs = 0.56, P = 0.02) with light exposure. When classifying patients according to vitamin D status, those with normal levels (> 30 ng/ml) had significantly (P = 0.009) higher daily exposure to all thresholds of lx intensities, as compared to patients with vitamin D deficiency. A seasonal comparison confirmed significantly higher lx accrued in spring and summer (P 30 min exposure at > 1000 lx/day (P = 0.002).

Conclusions: In CLD patients, serum vitamin D levels positively correlate with light exposure but not with dietary vitamin D intake. The contribution of vitamin D from diet is minimal and below the recently revised recommendations for vitamin D intake. Our findings emphasise the need for combined lifestyle interventions to overcome vitamin D deficiency in patients with CLD.