P658 Is vitamin D deficiency related to fat malabsorption or inflammation in Inflammatory Bowel Disease? Preliminary results from the Fat-D study

Abstract

Abstract Background Vitamin D deficiency is highly prevalent in patients with inflammatory bowel disease (IBD). The question of whether vitamin D status is a contributory factor or a consequence of IBD, or maybe both, remains unanswered, and is confounded by the complexity of inflammation, IBD and vitamin D. Fat malabsorption has been proposed as a possible reason for deficiencies of vitamin D in IBD. The aim of this study was to further understanding of vitamin D deficiency in IBD by investigating possible causal relationships of fat malabsorption and inflammation on vitamin D levels in this complex context. Methods In a comparative, cross-sectional study in IBD patients, 25(OH)D was analysed by LCMS/MS. Serum β-carotene levels were used as a biomarker for fat malabsorption. Vitamin K1, another fat-soluble vitamin, was used to affirm a possible causative relation between β-carotene and vitamin D in case of fat malabsorption. β-carotene and vitamin K were measured in serum by HPLC. Inflammation was characterised by serum hsCRP<5mg/L. Results 51 IBD patients (30f;20CD/18UC;45.3±16.3y; 21 with inflammatory activity) were enrolled. In patients with vs. without inflammation, serum 25(OH)D levels were significantly lower (26.5±14.6ng/mL vs. 36.8±12.6ng/mL, p<0.05), while serum vitamin K1 (1.4±0.5µg/L vs. 1.2±0.4µg/L) and β-carotene (28.5±0.6.0µg/dL vs. 35.9±5.4µg/dL) levels were similar (p>0.05). 36/51 of the patients had low serum β-carotene levels, indicating steatorrhoea. Neither 25(OH)D (32.1.5±13.8ng/mL vs. 33.6±15.8ng/mL) nor vitamin K1 (1.3±0.5µg/L vs. 1.2±0.4µg/L) levels differed according to the presence vs. absence of steatorrhoea (p>0.05). Similarly, no correlation was found for 25(OH)D (r=0.024, p=0.875) or serum vitamin K1 (r=0.111, p=0.462) with β-carotene levels. On the other hand, 25(OH)D levels were significantly inversely correlated with hsCRP (r=-0.338, p=0.015), whereas vitamin K1(r=0.050, p=0.731) and β-carotene (r=-0.118, p=0.438) did not show a similar relation. Conclusion Vitamin D levels were confirmed to be related to inflammation in IBD. A lack of correlation with fat malabsorption, as indicated by β-carotene levels, or with steatorrhoea, was found for vitamin D and confirmed by measuring and comparing serum levels of an additional fat-soluble vitamin, K1. We conclude that low vitamin D levels in patients with IBD are related to inflammation rather than fat malabsorption.