Barchetta 2016.

Study characteristics
Methods	Randomised clinical trial with parallel‐group design (2 groups)
Participants	65 participants (35% women), mean age 59 years, with NAFLD Inclusion criteria: men or women aged 25 to 70 years; diagnosis of type 2 diabetes according to American Diabetes Association 2009 criteria; presence of fatty liver detected by upper US and confirmed by MRI in people with clinical suspicion of NAFLD (increased serum transaminase levels in absence of known hepatic chronic disease, ALT > AST, presence of multiple components of metabolic syndrome); negative tests for hepatitis B surface antigen and antibody to HCV Exclusion criteria: history of alcohol abuse (defined by mean daily consumption of alcohol > 30 g/day in men and > 20 g/day in women), cirrhosis, autoimmune hepatitis and other causes of liver disease (haemochromatosis, Wilson's disease), chronic enteropathies, advanced renal failure, cancer, hyper/hypoparathyroidism, known hypersensitivity to cholecalciferol or any other excipients, hypercalcaemia, hypercalciuria, nephrolithiasis, nephrocalcinosis; ongoing/recent (previous 6 months) supplementation with vitamin D, calcium, multivitamin products; treatment with agents affecting bone and calcium/vitamin D metabolism (anticonvulsants, glucocorticoids, antacids containing aluminium, cholestyramine); ultraviolet radiation exposure; pregnancy and lactation; or severe psychiatric illnesses
Interventions	Intervention: vitamin D3 2000 IU/day (n = 29) Control: placebo (n = 36) For 24 weeks
Outcomes	Primary outcomes: reduction of hepatic fat fraction measured by MRI, changes in serum transaminases, CK18‐M30, N‐terminal procollagen III propeptide levels, and Fatty Liver Index Secondary outcomes: metabolic (fasting glycaemia, glycated haemoglobin, lipids, homeostasis model assessment ‐ insulin resistance, homeostasis model assessment ‐ beta cell function, adipose tissue insulin resistance, body fat distribution) and cardiovascular (ankle‐brachial index, intima‐media thickness, flow‐mediated dilatation) parameters
Stated aim of study	To assess the efficacy and safety of 24‐week oral high‐dose vitamin D supplementation in people with type 2 diabetes and NAFLD
Notes	Registered at www.clinicaltrialsregister.eu (number 2011‐003010‐17). Funded by research grants from the Sapienza University Ateneo Scientific Research (authors MGC and IB) and the Italian Minister of University and Research (authors MGC and MGB). Study authors did not report any deaths. Authors were not contacted, as information on our outcomes of interest was found in the publication: “As per the safety profile, no major adverse events occurred during the study”.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Randomisation performed by statistician using computer‐generated and centrally administered procedure
Allocation concealment (selection bias)	Low risk	Participant allocations could not have been foreseen in advance of, or during, enrolment. Used central and independent randomisation unit‐controlled allocation
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Participants, investigators, clinical site staff, laboratory staff, and radiologists were all masked to treatment assignment throughout study. Treatment and placebo provided in identical vials by an experienced independent pharmacist.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Blinding of outcome assessment ensured, and it is unlikely that blinding could have been broken.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Insufficient information to assess whether missing data in combination with method used to handle missing data was likely to introduce bias on the results
Selective reporting (reporting bias)	Low risk	Study authors reported all predefined outcomes in full.
Other bias	Low risk	Trial appeared to be free of other factors that could put it at risk of bias.