Abstract
BACKGROUND: Due to the high prevalence of vitamin-D deficiency worldwide and its health consequences, intervention studies at the community level are warranted. The present study has been conducted to evaluate the effectiveness of vitamin-D-fortified bread on serum vitamin-D levels, inflammatory and metabolic biomarkers, and gut microbiota composition in vitamin-D-deficient individuals. METHODS/DESIGN: A double-blind, randomized controlled clinical trial is conducted on apparently healthy individuals with vitamin-D deficiency. The random allocation is done to divide participants into intervention groups including daily intake of vitamin-D-3-fortified bread (FB) with 500 IU/100 g bread (n = 30), FB with 1000 IU/100 g bread (n = 30), and 100 g plain bread (PD) (n = 30). At baseline and after 3 months of the intervention period, blood, stool, and urine samples are taken. Anthropometric measures, body composition, blood pressure, and dietary assessment are made. The gut microbiome composition is measured by the 16S rRNA approach. Data is analyzed by SPSS software version 21. DISCUSSION: This study may partly explain for the first time the conflicting results from recent critical and systematic reviews regarding the role of vitamin D in microbiota composition. TRIAL REGISTRATION: Iranian Registry of Clinical Trials (IRCT), ID: IRCT20170812035642N3. Registered on 11 March 2018; http://www.irct.ir/user/trial/28134/view.