Role of Vitamin D in Preventing and Treating Selected Extraskeletal Diseases—An Umbrella Review

Abstract

Evidence is accumulating that vitamin D may have beneficial effects on respiratory tract, autoimmune, neuro-degenerative, and mental diseases. The present umbrella review of systematic reviews (SRs) of cohort studies and randomised controlled trials (RCTs), plus single Mendelian randomisation studies aims to update current knowledge on the potential role of vitamin D in preventing and treating these extraskeletal diseases. Altogether, 73 SRs were identified. Observational data on primary prevention suggest an inverse association between vitamin D status and the risk of acute respiratory tract infections (ARI), dementia and cognitive decline, and depression, whereas studies regarding asthma, multiple sclerosis (MS), and type 1 diabetes mellitus (T1DM) are scarce. SRs of RCTs support observational data only for the risk of ARI. No respective RCTs are available for the prevention of chronic obstructive pulmonary disease (COPD), MS, and T1DM. SRs of RCTs indicate beneficial therapeutic effects in vitamin D-deficient patients with asthma and COPD, while effects on major depression and T1DM need to be further elucidated. Mendelian randomisation studies do not consistently support the results of SRs. Since several limitations of the included SRs and existing RCTs do not permit definitive conclusions regarding vitamin D and the selected diseases, further high-quality RCTs are warranted.

The effects of vitamin D on acute viral respiratory infections: A rapid review

“…See Table 1 for a summary of all included studies in the final, detailed review. Of the 20 studies, 13 were systematic reviews and/or of meta-analysis [ [16] , [17] , [18] , [19] , [20] , [21] , [22] , [23] , [24] , [25] , [26] , [27] ], 3 were systematic reviews of randomised controlled trials (RCTs) [ [28] , [29] , [30] ], 2 were systematic reviews of various studies [ 14 , 31 ] and 1 was a detailed narrative review of RCTs (and therefore was included), despite low formal quality of design [ 15 ]. The 2 systematic reviews with various studies included RCTs, cohort studies, case-control series, retrospective case studies and cross-sectional studies [ 14 , 31 ].…”

“…The 2 systematic reviews with various studies included RCTs, cohort studies, case-control series, retrospective case studies and cross-sectional studies [ 14 , 31 ]. The majority of reviews searched 3 or more databases with Pubmed, Embase, Cochrane, Cinahl and Medline being the main ones [ 15 , [17] , [18] , [19] , [20] , [21] , [22] , [23] , [25] , [26] , [27] , [28] , [29] , [30] , [31] , [32] ]. Two studies only used one database, Pubmed [ 14 , 33 ] and 1 didn’t specify the databases searched [ 16 ].…”

“…The study population and size, type of respiratory condition, form and dose, and administration route or screening of vitamin D varied across the studies reviewed. Fourteen studies included all populations including children, adults and elderly [ [14] , [15] , [16] , [17] , [18] , 20 , 22 , 23 , [26] , [27] , [28] , [29] , [30] , 32 ] and 5 reviews were conducted on children only [ 19 , 21 , 24 , 31 ], 1 was for pregnant women and children [ 25 ] and 1 for children and young men [ 33 ]. The number of studies included for the reviews on children included 26 in total, encompassing 12 RCTs, 3 cohort, 2 cross-sectional and 9 case-control studies [ 19 , 21 , 24 , 31 ].…”

“…The fourteen studies that included all population groups comprised a total sample of 314,979 participants; of those reviews reporting group allocation, there were 41,738 participants in intervention arms and 39,655 participants in placebo arms. [ [14] , [15] , [16] , [17] , [18] , 20 , 22 , 23 , [26] , [27] , [28] , [29] , [30] , 32 ].…”

“…Sixteen reviews addressed oral administration of vitamin D [ [15] , [16] , [17] , [19] , [20] , [21] , [22] , [23] , [24] , [25] , [26] , [27] , 30 , 31 , 33 ], 2 reviews addressed intravenous and oral administration of vitamin D [ 29 , 32 ] and 3 reviews did not state the route of administration (and focused solely on serum concentrations of vitamin D) [ 14 , 18 , 28 ].…”