Vitamin D and Multiple Health Outcomes: An Umbrella Review of Observational Studies, Randomized Controlled Trials, and Mendelian Randomization Studies.
Study Goal
The researchers aimed to evaluate the effects of low vitamin D concentrations and vitamin D supplementation on multiple health outcomes by summarizing evidence from meta-analyses of observational studies, RCTs, and MR studies.
Results Summary
Lower vitamin D concentrations were associated with higher risks for all-cause mortality, Alzheimer's disease, hypertension, schizophrenia, and type 2 diabetes. Vitamin D supplementation reduced all-cause mortality but did not significantly affect the risk for Alzheimer's disease, hypertension, schizophrenia, or type 2 diabetes.
Population
General population (no specific subgroup mentioned)
Effective Dosage
Not specified
Duration
Not specified
Interactions
None mentioned
| Intervention | Direction | Endpoint | Population | Dosage | Impact | Claim # |
|---|---|---|---|---|---|---|
low vitamin D concentrations | increase | all-cause mortality | - | - | were associated with a higher risk for | #1 |
low vitamin D concentrations | increase | Alzheimer's disease | - | - | were associated with a higher risk for | #2 |
low vitamin D concentrations | increase | hypertension | - | - | were associated with a higher risk for | #3 |
low vitamin D concentrations | increase | schizophrenia | - | - | were associated with a higher risk for | #4 |
low vitamin D concentrations | increase | type 2 diabetes | - | - | were associated with a higher risk for | #5 |
vitamin D supplementation | decrease | all-cause mortality | - | - | was associated with a decreased risk for | #6 |
vitamin D supplementation | no change | Alzheimer's disease | - | - | not associated with the risk for | #7 |
vitamin D supplementation | no change | hypertension | - | - | not associated with the risk for | #8 |
vitamin D supplementation | no change | schizophrenia | - | - | not associated with the risk for | #9 |
vitamin D supplementation | no change | type 2 diabetes | - | - | not associated with the risk for | #10 |
Observational studies, randomized controlled trials (RCTs), and Mendelian randomization (MR) studies have yielded inconsistent results on the associations of vitamin D concentrations with multiple health outcomes. In the present umbrella review we aimed to evaluate the effects of low vitamin D concentrations and vitamin D supplementation on multiple health outcomes. We summarized current evidence obtained from meta-analyses of observational studies that examined associations between vitamin D concentrations and multiple health outcomes, meta-analyses of RCTs that investigated the effect of vitamin D supplementation on multiple health outcomes, and MR studies that explored the causal associations of vitamin D concentrations with various diseases (international prospective register of systematic reviews PROSPERO registration number CRD42018091434). A total of 296 meta-analyses of observational studies comprising 111 unique outcomes, 139 meta-analyses of RCTs comprising 46 unique outcomes, and 73 MR studies comprising 43 unique outcomes were included in the present umbrella review. Twenty-eight disease outcomes were identified by both meta-analyses of observational studies and MR studies. Seventeen of these reported disease outcomes had consistent results, demonstrating that lower concentrations of vitamin D were associated with a higher risk for all-cause mortality, Alzheimer's disease, hypertension, schizophrenia, and type 2 diabetes. The combinations of consistent evidence obtained by meta-analyses of observational studies and MR studies together with meta-analyses of RCTs showed that vitamin D supplementation was associated with a decreased risk for all-cause mortality but not associated with the risk for Alzheimer's disease, hypertension, schizophrenia, or type 2 diabetes. The results indicated that vitamin D supplementation is a promising strategy with long-term preventive effects on multiple chronic diseases and thus has the potential to decrease all-cause mortality. However, the current vitamin D supplementation strategy might not be an efficient intervention approach for these diseases, suggesting that new strategies are highly needed to improve the intervention outcomes.