Vitamin D supplementation
Raises 25-OH vitamin D reliably. VITAL and D-Health were null on the clinical endpoints.
Dose in the studies
In the underlying studies: The doses used in the large trials, not megadoses.. That is the reported study figure, not a recommendation to take it.
A supplement is not a lifestyle recommendation. Speak with your doctor.
The level responds, the outcomes do not.
Effects in detail
Each row is a directed edge from our database, with range, latency, evidence grade and the condition under which it applies at all.
| Marker | Effect | Latency | Mode of action | Outcome | Evidence | Condition | Sources |
|---|---|---|---|---|---|---|---|
| Systolic blood pressure | helps. Lowers Direction known, size not established Eleven randomised trials in people with both hypertension and hypovitaminosis D found a significant reduction in systolic blood pressure and no effect on diastolic pressure. No effect size is entered because the abstract reports significance without a pooled magnitude (gaps_batch2.md G-VD3). | 8–8 weeks | chronic | no | Evidence grade B | applies regardless of the starting value | |
| HbA1c | helps. Lowers -0.30 percentage points of HbA1c confidence interval of the estimate, not the range one person can expect Thirty-nine randomised trials in 2982 people with type 2 diabetes give an HbA1c reduction of 0.30 percentage points (95 % CI -0.43 to -0.18), with fasting glucose -0.49 mmol/L and HOMA-IR -0.39. outcome_proven is set to no, not unclear: the surrogate moves and the two definitive outcome trials are null. | not specified | chronic | no | Evidence grade A | applies regardless of the starting value | |
| HOMA-IR | helps. Lowers -0.39 HOMA-IR units confidence interval of the estimate, not the range one person can expect Across 39 randomised trials in 2982 people with type 2 diabetes, vitamin D lowered HOMA-IR by 0.39 (95 % CI -0.64 to -0.14), fasting glucose by 0.49 mmol/L and HbA1c by 0.30 percentage points. outcome_proven 'no' for the same reason as the other vitamin D rows. | not specified | chronic | no | Evidence grade B | applies regardless of the starting value |
What this measure costs
Counteracting effects of the same measure.
No counteracting effect is on file for this measure. That does not mean there is none, only that we found no defensible edge.
Moves without implying progress
Informational or no established effect: the marker moves or was checked, and that is not progress.
| Marker | Effect | Latency | Mode of action | Outcome | Evidence | Condition | Sources |
|---|---|---|---|---|---|---|---|
| Diastolic blood pressure | checked, nothing happens. No established effect Eleven randomised trials in people with both hypertension and hypovitaminosis D found a significant reduction in systolic blood pressure and no effect on diastolic pressure. No effect size is entered because the abstract reports significance without a pooled magnitude (gaps_batch2.md G-VD3). | 8–8 weeks | chronic | no | Evidence grade B | applies regardless of the starting value | |
| high-sensitivity CRP | moves, and does not count. Lowers -1.08 mg/L confidence interval of the estimate, not the range one person can expect Ten randomised trials in 924 participants gave a hs-CRP reduction of 1.08 mg/L (95 % CI -2.13 to -0.03). outcome_proven is 'no' rather than 'unclear': the large outcome trials have been done and were null. | not specified | chronic | no | Evidence grade B | applies regardless of the starting value | |
| 25-OH vitamin D | moves, and does not count. Raises Direction known, size not established the bounds are the rise at 600 IU/day for 12 weeks in women starting low (+17.0) and in women starting higher (+9.7); which applies depends on the person's own baseline 600 IU/day for 12 weeks raised 25(OH)D from 38.1 to 55.1 nmol/L in women with a low baseline and from 75.1 to 84.8 nmol/L in women with a higher one, with no change on placebo. Grade A for the effect on the marker and outcome_proven 'no' for the effect on disease. | 12–12 weeks | chronic | no | Evidence grade A | applies regardless of the starting value |
Sources
Full details of every study the rows above rely on.
Effect of vitamin D supplementation on the level of circulating high-sensitivity C-reactive protein: a meta-analysis of randomized controlled trials
Chen et al. · Nutrients · 2014 · Meta-analysis
Efficacy of vitamin D supplementation on glycaemic control in type 2 diabetes: an updated systematic review and meta-analysis of randomized controlled trials
Chen et al. · Diabetes, Obesity and Metabolism · 2024 · Meta-analysis
Vitamin D Supplements and Prevention of Cancer and Cardiovascular Disease (VITAL)
Manson et al. · New England Journal of Medicine · 2019 · Randomised trial
Vitamin D Supplementation and Sunlight Exposure on Serum Vitamin D Concentrations in 2 Parallel, Double-Blind, Randomized, Placebo-Controlled Trials
Mendes et al. · The Journal of Nutrition · 2021 · Randomised trial
A systematic review and meta-analysis of the response of serum 25-hydroxyvitamin D concentration to vitamin D supplementation from RCTs from around the globe
Mo et al. · European Journal of Clinical Nutrition · 2019 · Meta-analysis
The D-Health Trial: a randomised controlled trial of the effect of vitamin D on mortality
Neale et al. · Lancet Diabetes and Endocrinology · 2022 · Randomised trial
Effect of vitamin D supplementation on blood pressure in hypertensive individuals with hypovitaminosis D: a systematic review and meta-analysis
Serra et al. · Journal of Hypertension · 2024 · Meta-analysis