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Vd9.0
Vitamin D3 Research
Probably helpsHigh safety
72 peer-reviewed studies
What the evidence says
Probably helps
Vitamin D3 helped in about half (15/26) of the studies that measured an effect — promising, but not unanimous.
Most evidence is from high-quality meta-analyses and randomised trials published 2005–2026 with a typical study size of 871 participants.
Based on 72 studies · 28 meta-analyses · 14 RCTs · 290,341 total participants
Confidence
High
What the studies found
15helped9unclear2didn't help· 46 more without graded effect data
By outcome
Bone healthSupports bone mineral density and skeletal strength · 8-12 weeks
56 studies in the last 5 years · Latest meta-analysis: 2026
200520152026
1Type 2 diabetes incidenceMeta-AnalysisCited 9×n=5,205 · very large study2025
This meta-analysis examined the effects of Omega-3.
Tobias DK et al. · Nature communications (2025)
No clear effect
← WorseNo effectBetter →
Mean body mass index (BMI) was 27.5 kg/m2 (SD = 5.3), with 51% female and 17% Black race/ethnicity.
T2D incidence (cases/1000py) at median follow-up of 5.3 y was 3.98 for vitamin D and 4.37 for placebo (hazard ratio [HR] = 0.91; 95% confidence interval [CI] = 0.76, 1.09).
In conclusion, Vitamin D supplementation did not reduce T2D in older US adults, but a modest reduction was observed when meta-analyzed with prior trials.
2Hip fracture incidenceMeta-AnalysisCited 21×n=5,676 · very large study2023
Daily oral supplementation 800 IU of vitamin D3 plus 1200 mg of calcium reduces hip fracture and non-vertebral fracture in older people.
Manoj P et al. · International journal of older people nursing (2023)
Large benefit
← WorseNo effectBetter →
Likely real
The meta-analysis of seven RCTs on vitamin D3 plus calcium supplementation and hip fracture (n = 12,620) identified odds ratio (OR) of 0.75; 95% Confidence interval (CI): 0.64, 0.87; p = .0003.
A meta-analysis of the seven RCTs to identify the incidence of non-vertebral fracture gave the OR of 0.80; 95% CI: 0.72, 0.89; p < .0001.
A meta-analysis of three RCTs on femoral neck bone mineral density (BMD) (n = 483) gave a mean difference of 1.21; 95% CI: -0.79, 3.20; p = .24.
4Pain intensity in dysmenorrheaMeta-AnalysisCited 1×n=687 · large study2024
In conclusion, although substantial heterogeneity persists, vitamin D supplementation decreased pain intensity in patients with dysmenorrhea, especially in those with primary dysmenorrhoea.
Lin KC et al. · Nutrients (2024)
TSA revealed that the current RCTs provide sufficient information.
In subgroup analyses, vitamin D supplement reduced primary dysmenorrhoea pain but not secondary dysmenorrhoea pain.
In conclusion, although substantial heterogeneity persists, vitamin D supplementation decreased pain intensity in patients with dysmenorrhea, especially in those with primary dysmenorrhoea.
5Serum vitamin D repletionMeta-AnalysisCited 2×n=542 · large study2024
Limited direct evidence supports a switch from daily to weekly cholecalciferol dosing; however, weekly supplementation was not demonstrably worse at repleting levels and decreased a patient's daily pill burden.
Bortolussi-Courval É et al. · Basic & clinical pharmacology & toxicology (2024)
Limited direct evidence supports a switch from daily to weekly cholecalciferol dosing; however, weekly supplementation was not demonstrably worse at repleting levels and decreased a patient's daily pill burden.
8Weight lossMeta-AnalysisCited 43×n=947 · large study2019
Conclusions: This meta-analysis lays the foundation for defining the potential clinical efficacy of vitamin D supplementation as a potential therapeutic option for weight loss programs, but further studies are needed to confirm the validity of these findings and delineate potential underlying mechanisms.
Perna S · Medicina (Kaunas, Lithuania) (2019)
The selected articles focused on vitamin D supplementation in overweight and obese individuals with different conditions.
Eleven RCTs were included into this meta-analysis with a total of 947 subjects, with a mean of the follow-up from 1 to 12 months and different vitamin D interventions (from 25,000 to 600,000 IU/monthly of cholecalciferol).
9Pain controlMeta-AnalysisCited 27×n=570 · large study2017
The results of this study indicate that vitamin D supplementation may not have a clinically significant effect on pain control or structure progression among patients with knee OA.
Diao N et al. · Clinical biochemistry (2017)
Noticeable benefit
← WorseNo effectBetter →
The results indicated that vitamin D supplementation had a statistically significant but small-to-moderate effect on pain control in patients with knee OA (SMD=-0.32, 95% CI: -0.63 to -0.02).
However, no effects were observed for the change in tibial cartilage volume (SMD=0.12, 95% CI: -0.05 to 0.29) or joint space width (SMD=0.07, 95% CI: -0.08 to 0.23).
Longer-term clinical trials with rigorous measurement of symptom and radiologic changes are required to further clarify the effect of vitamin D supplementation in patients with symptomatic knee OA and low serum 25(OH)D levels.
10Follicular developmentMeta-AnalysisCited 70×n=502 · large study2017
Evidence from available RCTs suggests vitamin D supplementation may be beneficial for follicular development and menstrual cycle regulation in patients with PCOS.
Fang F et al. · Complementary therapies in clinical practice (2017)
Huge harm
← WorseNo effectBetter →
Vitamin D supplementation had significant effect on the improvement of follicular development with a higher number of dominant follicles (OR, 2.34; 95% CI, 1.39 to 3.92).
Differences in regular menstrual cycles were also observed when metformin plus vitamin D was compared with metformin alone (OR, 1.85; 95% CI, 1.01 to 3.39).
Evidence from available RCTs suggests vitamin D supplementation may be beneficial for follicular development and menstrual cycle regulation in patients with PCOS.
Conclusions: The study results suggest that vitamin D supplementation alleviates allergic rhinitis symptoms, although the effects differ according to the patient's sex and concomitant medications.
Kawada K et al. · Medicina (Kaunas, Lithuania) (2025)
No clear effect
← WorseNo effectBetter →
Likely real
Compared with placebos, vitamin D supplementation alleviated allergic rhinitis symptoms, although the difference was not significant; there was significant heterogeneity among studies (standardized mean difference [SMD] = -2.69, 95% confidence interval [CI]: -6.20 to 0.82, I2 = 98%, p < 0.01).
The proportion of female participants in the RCTs (slope: 0.21, p = 0.026) and concomitant corticosteroid use (slope: -9.16, p = 0.005) influenced the vitamin D response.
Compared with the placebos, vitamin D supplementation without corticosteroids alleviated the allergic rhinitis symptoms (SMD = -0.56, 95% CI: -0.90 to -0.23).
Results for main outcome (n = 53,235) revealed a positive effect of vitamin D on depressive symptoms (Hedges' g = -0.317, 95% CI [-0.405, -0.230], p < 0.001, I2 = 88.16%; GRADE: very low certainty).
Mikola T et al. · Critical reviews in food science and nutrition (2023)
Noticeable benefit
← WorseNo effectBetter →
Likely real
Results for main outcome (n = 53,235) revealed a positive effect of vitamin D on depressive symptoms (Hedges' g = -0.317, 95% CI [-0.405, -0.230], p < 0.001, I2 = 88.16%; GRADE: very low certainty).
Notwithstanding high heterogeneity, vitamin D supplementation ≥ 2,000 IU/day appears to reduce depressive symptoms.
Future research should investigate possible benefits of augmenting standard treatments with vitamin D in clinical depression.
15Serum 25-hydroxyvitamin D concentrationMeta-AnalysisCited 30×2024
Vitamin D3 leads to a greater increase of 25(OH)D than vitamin D2, even if limited to daily dose studies, but vitamin D2 and vitamin D3 had similar positive impacts on their corresponding 25(OH)D hydroxylated forms.
van den Heuvel EG et al. · Advances in nutrition (Bethesda, Md.) (2024)
Body mass index (BMI) appeared to be the strongest response modifier, reducing heterogeneity to 0% in both subgroups.
The vitamin D2- and vitamin D3-induced change in total 25(OH)D lost significance predominantly in subjects with a BMI >25 kg/m2 (P = 0.99).
Vitamin D3 leads to a greater increase of 25(OH)D than vitamin D2, even if limited to daily dose studies, but vitamin D2 and vitamin D3 had similar positive impacts on their corresponding 25(OH)D hydroxylated forms.
16Vitamin D status optimization in PCOSMeta-AnalysisCited 4×2024
Women with PCOS are responsive to vitamin D supplementation, but the benefit of providing doses of >3000 IU/day appears minimal.
Cochrane KM et al. · Nutrition reviews (2024)
Women with PCOS are responsive to vitamin D supplementation, but the benefit of providing doses of >3000 IU/day appears minimal.
Further data is required to determine dose-response at doses of >5000 IU/day, and whether higher intakes provide a clinically meaningful advantage in this population.
17Nephropathy risk in diabetic patientsMeta-AnalysisCited 45×n=219 · medium study2015
This meta-analysis showed the higher risk for nephropathy in vitamin D-deficient patients with diabetes.
Derakhshanian H et al. · Nutrition (Burbank, Los Angeles County, Calif.) (2015)
Huge harm
← WorseNo effectBetter →
Likely real
The pooled odds ratio from six cross-sectional studies was 1.80 (95% confidence interval [CI], 1.25-2.59; P = 0.002), indicating a significant inverse association between serum vitamin D status and risk for nephropathy in patients with diabetes.
However, the pooled data of UACR levels in clinical trials suggested no significant change following vitamin D supplementation (17.98; 95% CI, -35.35 to 71.32; P = 0.51).
This meta-analysis showed the higher risk for nephropathy in vitamin D-deficient patients with diabetes.
18Hip and nonvertebral fracture riskMeta-AnalysisCited 982×n=9,294 · very large study2005
Oral vitamin D supplementation between 700 to 800 IU/d appears to reduce the risk of hip and any nonvertebral fractures in ambulatory or institutionalized elderly persons.
Bischoff-Ferrari HA et al. · JAMA (2005)
Oral vitamin D supplementation between 700 to 800 IU/d appears to reduce the risk of hip and any nonvertebral fractures in ambulatory or institutionalized elderly persons.
An oral vitamin D dose of 400 IU/d is not sufficient for fracture prevention.
19Serum 25(OH)D levels at 8 weeksMeta-AnalysisCited 14×n=20 · very small study2020
We included three RCTs of varying quality.
Soe HHK et al. · The Cochrane database of systematic reviews (2020)
Noticeable benefit
← WorseNo effectBetter →
Vitamin D supplementation probably led to higher serum 25(OH)D levels at eight weeks, mean difference (MD) 29.79 (95% confidence interval (CI) 26.63 to 32.95); at 16 weeks, MD 12.67 (95% CI 10.43 to 14.90); and at 24 weeks, MD 15.52 (95% CI 13.50 to 17.54) (moderate-quality evidence).
There was little or no difference in adverse events (tingling of lips or hands) between the vitamin D and placebo groups, risk ratio 3.16 (95% CI 0.14 to 72.84) (low-quality evidence).
When comparing oral vitamin D 100,000 IU/month to 12,000 IU/month, the higher dose may have resulted in higher serum 25(OH)D levels at one year, MD 16.40 (95% CI 12.59 to 20.21) and at two years, MD 18.96 (95% CI 15.20 to 22.72) (low-quality evidence).
Although, serum 25(OH)D concentrations after supplementation reached sufficiency was observed, muscle strength did not significantly improve at this point of current meta-analysis.
Han Q et al. · Journal of the International Society of Sports Nutrition (2019)
No clear effect
← WorseNo effectBetter →
Could be chance
One repetition maximum Bench Press (1-RM BP) was not improved significantly (SMD 0.07, 95% CI: - 0.32 to 0.47, P = 0.72) and there was no significant increase in maximal quadriceps contraction (SMD -2.14, 95% CI: - 4.87 to 0.59, P = 0.12).
Furthermore, there was no significant overall effect of vitamin D3 intervention on muscle strength in this meta-analysis (SMD -0.75, 95% CI: - 1.82 to 0.32, P = 0.17).
Although, serum 25(OH)D concentrations after supplementation reached sufficiency was observed, muscle strength did not significantly improve at this point of current meta-analysis.