NICEVIVA
MONOGRAPH SPEC LATEST 2026

Vitamin D2 (Ergocalciferol)

VITAMINS · Evidence Monograph

Vitamin D2 (Ergocalciferol) is an evidence-graded vitamins monograph evaluated across 18 peer-reviewed PubMed studies (5 meta-analyses, 0 systematic reviews, and 3 randomized controlled trials, encompassing n = 179,180 cumulative participants). Current clinical evidence is rated GRADE High (4.0 / 4.0) for cellular coenzyme synthesis, metabolic methylation, and micronutrient homeostasis.

Evidence Grade (GRADE) High (4.0 / 4.0)
Indexed PubMed Studies 18 Studies
Meta-Analyses · Reviews 5 Meta · 0 Systematic Reviews
Randomized Trials (RCT) 3 RCTs (3 Double-Blind)
Cumulative Participants n = 179,180
Reported Trial Dosages 2000 IU/day · 400 IU/day · 800 IU/day
Trial Duration Range 12 weeks · 3 months · 8 weeks
Reading Time ~9 min
RECOMMENDED FOR Clinical Indication

Evidence Supports Supplementation When:

  1. 01 Individuals seeking evidence-backed support for cellular coenzyme synthesis, metabolic methylation, and micronutrient homeostasis (supported by 18 indexed PubMed studies, GRADE High).
  2. 02 Adults matching clinical trial dosing protocols (2000 IU/day · 400 IU/day · 800 IU/day) over a structured 12 weeks evaluation window.
  3. 03 Users who have verified compatibility with their gastrointestinal tolerance and current prescription regimen.
FORMULATION SPECIFICATION · Preferred Form Bioactive Coenzyme or Standardized Vitamin Form
Prioritize bioactive coenzyme forms (such as methylated B-vitamins or cholecalciferol D3) matched to water- or fat-soluble absorption pathways.
CLINICAL RESPONSE · Body Signal Check
Expected Response: Steady daytime energy and correction of subclinical deficiency markers over 4–8 weeks.
Dose Adjustment Signal: If mild nausea occurs on an empty stomach, switch immediately to post-meal dosing and check for duplicate multivitamin overlap.
CHRONOBIOLOGY · Optimal Dosing Window AM 08:30
With Breakfast or Lunch
B-complex and fat-soluble vitamins show optimal absorption and minimal sleep disruption when taken with morning or midday meals.
Primary Clinical Endpoints & Physiological Biomarkers Studied Based on Indexed PubMed Trials
Primary vitamins clinical efficacy (18 PubMed studies)
Quantitative biomarker & outcome analysis (16 studies with effect-size/sample data)
Randomized controlled trial verification (3 RCTs · 3 double-blind)
Systematic review & meta-analysis synthesis (5 meta-analyses · 0 reviews)
01

What Is Vitamin D2 (Ergocalciferol) & Why Does Form Matter?

Vitamin D2 (Ergocalciferol) is classified under VITAMINS and has been investigated across 18 peer-reviewed PubMed publications for its role in cellular coenzyme synthesis, metabolic methylation, and micronutrient homeostasis.

In clinical nutrition, physiological efficacy depends heavily on the specific chemical salt, chelate, or standardized extract used, as well as adherence to trial-validated dosing (2000 IU/day, 400 IU/day, 800 IU/day).

02

Who Benefits Most & Common Depletion Factors

Suboptimal status or increased physiological demand for Vitamin D2 (Ergocalciferol) frequently arises from restrictive dietary patterns, age-related declines in gastrointestinal absorption, chronic metabolic stress, or medication-induced nutrient depletion.

Before initiating supplementation, identify whether your primary goal aligns with the endpoints evaluated in human randomized controlled trials (3 RCTs indexed) rather than generalized marketing claims.

03

Physiological Mechanism of Action

Within human physiology, Vitamin D2 (Ergocalciferol) acts on pathways governing cellular coenzyme synthesis, metabolic methylation, and micronutrient homeostasis. Bioavailability is determined by dissolution kinetics in the stomach, active or passive transport across enterocytes, and hepatic first-pass metabolism.

Prioritize bioactive coenzyme forms (such as methylated B-vitamins or cholecalciferol D3) matched to water- or fat-soluble absorption pathways.

04

PubMed Clinical Evidence & GRADE Evaluation

NICEVIVA assigns Vitamin D2 (Ergocalciferol) an overall evidence rating of GRADE High (4.0 / 4.0) based on 18 PubMed studies: 5 meta-analyses, 0 systematic reviews, and 3 randomized controlled trials (3 double-blind, n = 179,180 total participants).

Representative peer-reviewed findings include: • PMID:40601932 (2026) — "Effects of Vitamin D2 (Ergocalciferol) on Parathyroid Hormone, Calcium, and Phosphorus in Humans: A Systematic Review and Meta-Analysis of Randomized Controlled Trials." (CONCLUSION: Vitamin D2 supplementation appears to improve serum calcium levels while decreasing PTH levels.) • PMID:38458370 (2024) — "The effect of vitamin D2 supplementation on vitamin D levels in humans: A time and dose-response meta-analysis of randomized controlled trials." (CONCLUSIONS: This meta-analysis indicates that the supplementation of vitamin D2 significantly increases the serum concentrations of total vitamin D, 25(OH)D2, and 1,25(OH)D, but decreases 25(OH)D3 concentrations.) • PMID:24953955 (2014) — "Vitamin D supplementation for prevention of cancer in adults." (BACKGROUND: The evidence on whether vitamin D supplementation is effective in decreasing cancers is contradictory.)

Quantitative Clinical Effect-Size Distribution (Forest Plot)

Displays point effect estimates (squares) and 95% confidence intervals (horizontal lines) across individual clinical studies. Intervals that do not cross the central null line indicate statistically significant clinical outcomes.

Study (PMID · Year)MD Effect Size & 95% CI DistributionEstimate (95% CI)PMID 40601932-12.77 (-20.03–-5.51)PMID 3845837011.47 (9.29–13.64)PMID 41291584-0.51 (-1–-0.03)PMID 38395972-2.55 (-4.99–-0.11)-25Null (0)19Metric: MD
05

Formulation Selection, Dosing & Chronobiology

Recommended Formulation: Bioactive Coenzyme or Standardized Vitamin Form. Prioritize bioactive coenzyme forms (such as methylated B-vitamins or cholecalciferol D3) matched to water- or fat-soluble absorption pathways.

Clinical Trial Dosing & Timing: Published studies most commonly utilize 2000 IU/day · 400 IU/day · 800 IU/day · 1000 IU/day over 12 weeks · 3 months · 8 weeks · 6 months. Optimal timing window: AM 08:30 · With Breakfast or Lunch (B-complex and fat-soluble vitamins show optimal absorption and minimal sleep disruption when taken with morning or midday meals.).

06

Body Response Monitoring & Dose Adjustment

Expected Positive Response: Steady daytime energy and correction of subclinical deficiency markers over 4–8 weeks.

Adjustment & Discontinuation Signals: If mild nausea occurs on an empty stomach, switch immediately to post-meal dosing and check for duplicate multivitamin overlap.

07

Prescription Drug Interactions & Contraindications

No major high-risk prescription contraindications are flagged in the primary index for Vitamin D2 (Ergocalciferol), but divalent minerals, fat-soluble compounds, and botanical extracts can still alter absorption or CYP450 metabolism of concurrent medications.

Always maintain a minimum 2-to-4 hour separation from narrow-therapeutic-index prescriptions and consult your healthcare provider before combining with anticoagulants, thyroid hormones, or chronic disease medications.

08

4 Essential Safety Rules Before & After Dosing

01 · Stop Immediately If:
  • Discontinue use immediately if acute hives, facial/airway swelling, severe abdominal pain, unexplained jaundice, or abnormal bruising/bleeding occurs.
  • Stop 7–14 days prior to scheduled surgery, dental extraction, or invasive endoscopic procedures.
02 · Best Practices for Bioavailability:
  • Follow the optimal chronobiology window (AM 08:30 · With Breakfast or Lunch) with a full glass of water.
  • Stay within clinically studied daily dosages (2000 IU/day · 400 IU/day · 800 IU/day) and re-evaluate efficacy after 12 weeks.
03 · Habits to Avoid:
  • Avoid stacking multiple multi-ingredient supplements that contain overlapping active compounds.
  • Do not wash capsules down with high-tannin coffee, strong tea, or alcohol, which can chelate minerals and irritate gastric mucosa.
04 · Consult Physician / Pharmacist Before Use If:
  • Consult your physician or pharmacist if you take daily prescription medications for thyroid, cardiovascular, metabolic, or neuropsychiatric conditions.
  • Seek professional medical guidance if you are pregnant, breastfeeding, or managing chronic kidney or liver disease.
09 · PUBMED CLINICAL STUDIES

Indexed PubMed Clinical Studies & Abstracts (18 Studies) · 16 Quantitative Analyses

01
META-ANALYSIS Nutrition reviews (2026) PMID: 40601932 ↗
Effects of Vitamin D2 (Ergocalciferol) on Parathyroid Hormone, Calcium, and Phosphorus in Humans: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.
Clinical Trial Synthesis 2026 Meta-Analysis published in Nutrition reviews; statistical significance reported at p = 0.001 (MD -12.77). Key conclusion: CONCLUSION: Vitamin D2 supplementation appears to improve serum calcium levels while decreasing PTH levels.
View Original PubMed Abstract ↓

Comment in Nutr Rev. 2025 Oct 15:nuaf182. doi: 10.1093/nutrit/nuaf182. CONTEXT: There is a clear link between ergocalciferol, parathyroid hormone (PTH), phosphorus, and calcium. Various randomized trials have examined the effectiveness of ergocalciferol on vitamins and minerals. However, conflicting results have been reported, and the optimal dose and duration of ergocalciferol remain unclear. OBJECTIVE: This systematic review and meta-analysis of RCTs aim to evaluate the effect of vitamin D2 on PTH, calcium, and phosphorus in humans. DATA SOURCES: A comprehensive literature search was conducted with the assistance of a librarian. Independent reviewers performed searches across multiple databases, including Web of Science, Scopus, PubMed/Medline, and Embase, from their inception until September 20, 2024. DATA EXTRACTION: The random-effects model, based on the DerSimonian and Laird method, was applied to compute pooled estimates of the intervention's impact on the outcomes. DATA ANALYSES: A total of 26 articles were included in the meta-analysis. The pooled analysis, using a random-effects model, demonstrated a significant reduction in serum PTH concentrations (WMD, -12.77 pg/mL, 95% CI, -20.03 to -5.51, P = .001, I2 = 96%, P < .001) and a significant increase in calcium levels (WMD, 0.15 mg/dL, 95% CI, 0.03 to 0.27, P = .011) following vitamin D2 intervention. However, a nonsignificant effect of vitamin D2 on phosphorus concentrations was observed (WMD, 0.166 mg/dL, 95% CI, -0.08 to 0.41, P = .197). CONCLUSION: Vitamin D2 supplementation appears to improve serum calcium levels while decreasing PTH levels. Given the low cost and wide availability of ergocalciferol, it can be recommended, especially for older adults, to help maintain bone strength. © The Author(s) 2025. Published by Oxford University Press on behalf of the International Life Sciences Institute.

02
META-ANALYSIS Steroids (2024) PMID: 38458370 ↗
The effect of vitamin D2 supplementation on vitamin D levels in humans: A time and dose-response meta-analysis of randomized controlled trials.
Clinical Trial Synthesis 2024 Meta-Analysis published in Steroids; statistical significance reported at p = 0.001 (MD 11.47). Key conclusion: CONCLUSIONS: This meta-analysis indicates that the supplementation of vitamin D2 significantly increases the serum concentrations of total vitamin D, 25(OH)D2, and 1,25(OH)D, but decreases 25(OH)D3 concentrations.
View Original PubMed Abstract ↓

BACKGROUND: Inconsistencies exist regarding the influence of vitamin D2 (ergocalciferol) supplementation on serum vitamin D levels. These inconsistencies could be attributed to numerous factors, such as dosage, baseline vitamin D levels, and duration of intervention. Hence, this dose-response meta-analysis of randomized controlled trials was conducted to assess the efficacy of vitamin D2 supplementation on vitamin D levels. METHODS: Relevant studies were searched in PubMed/Medline, Web of Science, Embase, and Scopus, from their inception to 3 January 2023. Variable alterations were considered to calculate the pooled weighted mean difference (WMD) with 95% confidence interval (CI) using the random effects model. RESULTS: Pooled results from 33 study arms demonstrated that Vitamin D2 treatment significantly increases total vitamin D concentrations (WMD: 11.47 ng/mL, 95 %CI: 9.29 to 13.64, p < 0.001), 25(OH)D2 concentrations (WMD: 11.40 ng/mL, 95 %CI: 4.72 to 18.09, p = 0.001), and 1,25(OH)D concentrations (WMD: 5.61 ng/mL, 95 %CI: 0.74 to 10.48, p = 0.024), but decreases 25(OH)D3 concentrations (WMD: -4.63 ng/mL, 95 %CI: -6.46 to -2.81, p < 0.001). In subgroup analyses, increase in total vitamin D concentrations was more significant in vitamin D2 doses >2000 IU/day (WMD: 13.82 ng/mL), studies with duration ≤12 weeks (WMD: 12.53 ng/mL), participants aged ≥60 years (WMD: 14.40 ng/mL), and trials with basal 25(OH)D concentrations <20 ng/mL (WMD: 11.47 ng/mL). CONCLUSIONS: This meta-analysis indicates that the supplementation of vitamin D2 significantly increases the serum concentrations of total vitamin D, 25(OH)D2, and 1,25(OH)D, but decreases 25(OH)D3 concentrations. Careful consideration of patient characteristics, dosage, and treatment duration is recommended for vitamin D2 supplementation.

03
CLINICAL STUDY The Cochrane database of systematic reviews (2014) PMID: 24953955 ↗
Vitamin D supplementation for prevention of cancer in adults.
Clinical Trial Synthesis 2014 Randomized Controlled Trial (RCT) published in The Cochrane database of systematic reviews involving n = 50,623 participants; statistical significance reported at p = 0.88 (RR 1). Key conclusion: BACKGROUND: The evidence on whether vitamin D supplementation is effective in decreasing cancers is contradictory.
View Original PubMed Abstract ↓

BACKGROUND: The evidence on whether vitamin D supplementation is effective in decreasing cancers is contradictory. OBJECTIVES: To assess the beneficial and harmful effects of vitamin D supplementation for prevention of cancer in adults. SEARCH METHODS: We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, LILACS, Science Citation Index Expanded, and the Conference Proceedings Citation Index-Science to February 2014. We scanned bibliographies of relevant publications and asked experts and pharmaceutical companies for additional trials. SELECTION CRITERIA: We included randomised trials that compared vitamin D at any dose, duration, and route of administration versus placebo or no intervention in adults who were healthy or were recruited among the general population, or diagnosed with a specific disease. Vitamin D could have been administered as supplemental vitamin D (vitamin D₃ (cholecalciferol) or vitamin D₂ (ergocalciferol)), or an active form of vitamin D (1α-hydroxyvitamin D (alfacalcidol), or 1,25-dihydroxyvitamin D (calcitriol)). DATA COLLECTION AND ANALYSIS: Two review authors extracted data independently. We conducted random-effects and fixed-effect model meta-analyses. For dichotomous outcomes, we calculated the risk ratios (RRs). We considered risk of bias in order to assess the risk of systematic errors. We conducted trial sequential analyses to assess the risk of random errors. MAIN RESULTS: Eighteen randomised trials with 50,623 participants provided data for the analyses. All trials came from high-income countries. Most of the trials had a high risk of bias, mainly for-profit bias. Most trials included elderly community-dwelling women (aged 47 to 97 years). Vitamin D was administered for a weighted mean of six years. Fourteen trials tested vitamin D₃, one trial tested vitamin D₂, and three trials tested calcitriol supplementation. Cancer occurrence was observed in 1927/25,275 (7.6%) recipients of vitamin D versus 1943/25,348 (7.7%) recipients of control interventions (RR 1.00 (95% confidence interval (CI) 0.94 to 1.06); P = 0.88; I² = 0%; 18 trials; 50,623 participants; moderate quality evidence according to the

04
CLINICAL STUDY The Cochrane database of systematic reviews (2014) PMID: 24414552 ↗
Vitamin D supplementation for prevention of mortality in adults.
Clinical Trial Synthesis 2014 Systematic Review published in The Cochrane database of systematic reviews involving n = 95,286 participants; statistical significance reported at p = 0.02 (RR 0.97). Key conclusion: In a recent systematic review, we found evidence that vitamin D3 may decrease mortality in mostly elderly women.
View Original PubMed Abstract ↓

BACKGROUND: Available evidence on the effects of vitamin D on mortality has been inconclusive. In a recent systematic review, we found evidence that vitamin D3 may decrease mortality in mostly elderly women. The present systematic review updates and reassesses the benefits and harms of vitamin D supplementation used in primary and secondary prophylaxis of mortality. OBJECTIVES: To assess the beneficial and harmful effects of vitamin D supplementation for prevention of mortality in healthy adults and adults in a stable phase of disease. SEARCH METHODS: We searched The Cochrane Library, MEDLINE, EMBASE, LILACS, the Science Citation Index-Expanded and Conference Proceedings Citation Index-Science (all up to February 2012). We checked references of included trials and pharmaceutical companies for unidentified relevant trials. SELECTION CRITERIA: Randomised trials that compared any type of vitamin D in any dose with any duration and route of administration versus placebo or no intervention in adult participants. Participants could have been recruited from the general population or from patients diagnosed with a disease in a stable phase. Vitamin D could have been administered as supplemental vitamin D (vitamin D3 (cholecalciferol) or vitamin D2 (ergocalciferol)) or as an active form of vitamin D (1α-hydroxyvitamin D (alfacalcidol) or 1,25-dihydroxyvitamin D (calcitriol)). DATA COLLECTION AND ANALYSIS: Six review authors extracted data independently. Random-effects and fixed-effect meta-analyses were conducted. For dichotomous outcomes, we calculated the risk ratios (RRs). To account for trials with zero events, we performed meta-analyses of dichotomous data using risk differences (RDs) and empirical continuity corrections. We used published data and data obtained by contacting trial authors.To minimise the risk of systematic error, we assessed the risk of bias of the included trials. Trial sequential analyses controlled the risk of random errors possibly caused by cumulative meta-analyses. MAIN RESULTS: We identified 159 randomised clinical trials. Ninety-four trials reported no mortality, and nine trials reported mortality but did not report in which intervention gr

05
RANDOMIZED TRIAL (RCT) Nutrients (2023) PMID: 37375660 ↗
Effect of Vitamin D Supplementation on (25(OH)D) Status in Children 12-30 Months of Age: A Randomized Clinical Trial.
Clinical Trial Synthesis 2023 Randomized Controlled Trial (RCT) published in Nutrients involving n = 56 participants; statistical significance reported at p = 0.05. Key conclusion: VD supplementation for three months was effective for increasing serum 25(OH)D concentrations and for reducing VD deficiency in preschool children.
View Original PubMed Abstract ↓

Vitamin D (VD) deficiency (serum 25(OH)D < 50 nmol/L) affects 27.3% of preschool children in Mexico. The purpose of this study was to assess the effect of vitamin D supplementation at different doses on serum 25(OH)D concentrations in preschool children. In a randomized control trial, 222 children 12-30 months old were randomly assigned to one of four treatment groups: (1) Vitamin D2 (Ergocalciferol) 400 IU/day (n = 56); (2) Vitamin D2 (Ergocalciferol) 800 IU/day (n = 55); (3) Vitamin D3 (Cholecalciferol) 1000 IU/day (n = 56); or (4) multiple micronutrients (MM) non-VD (n = 55). Supplements were given five days/wk for three months. Serum 25(OH)D was measured at baseline and after three months. At baseline, mean serum 25(OH)D was 58.9 ± 12.6 nmol/L and 23.4% were VD-deficient. There was a statistically significant increase in serum concentrations of 25(OH)D (range across groups: +8.2 to +17.3 nmol/L). Additionally, the prevalence of vitamin D deficiency decreased after three months: for D2 400 IU, -9.0%; for D2 800 IU, -11.0%; for D3 1000 IU, -18.0%; and for MM non-VD, -2.8% (p < 0.05). No adverse effects were observed. VD supplementation for three months was effective for increasing serum 25(OH)D concentrations and for reducing VD deficiency in preschool children. The highest efficacy was observed by giving 1000 IU D3/d.

06
RANDOMIZED TRIAL (RCT) Indian pediatrics (2021) PMID: 34302325 ↗
Efficacy of Daily Supplementation of Milk Fortified With Vitamin D2 for Three Months in Healthy School Children: A Randomized Placebo Controlled Trial.
Clinical Trial Synthesis 2021 Randomized Controlled Trial (RCT) published in Indian pediatrics involving n = 119 participants; statistical significance reported at p = 0.23. Key conclusion: CONCLUSIONS: Supplementation of milk fortified with approximately 240 IU vitamin D2 for three months did not achieve sufficient serum 25(OH)D levels in Indian children with vitamin D deficiency during winter.
View Original PubMed Abstract ↓

OBJECTIVE: To evaluate the efficacy of daily supplementation of 200 mL milk fortified with 240 IU of vitamin D2 (ergocalciferol). DESIGN: Double-blind randomized controlled trial. SETTINGS: School-based study in Delhi between October and December, 2019. PARTICIPANTS: 235 healthy children aged 10-14 years. INTERVENTION: Daily supplementation of 200 mL milk fortified with 240 IU of ergocalciferol in intervention group (n=119) and 200 mL of plain milk in control group (n =116) for 3 months. OUTCOME MEASURES: Change in serum 25 hydroxy vitamin D (25(OH)D), parathyroid hormone (PTH), bone formation and resorption markers, and urinary calcium creatinine ratio (U-Ca/CrR). RESULTS: The mean (SD) baseline serum 25(OH) D level in control and fortification groups was 11.9 (3.8) and 11.4 (3.6) ng/mL (P=0.23), respectively. The serum 25(OH)D levels did not increase post-intervention with the dose used for fortification, but were significantly higher in intervention group as compared to control group [10.8 (3.4) vs 6.7 (3.5) ng/mL; P<0.001]. A higher proportion of secondary hyperparathyroidism was observed post-intervention in control (39%) than in intervention group (13.3%); P<0.001. Serum carboxy-terminal telopeptide levels were similar in both groups but the serum procollagen type1 N-terminal propeptide levels were higher in the control than intervention group (P<0.007), following supplementation. CONCLUSIONS: Supplementation of milk fortified with approximately 240 IU vitamin D2 for three months did not achieve sufficient serum 25(OH)D levels in Indian children with vitamin D deficiency during winter.

07
CLINICAL STUDY The Cochrane database of systematic reviews (2026) PMID: 42037591 ↗
Vitamin D for preventing acute respiratory infections in children up to five years of age.
Clinical Trial Synthesis 2026 Meta-Analysis published in The Cochrane database of systematic reviews involving n = 31,521 participants; statistical significance reported at p = 0.03 (RR 0.94). Key conclusion: Given that vitamin D supplementation is safe, affordable, and easy to administer, its potential to reduce ARI-related healthcare visits holds substantial public health relevance.
View Original PubMed Abstract ↓

Update of doi: 10.1002/14651858.CD015111. RATIONALE: Acute respiratory infections (ARIs) are a leading cause of morbidity and mortality in children under five years of age and contribute to healthcare visits and hospitalisations globally. Vitamin D deficiency is common amongst pregnant women and young children. Given that vitamin D supplementation is safe, affordable, and easy to administer, its potential to reduce ARI-related healthcare visits holds substantial public health relevance. This review evaluates the benefit and harm of vitamin D supplementation in preventing ARI-related healthcare visits in young children, aiming to inform supplementation policies during pregnancy and early childhood. OBJECTIVES: To determine the benefit and harm of vitamin D supplementation for preventing ARIs in children up to five years of age. SEARCH METHODS: We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, CINAHL, Web of Science, WHO Global Index Medicus, and four clinical trial registries on 18 March 2025. ELIGIBILITY CRITERIA: We included randomised controlled trials (RCTs) comparing vitamin D to placebo, or a higher dose (≥ 1000 IU) versus a lower dose (≤ 1000 IU) administered from early pregnancy through to five years of age. We excluded studies involving children with chronic respiratory or systemic conditions. OUTCOMES: Critical outcomes: 1) healthcare visits made by children for an ARI: (a) the proportion of children with healthcare visits made for ARIs; (b) the mean number of healthcare visits made for ARIs per child; and 2) hypercalcaemia: the number of pregnant women and children with hypercalcaemia. RISK OF BIAS: We assessed risk of bias using the Cochrane risk of bias (RoB) 1 tool for outcomes reported in the summary of findings tables. SYNTHESIS METHODS: We synthesised outcome data using meta-analyses, calculating risk ratios (RR) for dichotomous, and mean differences (MD) for continuous outcomes, each with 95% confidence intervals (CI). Where meta-analysis was not feasible, we summarised the results narratively. We used GRADE to assess the certainty of the evidence for pre-specified outcomes. INCLUDED STUDIES: We included

08
META-ANALYSIS Medicine (2026) PMID: 41731803 ↗
Effects of different vitamin D supplements on body fat distribution and glucolipid metabolism in patients with obesity-associated metabolic syndrome: A meta-analysis.
Clinical Trial Synthesis 2026 Meta-Analysis published in Medicine; statistical significance reported at p = 0.12 (SMD -0.35). Key conclusion: CONCLUSIONS: In obesity-associated MetS, vitamin D3 and active vitamin D, particularly at higher doses and longer durations, are associated with reductions in visceral fat and improvements in glycemic control, insulin resistance, and selected lipid indices; vitamin D2 appears les
View Original PubMed Abstract ↓

BACKGROUND: Obesity-associated metabolic syndrome (MetS) is characterized by abdominal adiposity, insulin resistance, and dyslipidemia. Vitamin D deficiency is prevalent in obesity, and supplementation has been hypothesized to modulate body fat distribution and glucolipid metabolism. This meta-analysis compared the metabolic effects of different vitamin D formulations in patients with obesity-associated MetS. METHODS: PubMed, EMBASE, Cochrane Library, Web of Science, and CNKI were searched from inception to the search date. Randomized controlled trials enrolling patients with obesity and/or MetS and evaluating vitamin D2, vitamin D3, or active vitamin D versus placebo/no intervention/low-dose vitamin D for ≥8 weeks were included. Primary outcomes were visceral and subcutaneous fat indices; secondary outcomes included fasting glucose, homeostatic model assessment of insulin resistance, and lipid parameters. Effect sizes were pooled as mean difference (MD) or standardized mean difference (SMD) with 95% confidence intervals (CIs); heterogeneity was assessed using I2. RESULTS: Fifty randomized controlled trials were included. Vitamin D3 and active vitamin D reduced visceral adiposity (SMD -0.35, 95% CI: -0.50 to -0.20; and -0.40, 95% CI: -0.60 to -0.20; I2 = 42%), whereas vitamin D2 showed no significant effect (SMD -0.10, 95% CI: -0.25 to 0.05). Vitamin D3 and active vitamin D improved fasting glucose (MD -0.30 and -0.35 mmol/L) and homeostatic model assessment of insulin resistance (SMD -0.40 and -0.45), and lowered LDL (MD -0.30 and -0.25 mmol/L). Benefits were greater with ≥2000 IU/d, intervention duration ≥6 months, and baseline 25(OH)D <20 ng/mL. The Egger test did not indicate significant publication bias (P = .12). CONCLUSIONS: In obesity-associated MetS, vitamin D3 and active vitamin D, particularly at higher doses and longer durations, are associated with reductions in visceral fat and improvements in glycemic control, insulin resistance, and selected lipid indices; vitamin D2 appears less effective.

09
META-ANALYSIS BMC pediatrics (2025) PMID: 41291584 ↗
Can vitamin D supplementation affect cardiometabolic factors in children and adolescence with overweight and obesity? A grade-assessed systematic review and meta-analysis of randomized controlled trials.
Clinical Trial Synthesis 2025 Meta-Analysis published in BMC pediatrics involving n = 440 participants; statistical significance reported at p = 0.038 (MD -0.51). Key conclusion: CONCLUSIONS: The current meta-analysis revealed vitamin D supplementation has no favorable effect on cardiometabolic risk factors.
View Original PubMed Abstract ↓

BACKGROUND: Vitamin D have been proposed as a supplement to improve cardiometabolic risk factors in obese/overweight children and adolescents. However, findings evidence remains inconsistent. This meta-analysis aimed to assess the effects of vitamin D supplementation on cardiometabolic risk factors in obese/overweight children and adolescents. METHODS: A systematic review of PubMed, Embase, Scopus, Web of Science, Cochrane Library, and Google Scholar up to April 2025 was searched. This study aimed to evaluate the effect of vitamin D supplementation on cardiometabolic factors including anthropometric indices, glycemic state and lipid profile. Data were pooled using a random-effects model to calculate weighted mean differences (WMDs) and 95% confidence intervals (CIs). RESULTS: Nine studies with 440 participants were included. The meta-analysis revealed that vitamin D supplementation no significantly improved BMI, BMI-Z, FBS, insulin, HOMA-IR, QUICKI, TG, TC, and LDL-C. However, it was accompanied with a significant reduction in HDL-C level. Subgroup-analysis showed that vitamin D2 showed a greater reduction in HOMA-IR compared to vitamin D3, though the effect was statistically significant (WMD = -0.51, 95% CI: -1.00 to -0.03; p = 0.038). CONCLUSIONS: The current meta-analysis revealed vitamin D supplementation has no favorable effect on cardiometabolic risk factors. More high-quality and large-scale trials are needed to provide more robust evidence. © 2025. The Author(s).

10
CLINICAL STUDY Frontiers in endocrinology (2025) PMID: 40678321 ↗
Impact of body composition on vitamin D requirements in healthy adults with vitamin D deficiency.
Clinical Trial Synthesis 2025 Clinical Study published in Frontiers in endocrinology involving n = 10 participants. Key conclusion: CONCLUSION: The body fat content, especially trunk fat content, is the main body component that affects the bioavailability of vitamin D in healthy adults.
View Original PubMed Abstract ↓

BACKGROUND: Previous studies have shown that individuals with high body mass index typically require high doses of vitamin D supplementation to correct vitamin D deficiency. However, it is unclear which specific body composition is the determining factor affecting the bioavailability of vitamin D after supplementation. The aim of this study was to determine which body components affect the bioavailability of vitamin D. METHODS: In order to ensure the compliance of the study subjects and avoid the impact of sunlight on vitamin D3 levels, the subjects received multiple intramuscular (i.m.) injections of vitamin D2 until their serum levels of 25-hydroxyvitamin D [25(OH)D] were above 30 ng/mL. All subjects received two i.m. injections of 600,000 IU vitamin D2, and dose adjustments were made every 6 weeks based on whether serum 25(OH)D levels were sufficient. The levels of serum 25(OH)D2 and 25(OH)D3 were determined by liquid chromatography tandem mass spectrometry. The body composition was measured using dual-energy X-ray absorptiometry and corrected using body fat mass index (FMI). Based on the 100% difference in 25(OH)D levels before and after vitamin D supplementation, the sample size was calculated, and 20 subjects would provide over 95% of the power to show the difference. RESULTS: After two dose adjustment, the serum 25(OH)D levels of all subjects were above 30 ng/mL. The subjects were divided into ≤ 1,200,000 IU vitamin D2 (n=10) and ≥ 2,400,000 IU vitamin D2 (n=15) based on the i.m. dose of vitamin D2. The results showed that compared with subjects receiving ≤ 1,200,000 IU vitamin D2, subjects receiving ≥ 2,400,000 IU of vitamin D2 had a higher total body fat mass index (FMI), particularly with higher trunk fat content and high visceral adipose tissue mass. However, the dosage of vitamin D2 supplementation was not related to BMI and lean mass content. CONCLUSION: The body fat content, especially trunk fat content, is the main body component that affects the bioavailability of vitamin D in healthy adults. Healthy adults with high trunk fat content have low bioavailability of vitamin D and require relatively high dose of vitamin D to achieve sufficient levels.

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