Vitamin D and Improved Vitamin D Levels

Research synthesisModerate evidenceModerate effect3 studies · 3 beneficial · 0 neutral · 0 harmful

Across all 3 studies, vitamin D supplementation showed moderate beneficial effects on improving vitamin D levels. The highest-quality study (a 2024 meta-analysis) reported a moderate effect (MD 15.55 ng/mL) for high-dose (5000-7943 IU/day) versus moderate-dose (800-2000 IU/day) vitamin D in adults undergoing bariatric surgery. One RCT found maternal supplementation with 15,000 IU/week led to higher infant 25(OH)D at 12 months. Median study duration was 365 days (1 study).

Effective dose range: 5000-7943 IU/day (high-dose range, based on meta-analysis comparison) or 15,000 IU/week (about 2143 IU/day in the RCT)
Studied populations: adults with obesity undergoing bariatric surgery; lactating mothers and their infants

Caveats: Evidence base is small (only 3 studies) — conclusions should be considered preliminary. Available evidence is overwhelmingly positive — clinical literature in this area is subject to publication bias (null-result studies are less likely to be published or indexed). Two of the three studies focused on specific clinical populations (post-bariatric surgery, lactating mothers in Ethiopia) — generalizability to the general population may be limited.

Generated Jul 12, 2026

Doses used in studies

IU/day: 5,000–7,943 (median 6,471.5, IQR 5,000–7,943) — 1 study
IU/week: 15,000 (median 15,000, IQR 15,000–15,000) — 1 study

Time to effect

Median: 12.2 months · IQR 12.2 months–12.2 months · Range 12.2 months–12.2 months — Reported in 1 of 3 studies

Safety in these studies

adverse eventsReported
The trial reported no adverse events in the moderate-dose vitamin D arm, but did not provide any information on adverse events in the placebo arm.
from: Oral vitamin D supplementation for adults with obesity undergoing bariatric surgery.

3 of 3 papersPopulation:

Oral vitamin D supplementation for adults with obesity undergoing bariatric surgery.
- 2024-10-01
- Meta-Analysis · n = 314
- The Cochrane database of systematic reviews 2024(10)
- - Marlene T Chakhtoura
  - Nancy F Nakhoul
  - Elie A Akl
  - Bassem Y Safadi
  - Christos S Mantzoros
  - Maria-Inti Metzendorf
  - Ghada El-Hajj Fuleihan
- PubMed: 39351881
- DOI: 10.1002/14651858.cd011800.pub2
4 Insights on
- Improved Vitamin D Levels
- High evidence
- Clinical
High-dose vitamin D may increase 25-hydroxyvitamin D levels compared to a moderate dose at 12 months (MD 15.55 ng/mL, 95% CI 3.50 to 27.61)
Effect
Beneficial
Effect size
Moderate
Significant
Yes
Dose
high-dose (equivalent >3500 IU/day, range 5000-7943 IU/day) vs moderate-dose (800-2000 IU/day)
Effects of weekly cholecalciferol supplementation of lactating mothers on vitamin D status, and infant growth and gross motor development: a randomized controlled trial in rural Ethiopia.
- 2025-11
- RCT
- The American journal of clinical nutrition 122(5)
- - Meron Girma
  - Alemayehu Argaw
  - Birkneh Tilahun Tadesse
  - Biruk Mulugeta
  - Winyoo Chowanadisai
  - Barbara J Stoecker
- PubMed: 40754215
- DOI: 10.1016/j.ajcnut.2025.07.028
4 Insights on
- Improved Vitamin D Levels
- High evidence
- Infants
Maternal vitamin D supplementation also led to significantly higher infant plasma 25(OH)D concentration at 12 mo compared with the placebo group [14.7 nmol/L (95% CI: 5.29, 24.1 nmol/L; P = 0.003)]
Effect
Beneficial
Effect size
Moderate
Significant
Yes
Dose
15,000 IU/week
Health Benefits of Bread Fortification: A Systematic Review of Clinical Trials according to the PRISMA Statement.
- 2023-10-20
- Systematic Review
- Nutrients 15(20)
- - Urszula Kaim
  - Zuzanna Sabina Goluch
- PubMed: 37892534
- DOI: 10.3390/nu15204459
8 Insights on
- Improved Vitamin D Levels
- High evidence
- Rigorous Journal
Clinical trials have shown health benefits from consuming bread fortified with vitamins (B9, C, D2, D3), minerals (K, P, Ca, Mg, Fe, Zn, Cr, Se), fiber, proteins, and polyphenolic compounds.
Effect
Beneficial
Effect size
Moderate
Significant
Yes
Dose
not stated

Vitamin D and Improved Vitamin D Levels

Oral vitamin D supplementation for adults with obesity undergoing bariatric surgery.

Effects of weekly cholecalciferol supplementation of lactating mothers on vitamin D status, and infant growth and gross motor development: a randomized controlled trial in rural Ethiopia.

Health Benefits of Bread Fortification: A Systematic Review of Clinical Trials according to the PRISMA Statement.