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Head-to-head evidence comparison — which supplement is right for you?
Vitamin D3 wins 2 of 3 categories. Both are solid choices — the best pick depends on your specific goals.
Verdict
Probably helps
18 of 30 studies with measurable effects showed benefit.
Top outcomes
Verdict
Likely helps
12 of 15 studies with measurable effects showed benefit.
Top outcomes
Shared outcomes (2)
Outcomes where both Vitamin D3 and Vitamin K2 have evidence — compare verdict strength side-by-side.
2000-4000 IU daily
Morning with breakfast
D3 (cholecalciferol) softgel or liquid
100-200mcg (MK-7)
With a meal containing fat
MK-7 (menaquinone-7)
K2 prevents arterial calcification while enhancing bone mineralization from vitamin D
ESSENTIAL PAIR. Take together to prevent arterial calcium deposition.
4-8 weeks
4-8 weeks
2-4 weeks
4-8 weeks
6-12 months
1-3 years
Vitamin D supplementation vs. placebo and incident type 2 diabetes in an ancillary study of the randomized Vitamin D and Omega-3 Trial
Nature communications (2025) · Meta analysis · n=5205
Mean body mass index (BMI) was 27.5 kg/m2 (SD = 5.3), with 51% female and 17% Black race/ethnicity.
Vitamin D Supplementation for Patients with Dysmenorrhoea: A Meta-Analysis with Trial Sequential Analysis of Randomised Controlled Trials
Nutrients (2024) · Meta analysis · n=687
TSA revealed that the current RCTs provide sufficient information.
Vitamin D and respiratory tract infections
BMJ (2017) · Meta analysis · n=11321
12% reduction in respiratory infections overall
Vitamins K2 and D3 Improve Long COVID, Fungal Translocation, and Inflammation: Randomized Controlled Trial
Nutrients (2025) · Rct · n=151
The median age was 46 years; 71% were female and 29% were non-white.
The effect of vitamin K2 supplementation on bone turnover biochemical markers in postmenopausal osteoporosis patients: a systematic review and meta-analysis
Frontiers in endocrinology (2025) · Meta analysis · n=2570
Vitamin K2 (VK2) increased osteocalcin (OC; MD 1.86, 95% CI 1.17-2.56) and bone-specific alkaline phosphatase (BAP; MD 1.49, 95% CI 0.98-2.00).
Vitamin K2 in Managing Nocturnal Leg Cramps: A Randomized Clinical Trial
JAMA internal medicine (2024) · Rct · n=310
Of the 199 enrolled individuals, 108 (54.3%) were female, and the mean (SD) age was 72.3 (5.5) years.
Meta-analysis showed 12% overall reduction in respiratory infections, with greater benefits in severely deficient individuals. Daily dosing more effective than bolus. Conservative estimate assumes most users not severely deficient.
Based on meta-analyses showing 2.17% WMD improvement in lumbar BMD. Effects primarily demonstrated with MK-7 form in postmenopausal women. Combination with vitamin D3 may enhance effects.
AI-estimated from published studies. Interpret as directional guidance.
Vitamin D3 has a higher evidence score (7.5/10 vs 6/10) and wins in 2 of 3 categories.
For bone health, Vitamin D3 has a higher relevance score (92 vs 88).
Vitamin D3 and Vitamin K2 may work well together: K2 prevents arterial calcification while enhancing bone mineralization from vitamin D ESSENTIAL PAIR. Take together to prevent arterial calcium deposition.