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Head-to-head evidence comparison — which supplement is right for you?
Vitamin C wins 2 of 3 categories. Both are solid choices — the best pick depends on your specific goals.
Verdict
Likely helps
12 of 17 studies with measurable effects showed benefit.
Top outcomes
Verdict
Likely helps
12 of 15 studies with measurable effects showed benefit.
Top outcomes
Shared outcomes (1)
Outcomes where both Vitamin C and Vitamin K2 have evidence — compare verdict strength side-by-side.
500-1000mg
With meals, Split doses if taking >500mg
Ascorbic acid or buffered vitamin C
100-200mcg (MK-7)
With a meal containing fat
MK-7 (menaquinone-7)
Ongoing
1-2 weeks
4-8 weeks
With high doses (>2g)
6-12 months
1-3 years
Vitamin C supplementation for prevention and treatment of pneumonia
The Cochrane database of systematic reviews (2020) · Meta analysis · n=2774
We are uncertain of the effect of vitamin C supplementation on mortality due to pneumonia (RR 0.21, 95% CI 0.03 to 1.66; 1 study, 57 participants; very low-quality evidence).
Vitamin C supplementation in pregnancy
The Cochrane database of systematic reviews (2015) · Meta analysis · n=20038
Conversely, the risk of term PROM was increased when supplementation included vitamin C and vitamin E (average RR 1.73, 95% CI 1.34 to 2.23; 3060 participants; two studies; I² = 0%).
Enhanced Vitamin C Delivery: A Systematic Literature Review Assessing the Efficacy and Safety of Alternative Supplement Forms in Healthy Adults
Nutrients (2025) · Systematic review
Most studies (77%) had a low risk of bias.
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.
Based on 3 meta-analyses of sepsis patients. One study showed RR 0.60 for mortality reduction, but another showed increased risk (RR 1.21). Evidence quality rated as low to very low. Effect limited to intravenous administration in critically ill patients.
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 C has a higher evidence score (8/10 vs 6/10) and wins in 2 of 3 categories.
For bone health, Vitamin K2 has a higher relevance score (88 vs 70).
No known interactions between Vitamin C and Vitamin K2 have been documented in our database. However, always consult a healthcare provider before combining supplements.