Landmark Clinical Evidence
Hard endpoint trials and systematic reviews — not surrogate markers alone
| Trial / Study | N | Dose | Duration | Key Finding |
|---|---|---|---|---|
| VITAL Trial (NEJM 2019) | 25,871 | 2,000 IU D3 + 1g omega-3 | 5.3 years | −25% cancer mortality (years 2–5); −28% MI risk in non-fish eaters |
| D-HEALTH (Lancet Diabetes, 2022) | 311 | 60,000 IU/month bolus | 3 years | Improved insulin sensitivity; −25% HbA1c vs. placebo in pre-diabetics |
| ViDA (JAMA 2022) | 5,108 | 100,000 IU/month | 3.3 years | Reduced acute respiratory infections; −20% severe ARI requiring hospitalization |
| Bassatne et al. Meta-analysis (2021) | 43,000+ | Varies | Various | −15% all-cause mortality in those with baseline deficiency (25-OH-D <20 ng/mL) |
| Rotterdam Study (2004) | 4,807 | Dietary K2 (MK-4/7) | 7.2 years | Highest K2 intake → −41% CHD mortality; −57% aortic calcification; −26% all-cause mortality |
| EPIC-Heidelberg (2010) | 24,340 | Dietary MK intake | 10 years | Each 10mcg/day MK increase → −9% CHD events |
D3 upregulates calcium absorption from the gut and Osteocalcin expression. Without K2 (MK-7), that calcium can deposit in arteries rather than bone — increasing cardiovascular risk. K2 activates Matrix Gla Protein (MGP), which actively inhibits arterial calcification.
VDR is expressed in virtually every cell type including immune cells, cardiomyocytes, brain neurons, and pancreatic beta cells. D3 acts as a transcription factor regulating over 200 genes — including those controlling inflammation, cell differentiation, and apoptosis.
Large observational studies link severe COVID-19 outcomes to D3 deficiency. The Castillo et al. RCT (Spain, 2020) found calcifediol supplementation reduced ICU admission by 96% in hospitalized patients — though this used the activated form and results warrant replication.
Target serum 25(OH)D levels of 50–80 ng/mL for longevity optimization (vs. the conventional "sufficient" cutoff of 30 ng/mL). Regular testing guides dosing — over-supplementation above 150 ng/mL causes hypercalcemia. Test every 6 months when supplementing.
Dosing Protocol
Dose to serum level, not to a fixed number — individual variation is very high
Evidence-Based Dosing (D3 + K2)
⚠ Safety Considerations
D3 toxicity requires sustained intake above 10,000 IU/day for months — rare at recommended doses. K2 (MK-7) is extremely safe; may interact with Vitamin K antagonist anticoagulants (warfarin) — monitor INR if prescribed. Magnesium is required for Vitamin D conversion to its active form — ensure adequate Mg intake alongside D3.
Best Products by Evidence
Evaluated for D3 form (cholecalciferol preferred), K2 form (MK-7 preferred), and bioavailability data
Liquid form allows precise dose titration. Ideal for optimizing to serum levels. MCT oil carrier improves absorption. Thorne's NSF certification is the gold standard for supplement purity.
Get on Fullscript ↗Best combination of MK-7 dosing and value. Includes K1 for additional clotting factor support. High D3 dose (5,000 IU) appropriate for deficient individuals — retest serum levels.
Get on Fullscript ↗Excellent entry-level option for maintenance supplementation. Low individual dose makes it easy to titrate. NOW Foods maintains consistently clean manufacturing — solid value choice.
Get on Fullscript ↗