Comparison
Omega-3 (EPA/DHA) vs Vitamin D3 + K2
Side-by-side of Omega-3 (EPA/DHA) and Vitamin D3 + K2. Every row below is pulled from the compound schema and will update as our data grows. For deeper reads, follow through to each compound page.
Omega-3 (EPA/DHA)
Omega 3 fish oil profile: EPA/DHA marine fatty acids, 2-4 g/day cuts triglycerides 20-30%, REDUCE-IT showed 25% cardiovascular risk reduction on icosapent eth.
Vitamin D3 + K2
Vitamin D3 K2 supplement profile: cholecalciferol at 1000-4000 IU/day corrects deficiency, MK-7 directs calcium to bone, away from arteries.
Effects at a glance
Omega-3 (EPA/DHA)
- •Reduces fasting triglycerides 20-50% at 2-4 g/day in hypertriglyceridemic patients
- •REDUCE-IT showed 25% relative risk reduction in major CV events at 4 g/day icosapent ethyl
- •Modest antidepressant effect (SMD ~0.40) for EPA-dominant formulations at 1-2 g/day
- •Atrial fibrillation incidence rises ~30-50% at 4 g/day; relevant for older patients with pre-existing CV disease
- •Tissue omega-3 index (RBC EPA + DHA) target ~8%; Western baseline typically 4-5%
- •Triglyceride and re-esterified triglyceride forms absorb ~70% better than ethyl esters in fasted state
Vitamin D3 + K2
- •Reduces non-vertebral fractures 10-20% in older adults at 800 IU/day or above when combined with calcium
- •VITAL trial showed neutral results on primary CV and cancer endpoints at 2000 IU/day over 5 years
- •Vitamin D supplementation reduces respiratory infection incidence ~10-20% in deficient populations
- •K2 MK-7 has 72-hour plasma half-life vs 1-2 hours for MK-4; once-daily dosing is sufficient
- •Synergy hypothesis is largely preclinical; dedicated combination RCTs are limited
- •Daily dosing outperforms bolus dosing for immune and infection outcomes
Side-by-side
| Attribute | Omega-3 (EPA/DHA) | Vitamin D3 + K2 |
|---|---|---|
| Category | supplement | supplement |
| Also known as | fish oil, EPA, DHA, marine omega-3 | cholecalciferol + menaquinone, D3/K2, vitamin D3 with MK-7 |
| Half-life (hr) ↗ | 48 | 360 |
| Typical dose (mg) ↗ | 2000 | 0.05 |
| Dosing frequency | 1 to 2 times daily with food | daily with a fat-containing meal |
| Routes | oral | oral |
| Onset (hr) | 4 | 24 |
| Peak (hr) | 12 | 168 |
| Molecular weight | 302.45 | 384.64 |
| Molecular formula | C20H30O2 (EPA); C22H32O2 (DHA) | C27H44O (D3); C46H64O2 (MK-7) |
| Mechanism | Substitutes arachidonic acid in membrane phospholipids, shifting eicosanoid production toward less-inflammatory 3-series prostaglandins and 5-series leukotrienes. Activates PPAR-alpha to lower hepatic VLDL/triglyceride synthesis. DHA modulates synaptic membrane fluidity and neuronal function. | D3 converts to calcidiol then calcitriol, activating the vitamin D receptor (VDR) to increase intestinal calcium absorption and modulate immune and bone gene transcription. K2 carboxylates osteocalcin and matrix Gla protein, directing calcium toward bone and inhibiting vascular calcification. |
| Legal status | Dietary supplement; prescription forms (icosapent ethyl, omega-3 acid ethyl esters) for severe hypertriglyceridemia | Dietary supplement (global) |
| WADA status | allowed | allowed |
| DEA / Rx | Not scheduled | Not scheduled |
| Pregnancy | Recommended at 200 to 600 mg DHA/day for fetal development | Recommended at standard doses for fetal bone development; consult clinician at higher doses |
| CAS | 10417-94-4 | 67-97-0 |
| PubChem CID | 446284 | 5280795 |
| Wikidata | Q207688 | Q139347 |
Safety profile
Omega-3 (EPA/DHA)
Common side effects
- fishy aftertaste
- eructation (fish burps)
- mild dyspepsia
- loose stools at high doses
Contraindications
- fish allergy (use algal omega-3 alternative)
- active bleeding disorders
- scheduled surgery (discontinue 5-7 days prior)
Interactions
- warfarin and DOACs: additive antiplatelet effect at 2+ g/day; meaningful bleeding risk(moderate)
- aspirin and antiplatelet agents: additive bleeding risk at high doses(moderate)
- statins: complementary cardiovascular effects; no pharmacokinetic interaction(minor)
- antiarrhythmics: high-dose omega-3 increases AF risk; relevant in pre-existing arrhythmia(moderate)
Vitamin D3 + K2
Common side effects
- GI upset at high doses
- headache (rare)
- hypercalcemia (only at sustained very high D3 doses)
Contraindications
- hypercalcemia
- sarcoidosis
- active hyperparathyroidism
- warfarin therapy (K2 component requires stable intake)
Interactions
- warfarin: K2 component can affect anticoagulation; maintain stable intake and inform anticoagulation clinic(moderate)
- thiazide diuretics: additive calcium retention; hypercalcemia risk with high-dose D3(moderate)
- digoxin and calcium channel blockers: additive effects from D3-induced hypercalcemia(moderate)
- glucocorticoids: reduced vitamin D efficacy and bone effects(moderate)
- cholestyramine and orlistat: bind fat-soluble vitamins; separate dosing by 2 to 4 hours(moderate)
Which Should You Take?
Omega-3 (EPA/DHA) and Vitamin D3 + K2 score evenly on the criteria we weight (goal breadth, legal accessibility, evidence depth). The conditionals below should drive the decision more than any aggregate score.
- → If your priority is focus or working memory, pick Omega-3 (EPA/DHA).
- → If your priority is bone density, pick Vitamin D3 + K2.
- → If your priority is cardiovascular health, pick Omega-3 (EPA/DHA).
Edge case: Half-lives differ materially (Omega-3 (EPA/DHA) ~48 hr vs Vitamin D3 + K2 ~360 hr). Vitamin D3 + K2 reaches steady state faster; Omega-3 (EPA/DHA) is easier to dial in if tolerability is uncertain.
Default choice: either is defensible. Omega-3 (EPA/DHA) edges out on goal breadth + legal accessibility; Vitamin D3 + K2 is the right call if your priority sits in the goals listed above.
This verdict is generated from each compound's schema (goals, legal status, evidence outcomes, dosing route). It updates automatically as our compound data evolves; the deeper read sits on each individual compound page.
Common questions
What is the difference between Omega-3 (EPA/DHA) and Vitamin D3 + K2?
Omega-3 (EPA/DHA) and Vitamin D3 + K2 differ in category (supplement vs supplement), mechanism, and typical dosing. See the side-by-side table for full details.
Which has a longer half-life, Omega-3 (EPA/DHA) or Vitamin D3 + K2?
Omega-3 (EPA/DHA) half-life is 48 hours; Vitamin D3 + K2 half-life is 360 hours.
Can you stack Omega-3 (EPA/DHA) with Vitamin D3 + K2?
Stack compatibility depends on mechanism overlap, legal status, and individual response. Check each compound page for specific interactions and contraindications before combining.
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