Nutrition Diet: What is the Best Form of K2 for Optimal Health?

October 13, 2025 •

3 min read

While many are familiar with vitamin K's role in blood clotting, fewer know its critical function in directing calcium to the right places. Vitamin K2, specifically its MK-4 and MK-7 forms, is central to this process, leading to the key question: what is the best form of K2 for overall wellness?

Quick Summary

This article provides a comparison of the MK-4 and MK-7 forms of vitamin K2, explaining their distinct sources, bioavailability, and half-life. It examines the evidence for their respective roles in supporting bone and heart health and offers guidance on supplementation.

Key Points

MK-7 is superior for supplementation: Due to its longer half-life and better bioavailability, MK-7 is generally the preferred form for supplements, effective in lower, once-daily doses.
MK-4 is rapidly cleared: MK-4 has a very short half-life and is poorly absorbed at nutritional doses, making it less effective for supplementation than MK-7.
MK-7 supports heart health: Evidence shows MK-7 is effective at activating Matrix Gla Protein (MGP), which prevents arterial calcification and supports cardiovascular health.
MK-4 has higher dose applications: While less bioavailable at nutritional levels, high-dose MK-4 (45mg) is used therapeutically in Japan to treat osteoporosis, with studies showing a reduction in fractures.
Source differences matter: MK-7 is primarily found in fermented foods like natto, while MK-4 is in animal products such as egg yolks and liver, but in smaller amounts.
Take with fat: As a fat-soluble vitamin, both forms of K2 are best absorbed when consumed with dietary fat.
Consider medication interactions: Individuals on blood-thinning medication like warfarin should consult a doctor before starting K2 supplements due to potential interactions.

Vitamin K is a fat-soluble vitamin crucial for activating proteins involved in blood clotting and calcium metabolism. It has two main natural forms: vitamin K1 (phylloquinone) in leafy greens and vitamin K2 (menaquinones) in animal and fermented foods. The most studied K2 subtypes, menaquinone-4 (MK-4) and menaquinone-7 (MK-7), have key differences affecting their efficacy.

The Role of Vitamin K2 in the Body

Vitamin K2 activates vitamin K-dependent proteins (VKDPs) through carboxylation. These proteins include:

Osteocalcin: Helps integrate calcium into bone, promoting strength.
Matrix Gla Protein (MGP): Prevents calcium deposition in soft tissues like arteries.

Insufficient K2 can lead to calcium being directed away from bones and into arteries, potentially contributing to osteoporosis and cardiovascular disease.

Vitamin K2: The Tale of Two Menaquinones (MK-4 and MK-7)

MK-4 and MK-7 both activate VKDPs, but their distinct structures, metabolism, and bioavailability result in different effects.

Menaquinone-4 (MK-4)

MK-4 is a short-chain menaquinone in some animal products and is synthesized from K1 in tissues. Key points about MK-4:

Short Half-Life: Cleared rapidly from the bloodstream, requiring frequent, high doses for consistent levels.
High Dosage: Therapeutic doses used for osteoporosis in Japanese studies (45 mg) are significantly higher than typical supplement amounts.
Nutritional Bioavailability: At standard supplement doses, MK-4 is not well-absorbed and doesn't significantly raise serum levels.

Menaquinone-7 (MK-7)

MK-7 is a long-chain menaquinone from fermented foods like natto. It is better suited for supplementation due to:

Long Half-Life: Stays in the bloodstream for about 72 hours, distributing to tissues. This allows for once-daily dosing.
High Bioavailability: Well-absorbed and accumulates in the body, providing a stable supply for activating VKDPs.
Effectiveness at Lower Doses: Effective at lower nutritional doses than MK-4 due to better bioavailability and half-life.

MK-4 vs. MK-7 Comparison Table


Feature	MK-4 (Menaquinone-4)	MK-7 (Menaquinone-7)
Primary Source	Animal products (egg yolks, liver, meat); synthesized in tissues from K1	Fermented foods (especially natto), some cheeses
Half-Life	Short (approx. 2-6 hours)	Long (approx. 72 hours)
Bioavailability	Poor at nutritional doses; cleared rapidly	High; well-absorbed and accumulates over time
Dosage for Effect	High therapeutic doses required (e.g., 45 mg)	Low nutritional doses effective (e.g., 90-180 mcg)
Dosing Frequency	Multiple times per day for consistent effect	Once daily is sufficient
Focus of Research	Historically used in Japan for osteoporosis; synthetic forms available	Widely researched for bone and cardiovascular health
Research Outcome	Studies show benefits for fracture risk, but evidence on BMD is mixed and often relies on high doses.	Several studies show positive effects on bone mineral density and arterial stiffness.

The Best Form of K2 for Health Outcomes

For general supplementation, MK-7 is widely considered superior due to its high bioavailability and long half-life. This ensures consistent activation of VKDPs supporting bone and cardiovascular health. While high-dose MK-4 has shown benefits, its rapid clearance and poor bioavailability at nutritional levels make it less reliable for supplementation.

Bone Health

MK-7's prolonged availability allows for more effective and consistent activation of osteocalcin at lower doses. Studies on MK-7 have shown benefits for bone mineral density, particularly in postmenopausal women, though some studies have had mixed results. High-dose MK-4 studies, mainly from Japan, have shown a reduction in fracture risk.

Cardiovascular Health

MK-7 is particularly beneficial for heart health as it effectively activates MGP, preventing arterial calcification. The Rotterdam Heart Study linked high dietary menaquinone intake (including MK-7) to a reduced risk of coronary heart disease and aortic calcification, unlike K1. MK-7's long half-life helps it consistently target calcium buildup in arteries.

How to Supplement with K2

When choosing a supplement, MK-7 is often recommended for its high bioavailability and long half-life, allowing for once-daily dosing. Since it's a fat-soluble vitamin, take K2 with a meal containing fat for optimal absorption. Consult a healthcare provider before supplementing, especially if taking blood thinners like warfarin, as vitamin K can interfere with these medications.

Conclusion: Making the Right Choice

While both MK-4 and MK-7 offer health benefits, MK-7 is generally preferred for supplementation due to its superior bioavailability, long half-life, and effectiveness at lower daily doses. Its sustained presence in the bloodstream ensures consistent activation of proteins essential for bone and heart health. Dietary sources of MK-7 are primarily natto, while MK-4 is found in smaller amounts in animal products. Given the difficulty of obtaining therapeutic levels from food alone, supplementation is often considered. For most consumers and practitioners, MK-7 is the more practical and effective option.

For more in-depth information, the National Institutes of Health offers detailed fact sheets on vitamin K for health professionals.

Frequently Asked Questions

MK-4 has a short half-life and is poorly absorbed at nutritional doses, while MK-7 has a long half-life of about 72 hours, is highly bioavailable, and can be taken once daily.

MK-7 is generally considered superior for bone health supplementation due to its longer half-life and consistent activation of bone-building proteins at lower doses. High-dose MK-4 has shown benefits in Japanese studies, but is not practical to get from food or typical supplements.

MK-7 is particularly effective for cardiovascular health. Its long half-life ensures continuous activation of Matrix Gla Protein (MGP), which helps prevent calcium from depositing in arterial walls.

The richest food source of MK-7 is natto, a Japanese fermented soybean dish. Other fermented foods like some aged cheeses (Gouda, Brie) contain moderate amounts.

MK-4 is found in animal products, including grass-fed butter, egg yolks, and organ meats like chicken or goose liver. However, the amounts are often insufficient to provide a therapeutic effect from diet alone.

Vitamin K is a fat-soluble vitamin. Consuming it with a meal that contains healthy fats, such as olive oil, avocado, or the natural fats in K2-rich foods, significantly enhances its absorption by the body.

If you are taking blood-thinning medications like warfarin, you should not take a vitamin K2 supplement without strict medical supervision. Consistent vitamin K intake is critical to managing the medication, and supplements can interfere with this balance.