Vitamin K2 (menaquinone): benefits, role, food sources and precautions

Vitamin K2 was long overlooked and treated as equivalent to vitamin K1, the clearest evidence being that there is still no official recommendation for its daily intake!

Today, vitamin K2 (or menaquinone) is attracting growing scientific interest for its specific benefits. Both forms of vitamin K are fat-soluble, which is their main shared characteristic, but their functions, food sources and bioavailability differ considerably.

Vitamin K2 plays a fundamental role in calcium metabolism, with a significant impact on bone and cardiovascular health.

In this article, we review the current scientific evidence on vitamin K2, its mechanisms of action and, in particular, the MK-7 form, recognized as the most bioavailable and active form in the human body.

The role of vitamin K2 in the body

Vitamin K2 plays a fundamental role in calcium metabolism and complements the action of vitamin D. It helps direct calcium toward the bones rather than the arteries. As such, it is essential for bone and cardiovascular health.

1. Vitamin K2 and bone health

Osteoporosis affects millions of people worldwide, and vitamin K2 is a key but often overlooked factor in its prevention.

Clinical trials show that vitamin K2 supplementation significantly increases bone mineral density and reduces the risk of vertebral fractures.

A meta-analysis published in Osteoporosis International (Fang et al., 2012), which included 19 randomized studies, concluded that vitamin K2 reduced the risk of vertebral fractures by 60%, hip fractures by 77% and non-vertebral fractures by 81% in Japanese postmenopausal women.

These findings are consistent with the action of vitamin K2 on calcium deposition in bones.

2. Cardiovascular health: the importance of vitamin K2

Limiting calcium deposits in the arteries is essential for maintaining cardiovascular health.

When calcium accumulates in blood vessel walls, they gradually lose their elasticity, their diameter narrows and blood pressure may increase.

Vitamin K2 helps prevent this process by activating Matrix Gla Protein (MGP), one of the most powerful known inhibitors of vascular calcification.

Once activated, MGP prevents calcium from being deposited in the arteries and directs it toward its natural destination: bone tissue.

Vitamin K2 therefore works alongside vitamin D, which promotes calcium absorption but does not control how calcium is distributed throughout the body.

This action is supported by the Rotterdam Study [2], conducted among more than 4,800 people followed for 10 years.

Vitamin K2: what are the interactions and precautions?

Vitamin K2 is contraindicated in people taking vitamin K antagonist anticoagulants, such as warfarin, because it can alter their effectiveness.
Any supplementation should therefore be discussed with the prescribing physician.

Outside this specific situation, vitamin K2 has an excellent safety profile. Unlike excessive vitamin D3 intake, it does not increase calcium levels in the blood (hypercalcemia), but instead contributes to a better distribution of calcium throughout the body.

Which foods are highest in vitamin K2?

Vitamin K2 is much less common in Western diets than vitamin K1.

It is mainly produced through bacterial fermentation, which explains why fermented foods are its best sources and why Western diets, which tend to contain few fermented foods, are more likely to provide insufficient amounts.

It is also important to distinguish between the molecular forms found in different foods:

• Animal products mainly provide MK-4 (a short half-life form, meaning it remains in the bloodstream for a shorter period and is therefore less effective).
  
  

• Fermented foods provide MK-7 (a longer-lasting and more bioavailable form).

What are the daily requirements for vitamin K2?

Vitamin K2 requirements are estimated at between 90 and 180 µg per day, depending on the populations studied and the goals related to bone and cardiovascular health.

However, reaching these intake levels through diet alone can be difficult.

In practice, natto, a traditional Japanese food made from fermented soybeans, is one of the very few naturally rich sources of vitamin K2 (MK-7).

As it is rarely consumed in Europe, dietary intake is often insufficient.

This is why vitamin K2 (MK-7) supplementation may be a relevant option, particularly when combined with vitamin D3, to support the proper use of calcium by the body.

Vitamin K2 vs K1: what are the differences and their roles?

Vitamin K1 (phylloquinone): primarily for blood clotting

Vitamin K1 primarily helps support normal blood clotting. It activates several proteins in the liver that are essential for blood clot formation, including certain coagulation factors. Without sufficient vitamin K1 intake, the body is less able to clot blood effectively, which can increase the risk of bleeding.

Also known as phylloquinone, vitamin K1 is mainly derived from plant sources. It is found primarily in green leafy vegetables such as spinach, kale, Swiss chard and broccoli.

Vitamin K2 (menaquinone): essential for the proper use of calcium

Vitamin K2 refers to a family of molecules known as menaquinones, with variants ranging from MK-4 to MK-13.

It primarily plays a role in calcium metabolism and helps direct calcium toward the bones.

Vitamin K2 is an essential cofactor for the activation of Gla proteins, two of which play a crucial role:

• Osteocalcin (OC): a protein synthesized by bone cells (osteoblasts), it cannot bind calcium to bone without vitamin K2.

• Matrix Gla Protein (MGP): a protein that inhibits vascular calcification, it is activated by vitamin K2 to help prevent calcium deposits in arterial walls.

Conclusion

Vitamin K2 is a micronutrient with significant benefits that was overlooked for far too long. By directing calcium toward the bones while helping prevent its deposition in the arteries, it plays a fundamental role that complements vitamin D, an effect that is now well documented scientifically.

Western diets, which tend to be low in fermented foods, can result in insufficient intake for a large proportion of the population. Targeted vitamin K2 supplementation, particularly in the MK-7 form, may therefore be worth considering, especially for postmenopausal women and as part of an approach to supporting cardiovascular and bone health in adults.

Vitamin K2 MK-7 is included in several Argalys formulas (Multivitamins, MultiKid, Calcium, D3 and Vitamin K2), where it is combined with appropriate cofactors for optimal effectiveness.

Scientific references

1. Vermeer C. et al. (2004). Beyond deficiency: potential benefits of increased intakes of vitamin K for bone and vascular health. European Journal of Nutrition, 43(6), 325–335.

2. Geleijnse J.M. et al. (2004). Dietary intake of menaquinone is associated with a reduced risk of coronary heart disease: the Rotterdam Study. Journal of Nutrition, 134(11), 3100–3105.

3. Schurgers L.J. et al. (2007). Vitamin K-containing dietary supplements: comparison of synthetic vitamin K1 and natto-derived menaquinone-7. Blood, 109(8), 3279–3283.

4. Fang Y. et al. (2012). Effect of vitamin K on bone mineral density: a meta-analysis of randomized controlled trials. Journal of Bone and Mineral Research, 27(9), 1932–1942.

5. Knapen M.H. et al. (2013). Three-year low-dose menaquinone-7 supplementation helps decrease bone loss in healthy postmenopausal women. Osteoporosis International, 24(9), 2499–2507.

6. Szulc P. et al. (1996). Serum undercarboxylated osteocalcin is a marker of the risk of hip fracture in elderly women. Journal of Clinical Investigation, 91(4), 1769–1774.

7. EFSA Panel on Dietetic Products (2017). Safety of menaquinone-7 as a novel food pursuant to Regulation (EC) No 258/97. EFSA Journal, 15(5).