Vitamin K2 is often marketed as a supplement for “bones and arteries”. The evidence is less simple: K1 and K2 belong to the same family, studied forms do not all produce the same results, and warfarin changes the safety question completely.
1. K1, K2, MK-4 and MK-7 Vitamin K includes phylloquinone (K1) and menaquinones (K2), including the studied forms MK-4 and MK-7. K1 is found mainly in leafy green vegetables. Menaquinones occur in varying amounts in some fermented and animal foods. A label saying “K2” therefore does not, by itself, describe the form, dose or expected effect.
2. What bone studies actually show In postmenopausal women, a meta-analysis of 16 randomized trials (6,425 participants) found a signal for improved lumbar bone mineral density, while the overall analysis showed no significant difference in fractures.
3. Is the “artery protection” claim established? Vitamin K-dependent proteins are involved in mechanisms studied in bone and blood vessels. That explains scientific interest, not clinical proof. Current data do not show that a K2 supplement alone prevents cardiovascular disease.
4. Should you take a supplement? EFSA set an adequate intake for phylloquinone, not a specific adult recommended intake for K2. Start by considering diet and context: restrictive diets, malabsorption, bariatric surgery or certain medicines may justify professional advice.
5. The interaction not to miss Vitamin K has an important interaction with warfarin and related vitamin K antagonists: intake should remain consistent and supplementation should be discussed with a professional. Do not start, stop or change a K2 supplement without telling your doctor or pharmacist.
06FAQ ### Is K2 the same as K1? They belong to the vitamin K family, but K1 and K2 cover different molecules and food sources. MK-4 and MK-7 are two studied menaquinones.
01Is K2 required with vitamin D? The sources reviewed do not support presenting this combination as a general rule. Supplementation should match an identified need and account for medicines.
02What dose should you choose? There is no universal dose to recommend here. Studies use different forms and protocols; a product label is not a personal prescription.
Sources The references are listed in the article evidence file.
Sources
Peer-reviewed studies and institutional references used for this article.
- 1Ma et al., Frontiers in Public Health· 2022LimitedView source
- 2NIH Office of Dietary Supplements· 2021EstablishedView source
- 3NIH Office of Dietary Supplements· 2021EstablishedView source
- 4EFSA· 2017EstablishedView source
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By
Claire Mercier
Registered nutritionist focused on whole-food diets and metabolic health.
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