Menaquinone (vitamin K2)

EFSA 2009 approved the claim “vitamin K contributes to bone health maintenance” for labelling. Evidence on oral K2 in postmenopausal osteoporosis is limited: the 2008 Booth RCT did not show a significant effect on bone mineral density or fractures. Endocrine Society 2019 does not include K2 in osteoporosis treatment standards. Standard therapy: bisphosphonates, denosumab, teriparatide + calcium + vitamin D.

Japanese guidelines for postmenopausal osteoporosis include MK-4 at 45 mg daily, but this is a narrow local practice not supported by international consensus.

Vitamin K2 (menaquinone) is a fat-soluble vitamin found in fermented foods (natto, aged cheeses). Its clinical indication is vitamin K deficiency prevention (rare). In anti-aging communities, vitamin K2 is sold to slow aging, protect against vascular calcification, and support bone health, often combined with vitamin D3. Clinical studies of prophylactic K2 use in healthy adults are small and heterogeneous; international anti-aging and CV-prevention guidelines do not include vitamin K2. K2 intake is dangerous in people on warfarin or other vitamin K antagonists – it sharply reduces their effect with thrombosis risk. If vitamin K2 is being taken for anti-aging, consider seeking a second opinion, especially if you take anticoagulants.

Cochrane 2020 found no evidence for vitamin K (including K2) in primary cardiovascular prevention. The 2021 JAHA RCT in patients with coronary calcification showed some slowing of progression – not reproduced in larger RCTs. ESC, AHA do not include K2 in cardiology recommendations. The marketing position “K2 prevents vascular calcification” outpaces the evidence.