Calcium and Vitamin K2: The Relationship Most People Get Wrong

Calcium supplementation for bone health has been widely recommended for post-menopausal women for decades. The evidence that it reduces fracture risk is, on its own, weaker than commonly assumed. A 2010 meta-analysis published in the BMJ found that calcium supplementation alone, without co-supplementation with Vitamin D, did not significantly reduce fracture rates and was associated with a 27 to 31 percent increase in cardiovascular events in some cohorts. The explanation lies in the role of Vitamin K2 in calcium metabolism.

What Vitamin K2 Does

Vitamin K2 activates two proteins that govern where calcium is deposited in the body. Matrix Gla-protein, activated by K2, inhibits calcium deposition in arterial walls. Osteocalcin, also activated by K2, promotes calcium deposition in bone matrix. Without adequate K2, supplemental calcium circulates in the blood without clear directional signals and is more likely to deposit in soft tissues including arterial walls. With adequate K2, calcium is directed preferentially into bone.

The Rotterdam Study

The Rotterdam Study, one of the largest long-term cardiovascular cohort studies, found that high dietary Vitamin K2 intake was associated with a 52 percent reduction in aortic calcification and a 57 percent reduction in cardiovascular mortality over 7 to 10 years of follow-up. Vitamin K1, the form found in leafy greens, did not produce the same cardiovascular benefit, suggesting that the MK-7 form of K2 found in fermented foods and cheese is the clinically relevant variant.

Sources

• 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.
• Bolland, M.J., et al. (2010). Effect of calcium supplements on risk of myocardial infarction and cardiovascular events: meta-analysis. BMJ, 341, c3691.
• Knapen, M.H.J., et al. (2013). Three-year low-dose menaquinone-7 supplementation helps decrease bone loss in healthy postmenopausal women. Osteoporosis International, 24(9), 2499-2507.