Christopher Labos: Vitamin K2's social-media hype is overblown

Article content

Vitamin fads come and go. Once, everyone took vitamin D until the clinical trials showed it didn’t really live up to the hype. Now, vitamin K2 is popping up in social media circles with the promise that it will treat both heart disease and osteoporosis. But like its predecessors, the scientific data doesn’t match the social media claims.  

To begin, we have to distinguish between the different K vitamins. Vitamin K1 (phylloquinone) is found mostly in plants, particularly green vegetables like spinach and broccoli. Vitamin K2 (menaquinone) is the form found in animals. However, animal products are a negligible source of vitamin K in our diet; almost all the vitamin K we consume is phylloquinone from plant sources. But the distinction is academic. Vitamin K1 is converted into vitamin K2 in our bodies, in part by bacteria in our intestines. 

Article content

Vitamin K’s main biological role is the activation of several blood coagulation factors. You need vitamin K for your blood to clot properly, and without it you would have severe hemorrhages. Medically, it was used to reverse the effects of a blood thinner like Coumadin, though Coumadin is used less frequently than it once was. There is one other situation in which vitamin K is used routinely: Infants are uniformly vitamin K deficient and need a single dose at birth to prevent bleeding. 

For adults, vitamin K deficiency is quite rare and would occur only if they had liver failure or some disease that prevented its absorption from the intestine, like Crohn’s disease. 

Given its central role in bleeding and coagulation, one may wonder why we are discussing it in the context of osteoporosis. But vitamin K also activates proteins like osteocalcin that have a role in bone mineralization, and this has led some people to champion its use as an osteoporosis treatment.  

There are several problems with this theory. Firstly, very few people are actually vitamin K deficient, and taking more of a vitamin doesn’t make it work better once you have the necessary amount in your system. Second, researchers have tested the impact of vitamin K on bone density and found no significant benefit in most of the studied populations. Some review articles have tried to spin the benefits and cherry-pick the results. They trumpeted the increase in bone mineral density of the spine, but failed to highlight that bone density in the hip was unchanged. There was also no reduction in fracture risk. For those worried about osteoporotic fractures, much better therapies exist. 

Article content

Whereas vitamin K promotes the calcification (and therefore strengthening) of bones, it seems to prevent the calcification of arteries. Because coronary calcifications are a predictor of heart disease risk, inhibiting arterial calcification should theoretically be beneficial. But most people misunderstand what coronary calcifications mean. They are a marker of high risk factor burden and are driven by age (which we cannot control) and traditional risk factors like smoking, diabetes, high blood pressure and cholesterol (which we can). Even if we could inhibit the calcification of arteries, I’m not convinced it would accomplish much if we didn’t address the underlying reasons those arteries were being calcified in the first place.

Even so, the studies to date have not been encouraging and most show that vitamin K2 had little effect on vascular calcifications. More importantly, though, the underlying core of cardiology care is the use of blood thinners to prevent coronary disease. Vitamin K, even if it did significantly prevent vascular calcifications, would still be pro-coagulant in its activity. This fundamental discrepancy makes me skeptical the research will bear out any benefit. 

Vitamin K, in whatever variety you take it, has one clear medical purpose: It prevents major hemorrhage and can reverse severe bleeding if you are an infant with no vitamin K in your system or an adult taking too high a dose of Coumadin. It doesn’t delay osteoporosis or coronary calcifications to any meaningful degree. Come find me when the next vitamin fad hits. 

Christopher Labos is a Montreal physician, co-host of the Body of Evidence podcast and author of Does Coffee Cause Cancer?

Article content

Article content