What is vitamin K?
Vitamin K is a family of compounds, most famously known for their role in blood clotting. However, their physiological functions differ quite dramatically as the compounds within the family vary from each other.
What are the claimed benefits?
What the science says
Spoiler alert! - more research is needed. Here’s what we do know:
Two main classifications of vitamin K are K1 and K2. K1 comes primarily from plants we eat, while K2 is produced by healthy gut bacteria and absorbed into the bloodstream through the intestinal wall. Bacteroides and Prevotella are two of the genus, or family, of gut bacteria that produce vitamin K2, with bacteroides being more prevalent in healthy human gastrointestinal tracts.
Research is currently mixed on the benefits of supplementation with various subtypes of both vitamin K1 and K2 for prevention and treatment for low bone density although we know that people with vitamin K deficiency have higher risk for low bone density - osteoporosis. Two K2 subtypes, MK-4 and MK-7, show potential benefit in reducing bone loss and fracture risk, although, interestingly, they do not always yield an increase in bone mineral density. This points to the notion in more recent decades that bone matrix modeling may be a stronger determinant of true fracture risk than the density itself. Still, more research is needed to understand vitamin K’s role in bone health.
There is more consistent research for vitamin K1/K2 and reducing risk of calcium deposits and hardening of arteries, leading to cardiovascular disease. However, this evidence was most strongly shown with dietary intakes of vitamin K, and was not reproduced when supplement forms were taken.
The Apeiron Life perspective
Vitamin K status is notoriously difficult to assess in humans as blood values vary dramatically and the clinical significance of these variations is not well understood. Most often, people on anticoagulants have their prothrombin time measured to gauge how quickly their blood clots. This is used as a proxy for vitamin K status, although this too has its flaws.
We recommend eating a balanced Mediterranean Diet, which naturally includes foods that are both rich in vitamin K1 and K2 as well as foods that are high in fiber that feed your gut bacteria that then produce vitamin K2 for you - thank you microbes!
Vitamin K1 - think greens!
A few more foods to feed you and your hard-working, K2 producing microbes:
Vegetables: onions, garlic, leeks, shallots, spring onion, asparagus, dandelion greens, jerusalem artichokes (sunchokes), chicory, beets, fennel, green peas, snow peas, sweetcorn, savoy cabbage, eggplant, endive, radicchio, jicama root
Fruits: nectarines, peaches, persimmon, tamarillo, watermelon, rambutan, grapefruit, pomegranate, dried dates and figs, apples, bananas
Grains: barley, rye bread & crackers, whole wheat pasta & bread, wheat bran, oats
Legumes: chickpeas, lentils, red kidney beans, black beans, soybeans
Nuts & seeds: cashews, pistachios, flax
Will a supplement benefit you?
Likely not. With mixed research on any real benefits of vitamin K supplements, along with some research showing potential for harm with increased risk for uncontrolled bleeding - we recommend you sit this one out and stick with K-rich foods.
Still curious to try a supplement?
Just don't. But if you do, discuss with your doctor any possible adverse medication interactions and notice if you find yourself bruising or bleeding more easily. Stop the supplement immediately and contact your doctor if you do.