Most people have heard of vitamin D. Many know about vitamin C. But vitamin K2 tends to get much less attention.
That doesn’t mean it’s unimportant.
Vitamin K is a fat-soluble vitamin involved in several important processes in the body, including normal blood clotting and bone metabolism. Vitamin K2 is a group of forms known as menaquinones, including MK-4 and MK-7.
So what are the benefits of vitamin K2, where can you get it, and does taking a K2 supplement make sense?
Let’s break it down.
Vitamin K is actually a family of related compounds. The two main forms found in the diet are vitamin K1 and vitamin K2.
Vitamin K1, or phylloquinone, is found primarily in leafy green vegetables and is the main dietary form of vitamin K.
Vitamin K2, or menaquinone, includes several different forms, including MK-4 through MK-13. Some forms are found in fermented foods and animal products, while MK-4 can also be produced by the body from vitamin K1.
Vitamin K helps activate several proteins involved in blood clotting and bone metabolism. Two of the most studied are osteocalcin, a protein found in bone, and matrix Gla-protein (MGP), which is found in tissues including blood vessels.
This is one reason vitamin K2 has attracted so much interest in research on bone and cardiovascular health.
If you’ve looked at a vitamin K2 supplement, you’ve probably noticed that it usually contains either MK-4 or MK-7.
Both are forms of vitamin K2, but they have different properties.
MK-4 is naturally present in some animal foods and can also be produced by the body from vitamin K1.
MK-7 is commonly found in fermented foods, particularly natto, and is widely used in dietary supplements. Research has found that MK-7 is well absorbed and remains in circulation longer than vitamin K1.
That doesn’t necessarily mean one form is universally “better.” They are simply different forms of vitamin K2 that have been studied in different ways.
This is where vitamin K2 gets a little more complicated.
It’s common to see claims online that most people are deficient in vitamin K2 or that a typical diet doesn’t provide enough. But clinically significant vitamin K deficiency is actually rare in healthy adults.
The body also gets vitamin K from a variety of foods, and some vitamin K is produced by bacteria in the gut.
For adults, the current adequate intake for total vitamin K is 120 mcg per day for men and 90 mcg per day for women. These recommendations apply to vitamin K overall rather than to K2 specifically.
That distinction matters because there isn’t a separate established daily requirement specifically for vitamin K2.
Some people may have difficulty getting or absorbing enough vitamin K, particularly those with certain digestive or malabsorption conditions or people taking medications that interfere with vitamin K metabolism.
For most healthy people, though, the goal should be to get adequate vitamin K as part of an overall nutritious diet rather than assuming that everyone is deficient in K2.
One of the most interesting areas of vitamin K2 research is bone health.
Vitamin K is required to activate osteocalcin, a protein involved in bone mineralization. This has led researchers to investigate whether vitamin K2 supplementation can support bone strength and reduce osteoporosis risk.
Some clinical research has found improvements in bone-related markers and measures of bone mineral density with vitamin K2 supplementation, particularly in postmenopausal women. However, results aren’t completely consistent, and it’s still unclear whether taking vitamin K2 supplements prevents osteoporosis or fractures in the general population.
That doesn’t make vitamin K unimportant.
It simply means we should distinguish between vitamin K’s established role in normal bone biology and the still-developing evidence around high-dose K2 supplementation.
For strong bones, vitamin K is only one piece of the picture. Adequate calcium, vitamin D, resistance exercise, physical activity, and overall nutrition all matter as well.
Vitamin K2 is also being studied for its potential connection to cardiovascular health.
One reason is MGP, a vitamin K-dependent protein involved in regulating calcification in tissues. Researchers are interested in whether adequate vitamin K status may help maintain healthy blood vessels.
There is some observational and clinical research suggesting a possible relationship between vitamin K status and vascular calcification. However, controlled trials have not consistently shown that vitamin K supplementation prevents arterial calcification, atherosclerosis, or arterial stiffness.
In other words, the biology is interesting, but it’s too early to say that taking K2 protects your heart or prevents calcium from building up in your arteries.
That’s an important distinction when looking at supplement claims online.
Vitamin K2 may have an interesting role in vascular health, but more research is needed to understand what supplementation means for long-term cardiovascular outcomes.
You may also see vitamin K2 supplements marketed for dental health.
The interest comes partly from vitamin K’s role in calcium-related proteins and bone metabolism. However, there isn’t enough strong human evidence to say that K2 supplements prevent cavities or significantly improve dental health.
For now, it’s better to view dental claims surrounding K2 as an area of ongoing research rather than an established benefit.
Good oral hygiene, regular dental care, adequate nutrition, and limiting frequent exposure to sugary foods and drinks remain much more established ways to support healthy teeth.
Vitamin K2 and vitamin D3 are often combined in supplements because both nutrients are involved in processes related to calcium and bone health.
Vitamin D helps the body absorb calcium and plays an important role in maintaining healthy bones and muscles. Vitamin K helps activate proteins involved in bone metabolism.
Because of these overlapping roles, it’s reasonable to be interested in how the two nutrients work together.
But there’s an important distinction between biological interaction and proven supplementation benefits.
Taking vitamin D3 without K2 has not been shown to automatically cause calcium to accumulate in your arteries, and K2 should not be presented as something that “redirects” calcium away from your blood vessels.
Rather than thinking of D3 and K2 as a mandatory combination, think of them as two nutrients with different but related roles in maintaining normal calcium and bone physiology.
Vitamin K2 is found in a variety of foods, although the amount can vary considerably depending on the food.
Some sources include:
Vitamin K1 is much more abundant in leafy green vegetables such as spinach, kale, collard greens, and broccoli.
This is another reason not to think about vitamin K2 in isolation. A varied diet can provide different forms of vitamin K along with the other nutrients your body needs.
For many people, getting nutrients from a varied diet is the best place to start.
A K2 supplement may be something to discuss with a healthcare professional if your diet is limited, you have a condition that affects nutrient absorption, or you have another specific reason to consider supplementation.
If you do choose a supplement, you’ll commonly see MK-7 used in products because it is well absorbed and has a relatively long half-life in the body.
Because vitamin K is fat-soluble, taking a supplement with a meal that contains some dietary fat can support absorption.
There isn’t one universally established K2 dose that every healthy adult needs, so be cautious of products that present a specific amount as the required target for everyone.
More isn’t necessarily better.
Vitamin K is generally considered to have a low potential for toxicity, and the National Academies did not establish a tolerable upper intake level for vitamin K.
However, there is one especially important interaction to know about.
Vitamin K can interact with warfarin and similar anticoagulant medications.
If you take warfarin, sudden changes in the amount of vitamin K you consume from food or supplements can affect how the medication works. People taking these medications should keep their vitamin K intake consistent and discuss any new supplement with their healthcare professional.
Certain other medications and health conditions can also affect vitamin K absorption or status.
If you’re taking prescription medication or have a condition that affects nutrient absorption, it’s worth checking with your healthcare professional before adding a vitamin K2 supplement.
Vitamin K2 may not get as much attention as vitamins D or C, but it plays an interesting role in the body as part of the broader vitamin K family.
Research has connected vitamin K to bone metabolism and has sparked interest in the potential role of K2 in cardiovascular health. At the same time, some of the strongest claims you’ll see online — especially claims that K2 prevents arterial calcium buildup or that everyone needs to supplement with it — go beyond what the current evidence can support.
The best approach is to focus on the basics first: eat a varied diet, get adequate nutrients, stay active, and use supplements thoughtfully when there’s a reason to do so.
Vitamin K2 is an interesting nutrient worth understanding. It just doesn’t need exaggerated claims to make it interesting.
— Eabha Organics
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