What is vitamin K2?
Scientists first discovered vitamin K in 1929 as one of the factors essential for normal blood coagulation. In addition to its importance in blood clotting also plays a vital role in bone health, heart disease, and insulin sensitivity.
Vitamin K is essential for your body, but the human body can’t synthesize it, so you must obtain it from your diet.
There are many different forms of vitamin K, known as vitamers. Scientists have categorized them into three classes - phylloquinone (vitamin K1), menaquinones (vitamin K2), and menadione (vitamin K3).
Furthermore, vitamin K2 is not a single structure but a series of similar molecules known as menaquinones (MK). They range from MK-4 to MK-14, but the most important ones for human health are MK-4 and MK-7.
Vitamin K1 and K2 are natural vitamers, while vitamin K3 has an artificial origin and it’s toxic in high doses.
The most important, and the focus of discussion here are K1 and K2. Ensuring adequate intake of these vital but often overlooked vitamins for your heart and bone health.
The difference between vitamin K1 & K2
Vitamin K1 and the vitamers of vitamin K2 have significant differences in sources, effects, and dietary requirements.
Sources of vitamin K1 & K2
Vitamin K1 is the primary type of vitamin K found in most diets. The only dietary sources of this vitamer are plant foods such as dark leafy green vegetables. The richest sources you can add to your diet are parsley, kale, spinach, collard, and turnip greens.
To cover your daily needs, you need to consume about 50 mcg of vitamin K1, which you can easily obtain from food. For instance, 1 cup of broccoli can deliver more than 200 mcg.
Cooking does not damage vitamin K. On the contrary, studies show that microwaving broccoli doubles the bioavailability of the vitamin (1).
Besides, all forms of vitamin K are fat-soluble, so taking them alongside foods rich in fat significantly boosts its bioavailability. Adding fat such as oils to your dark leafy green vegetables rich in vitamin K1 will dramatically improve the absorption of the vitamin.
Nevertheless, phylloquinone has relatively low bioavailability that ranges from 5 to 10% (2). In comparison, the forms of vitamin K2, such as MK-4 and MK-7, have significantly better absorption.
While MK-4 has slightly better absorption than MK-7, the latter has a much longer half-life (up to several days), so even small doses can be effective (3).
Unfortunately, vitamin K2 is scarce in most diets. MK-4 is the form of vitamin K2 found in animal products such as egg yolks, beef, pork, and chicken. Chicken meat is the richest source, but it still contains only 25 mcg/100g, far lower than the effective daily dose - of 1500 mg of MK-4.
Bacteria, such as those found in fermented foods, are the only source of the remaining vitamin K2 forms - from MK-5 to MK-14.
The most important one to human health is MK-7.
The best source of MK-7 is a traditional Japanese food containing fermented soybeans called natto. Most hard and soft cheese types also have small amounts, but natto is the only reliable dietary source.
Unfortunately, most people have never consumed natto in their life, and even if they do, it’s unlikely they will start eating sufficient amounts of it daily. That is why most people are not consuming enough vitamin K2.
Effects of vitamin K1 & K2
Once absorbed in the gut, vitamin K1 has a short half-life, which means it doesn’t circulate in the blood for long before being used by the liver (4). Its benefits revolve mainly around supporting coagulation and blood clotting.
On the other hand, vitamin K2 and, more specifically, MK-7, has a much longer half-life. It circulates for days after a dose, and its benefits can reach more target tissues and organs such as your arteries and bones.
Due to its prolonged circulation, a dose of MK-7 can also effectively support blood clotting, and its effects on coagulation last for up to 4 days (5).
According to research, MK-7 also supports vitamin K status more effectively than MK-4 (6). The benefits of vitamin K2 extend to the bone tissue by activating two critical proteins called osteocalcin and matrix Gla that regulate bone growth, development, calcium uptake, and maturation (7).
Although MK-7 and Mk-4 activate these proteins, MK-7 appears more effective at lower doses (8). In comparison, vitamin K1 appears to have weaker effects on the risk of fractures and bone health, although it is not entirely ineffective.
These proteins stimulate bone strength and maturation by increasing calcium uptake inside bone tissue. This effect results in increased bone mineral density and reduced risk of osteoporosis and fractures.
According to a meta-analysis of randomized controlled trials, vitamin K2 lowers the risk of spinal fractures by 60%, hip fractures by 77%, and all other fractures by 81% (9).
That’s why the current guidelines recommend taking vitamin K2 for bone health (10).
The activation of osteocalcin has beneficial effects on insulin sensitivity. Several studies show that by activating osteocalcin, vitamin K2 can increase insulin sensitivity, lower blood sugar response to a meal, and improve glycemic control (11, 12).
Furthermore, activating the matrix Gla protein helps prevent calcification in other tissues such as blood vessels (13). That’s why vitamin K2 may help your cardiovascular health.
What is calcification of the arteries, and is it preventable?
Arterial calcification is a process that negatively affects your heart health. Calcium builds up in your arteries during arterial calcification, contributing to atherosclerosis and arterial stiffness.
Atherosclerosis is well known as the underlying cause of clogged arteries, heart attack, and stroke. Arterial stiffness leads to hypertension and also increases the risk of heart disease.
Scientists warn that calcification of the arteries is linked to an increased risk of death due to heart disease (14, 15). Research also links arterial calcification to increased all-cause mortality (16).
The studies also reveal that the risk applies to both the chronically ill and those without an apparent disease state. (17). Moreover, it is predictive of cardiovascular risk even in healthy people under 45 years.
The same proteins that regulate calcification of bone tissue, such as matrix Gla and osteocalcin, are also present in other tissues such as blood vessels and kidneys.
The role of the proteins in these tissues is to prevent the accumulation of calcium and direct it back into bone tissue.
Since vitamin K is a potent activator of these proteins, especially matrix Gla, scientists have investigated if the vitamin can stop or even reverse calcium buildup in arteries. As a result, most studies confirm the benefits of vitamin K2 for heart health.
In one trial that lasted more than 7 years, the people with the highest intake of vitamin K2 had more than 50% lower risk of developing artery calcification and dying from heart disease than those with inadequate intake (18).
Another trial in more than 16 000 women also reported that every 10 mcg of vitamin K2 the participants consumed daily reduced their risk of heart disease by 9% (19).
One recent meta-analysis collected data from 222 592 participants from all related studies so far confirms that higher dietary vitamin K consumption was associated with a moderately lower risk of heart disease (20).
Symptoms of vitamin K deficiency
If you have low vitamin K levels, it will affect the activity of the proteins that regulate calcium metabolism first. In contrast, only a severe deficiency will affect normal coagulation and blood clotting.
Studies report that insufficient vitamin K levels can increase the risk of osteoporosis, bone fractures, arterial calcification, and heart disease (21).
Scientists also suggest that patients with vitamin K deficiency are more likely to develop joint problems such as knee osteoarthritis (22). That’s because there is a matrix-Gla protein in cartilage as well, and by activating it, vitamin K prevents its calcification and the formation of osteophytes inside the joint.
Severe vitamin K deficiency leads to hemorrhages which can be potentially fatal. First, the bleeding occurs under the skin and inside muscles (23). Later on, the hemorrhages may occur anywhere inside or outside the body.
People with the highest risk of developing a deficiency include those on hemodialysis, causes of lipid malabsorption such as Celiac and Crohn's disease, dysbacteriosis due to prolonged therapy with broad-spectrum antibiotics, and older adults.
Should you combine vitamin K2 and D3
Combining vitamin D and K is preferable because they interact with the same proteins regulating calcium metabolism. For example, vitamin D synthesizes osteocalcin, while vitamin K is essential for its activation.
Similar to vitamin K2, there are very few good sources of vitamin D3. Besides, most experts recommend routinely supplementing with vitamin D since its deficiency is widespread.
Vitamin D improves calcium absorption and provides many health benefits, especially bone health (24).
Studies suggest that combining vitamin D3 and K2 enhances the benefits for bone health (25). Thus, vitamin D supplementation alongside your vitamin K supplement will reduce the risk of osteoporosis and bone fractures.
In addition, vitamin D toxicity which may occur with extremely high doses is thought to be due to exhaustion of vitamin K reserves. Vitamin D supplementation may even be dangerous if you have vitamin K deficiency since vitamin D elevates serum calcium concentration and may speed up the calcification of blood vessels.
Therefore, taking vitamin K supplement alongside vitamin D3 will minimize the risk of toxicity or side effects such as arterial calcification.
It is best to take a combined product such as Vitamin D3 + K2, which provides adequate amounts of both vitamins. If you have vitamin D deficiency, you may have to supplement with at least 50 mcg to normalize your vitamin D status.
Supplementing with vitamin K2 in the form of MK-7 is considered best as it has excellent absorption and the longest half-life. It is essential to supplement with at least 100 mcg daily to reap all the benefits of supplementation.
Benefits of supplementation
Supplementing with vitamin D3 and K2 can provide additional benefits:
- bone health
- heart health
- insulin sensitivity
Besides vitamin K's benefits for your cardiovascular system, studies show that Vitamin D supplementation can improve cardiovascular parameters and heart health (26).
Research reveals that vitamin D intake can also reduce the risk of insulin resistance and type 2 diabetes (27). Therefore, it also complements vitamin K’s insulin sensitivity and glycemic control benefits.
Vitamin D3 has additional benefits such as the reduced risk of some types of cancer and improved immune function. For example, one meta-analysis reports that supplementation reduced the risk of colorectal carcinoma by half (28).
Vitamin K2 reduces the risk of adverse effects from vitamin D supplementation and prevents or reverses arterial calcification, a significant risk factor for heart disease.
Vitamin D3 + K2 are two of the most synergistic and commonly deficient nutrients. Unless you have any contraindication against taking a vitamin K supplement, such as Warfarin therapy, you should consult your doctor and consider adding D3 + K2 supplements to your diet to boost cardiovascular, metabolic, and bone health.
Note: This article is for informational purposes only and not intended for use as medical advice. Always consult your healthcare provider before starting any dietary supplement.
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