How Common Is Vitamin K2 Deficiency?

November 22, 2025 •

4 min read

According to research, up to 97% of older adults in Western populations may have insufficient or deficient levels of Vitamin K2, making it a surprisingly common issue. This fat-soluble vitamin, often overshadowed by its more common counterpart K1, plays a critical role in bone and cardiovascular health. Understanding how common is Vitamin K2 deficiency and its implications is the first step toward better health.

Quick Summary

This article explores the prevalence of Vitamin K2 insufficiency, its potential health consequences for bone and heart health, and key dietary sources.

Key Points

Prevalence: Up to 97% of older adults in Western countries may be deficient or insufficient in Vitamin K2 due to modern dietary habits.
Role in Calcium Metabolism: Vitamin K2 activates proteins that direct calcium to bones and away from arteries, a process vital for long-term health.
Distinct from Vitamin K1: K2 (menaquinone) is found in fermented and animal-based foods and is better absorbed and distributed throughout the body than K1 (phylloquinone).
Health Risks of Deficiency: Insufficiency can contribute to bone loss (osteoporosis) and arterial calcification, increasing the risk of cardiovascular disease.
Key Sources: Rich sources include natto, certain cheeses (Gouda, Brie), fermented foods, egg yolks, and liver.
Synergy with Vitamin D: K2 and Vitamin D work together, with D absorbing calcium and K2 directing it. Combining them can enhance bone and heart health.
High-Risk Groups: Those with malabsorption issues, on certain medications like warfarin, and following vegan or vegetarian diets are at increased risk.

Unpacking the Prevalence of Vitamin K2 Deficiency

While severe Vitamin K deficiency causing excessive bleeding is rare in healthy adults, a widespread insufficiency of Vitamin K2 is far more common, especially in Western populations. Unlike Vitamin K1, which is primarily responsible for blood clotting and is abundant in leafy greens, Vitamin K2 has distinct functions crucial for bone and heart health. A recent study involving 452 healthy U.S. adults found a staggering 97% were either deficient or insufficient in Vitamin K2. This widespread issue stems from several factors, primarily the modern dietary shift away from traditional K2-rich foods.

Historically, diets in many cultures included significant amounts of fermented foods, organ meats, and high-fat dairy, which are excellent sources of Vitamin K2. However, Western diets now contain far fewer of these foods. For instance, while natto (fermented soybeans) is a staple in some Asian diets and a potent source of K2, it is not widely consumed in Europe or North America. Vegetarians and vegans are particularly at risk, as many of the richest K2 sources are animal-based.

The Crucial Functions of Vitamin K2

Vitamin K2 plays an essential role in activating specific proteins that manage calcium throughout the body. This is often described as working in tandem with Vitamin D. While Vitamin D helps the body absorb calcium, Vitamin K2 directs that calcium to where it is needed—the bones—and away from where it can cause harm, like the arteries and soft tissues.

Impact on Bone and Cardiovascular Health

Bone Mineralization: Vitamin K2 activates osteocalcin, a protein that binds calcium to the bone matrix, supporting bone formation and strength. A deficiency leads to inactive osteocalcin, which can weaken bones and increase fracture risk.
Arterial Decalcification: It also activates Matrix Gla Protein (MGP), which prevents calcium from depositing in blood vessels. Inactive MGP due to K2 insufficiency can contribute to arterial stiffness and cardiovascular disease.

Identifying Risk Factors for Deficiency

Several factors can increase an individual's risk of Vitamin K2 deficiency beyond a poor diet:

Malabsorption Conditions: Disorders that impair fat absorption, such as celiac disease, Crohn's disease, cystic fibrosis, and liver disease, can reduce the uptake of fat-soluble vitamins like K2.
Medications: Certain medications, including long-term use of broad-spectrum antibiotics and anticoagulant drugs like warfarin, can interfere with Vitamin K absorption or metabolism.
Dietary Choices: Vegans and individuals with low consumption of fermented foods, high-fat dairy, and organ meats have a much higher risk of deficiency.

The Difference Between K1 and K2

Understanding the distinction between Vitamin K1 (phylloquinone) and Vitamin K2 (menaquinone) is vital for understanding their different roles in health. While the body can convert a small amount of K1 to K2, the process is often inefficient, making dietary K2 intake important.

Comparison of Vitamin K1 vs. Vitamin K2


Feature	Vitamin K1 (Phylloquinone)	Vitamin K2 (Menaquinone)
Primary Function	Blood clotting	Calcium regulation for bone and heart health
Key Food Sources	Leafy greens (spinach, kale, broccoli) and some plant oils	Fermented foods (natto, sauerkraut), animal products (egg yolks, liver, certain cheeses)
Absorption	Poorly absorbed from plants; liver preferentially uses it for coagulation proteins	Better absorbed, especially MK-7; longer half-life, allowing it to reach extra-hepatic tissues
Target Tissues	Primarily the liver	Bones, blood vessels, brain, kidneys

Boosting Your K2 Levels Through Diet and Supplementation

To address widespread K2 insufficiency, focusing on dietary sources is key, especially since many common K2 foods are no longer staples in Western diets. A balanced approach that incorporates both healthy K1 and K2 sources is ideal. Here is a list of foods to consider:

Natto: This Japanese fermented soybean dish is the most potent dietary source of K2 (MK-7).
Hard and Soft Cheeses: Gouda, Brie, and other aged cheeses contain significant amounts of K2.
Sauerkraut: Fermented cabbage is a probiotic food that contains moderate amounts of K2.
Egg Yolks: An excellent source of K2, though moderation is key due to fat and cholesterol content.
Chicken Liver: This organ meat provides a concentrated source of K2 (MK-4).

For those with limited dietary options, supplementation with K2, particularly the highly bioavailable MK-7 form, can be an effective alternative. Combining a K2 supplement with Vitamin D is often recommended, as these two vitamins work synergistically to regulate calcium. For example, studies have shown that supplementing with Vitamin D, K2, and calcium can improve bone health and reduce fracture rates. It is important to consult a healthcare provider, especially if taking anticoagulant medication like warfarin, as K2 can affect blood clotting.

Conclusion

While historically underappreciated, Vitamin K2's role in maintaining long-term bone and cardiovascular health is becoming clearer. The prevalence of deficiency is surprisingly high, driven by modern dietary patterns that have excluded its primary sources. By understanding the distinction between K1 and K2 and the crucial functions of the latter, individuals can make informed dietary and lifestyle choices. Increasing intake of fermented foods and certain animal products, or considering supplementation, is a proactive step toward mitigating the significant health risks associated with insufficient Vitamin K2. Early awareness and intervention are essential for preventing complications like osteoporosis and arterial calcification and maintaining overall wellness.

Frequently Asked Questions

Diagnosing a Vitamin K2 deficiency is complex. While standard blood tests measure overall clotting time (PT/INR), a more sensitive measure involves assessing levels of uncarboxylated osteocalcin (ucOC) or Matrix Gla Protein (ucMGP), which rise when K2 is insufficient. A doctor may order these tests if they suspect an issue.

Unlike K1 deficiency, which causes bleeding, K2 deficiency symptoms are often silent and develop over time. They primarily include weakened bones and an increased risk of arterial calcification. Signs of severe deficiency may include easy bruising and excessive bleeding, though these are more typical of overall Vitamin K deficiency.

Both forms of Vitamin K are important for different functions. K1 is primarily for blood clotting and is abundant in leafy greens. K2 is crucial for bone and heart health and is found in fermented and animal-based foods. As K2 is less common in modern diets, ensuring adequate intake, especially of the MK-7 form, is often a priority.

It can be challenging to get optimal amounts of Vitamin K2 from a typical Western diet, which is low in key sources like natto, fermented dairy, and organ meats. A high intake of leafy greens provides K1, but not necessarily enough K2. Consciously incorporating K2-rich foods or supplementation may be necessary.

Individuals at high risk include those with malabsorption disorders (like Crohn's or celiac disease), liver disease, chronic kidney disease, and those on long-term antibiotic or anticoagulant therapy. Vegetarians and vegans may also be at risk due to a lack of animal-based K2 sources.

Vitamin K2 supplements are generally considered safe for most people, even at higher doses. However, it is essential to consult a healthcare provider before starting supplementation, especially if you take anticoagulant medication like warfarin, as K2 can affect blood clotting.

Yes, Vitamin K2 and Vitamin D work together synergistically. Vitamin D promotes calcium absorption from the gut, while Vitamin K2 is responsible for directing that calcium to the bones and preventing its deposition in arteries. Taking them together can maximize their combined benefits for bone and heart health.