Everything You Need to Know About Vitamin K2: Benefits, Sources & Health Impact

Vitamin K2 is an often-overlooked nutrient that plays a crucial role in maintaining your cardiovascular health, building strong bones, and supporting various bodily functions. While its more famous counterpart, vitamin K1, gets most of the attention for blood clotting, vitamin K2 works behind the scenes to direct calcium to where your body needs it most—your bones and teeth—while keeping it away from where it doesn’t belong, like your arteries.

Despite its importance, vitamin K2 remains one of the most under-consumed nutrients in the modern Western diet. Understanding the difference between vitamin K forms, recognizing the benefits of adequate K2 intake, and knowing which foods provide this essential nutrient can help you make informed decisions about your health and potentially reduce your risk of chronic diseases.

What Is Vitamin K2 and How Does It Differ from Vitamin K1?

Vitamin K was first discovered in 1929 when scientists identified it as a critical nutrient for blood coagulation—the medical term for blood clotting. The “K” comes from the German word “Koagulation.”

However, vitamin K isn’t just one substance. It exists in two primary forms:

• Vitamin K1 (phylloquinone): This form is predominantly found in plant-based foods, particularly leafy green vegetables like spinach, kale, and collard greens. K1 represents about 90% of the vitamin K in a typical Western diet and is primarily involved in blood clotting functions.
• Vitamin K2 (menaquinone): This form appears in animal-based foods, fermented foods, and is also produced by bacteria in your gut. K2 plays a more diverse role in the body, particularly in calcium metabolism, bone health, and cardiovascular protection.

Vitamin K2 can be further subdivided into several subtypes, designated as MK-4 through MK-13, based on the length of their side chain. The most important and well-studied subtypes are MK-4 and MK-7:

• MK-4: Found in animal products like meat, eggs, and dairy. It has a shorter half-life in the body, requiring more frequent consumption.
• MK-7: Found primarily in fermented foods, particularly natto (fermented soybeans). It has a longer half-life and remains active in the body for a longer period.

While your body can convert some vitamin K1 to K2, this conversion process is relatively inefficient. Only about 10-15% of dietary vitamin K1 is absorbed, and the conversion to K2 is limited. This makes obtaining K2 directly from food sources or supplements particularly valuable.

How Vitamin K2 Supports Heart Health

Cardiovascular disease remains the leading cause of death in the United States, and calcium buildup in the arteries—a condition known as arterial calcification—is a major contributing factor. When calcium deposits accumulate in your arterial walls, they cause the vessels to stiffen, reducing their flexibility and increasing the risk of heart attack and stroke.

Vitamin K2 plays a protective role by activating a protein called matrix GLA protein (MGP), which acts like a calcium traffic controller in your body. MGP binds to calcium and prevents it from depositing in your arterial walls, effectively keeping your blood vessels soft and flexible.

Research supports this mechanism:

• A comprehensive meta-analysis examining 21 studies with over 222,000 participants found that increased dietary intake of vitamin K—both K1 and K2—was associated with a moderately reduced risk of coronary heart disease.
• A subsequent review specifically examining vitamin K and coronary heart disease found that K2 supplementation showed the most promise for cardiovascular protection.
• Population studies have consistently shown that people with higher vitamin K2 intake tend to have less arterial calcification and lower rates of heart disease.

While these findings are promising, it’s important to note that most studies have been observational, which means they can show associations but not definitively prove cause and effect. Long-term controlled trials are still needed to confirm these benefits conclusively.

Nevertheless, the biological mechanism by which K2 protects against arterial calcification is well-established, and the consistent positive associations in population studies provide compelling evidence for its cardiovascular benefits.

Vitamin K2 and Bone Health: Building Stronger Bones

Osteoporosis affects millions of Americans, particularly postmenopausal women and older adults. This condition, characterized by porous, fragile bones, dramatically increases the risk of fractures, which can lead to decreased mobility, loss of independence, and reduced quality of life.

Vitamin K2 is essential for bone health because it activates osteocalcin, a protein produced by bone-building cells called osteoblasts. When osteocalcin is activated by K2, it can effectively bind calcium and incorporate it into the bone matrix, strengthening your skeletal structure.

Without adequate vitamin K2, osteocalcin remains inactive and cannot properly direct calcium into bones. This can lead to:

• Reduced bone mineral density
• Increased bone fragility
• Higher risk of fractures
• Potential calcium deposition in soft tissues instead of bones

Research on K2 and bone health has shown encouraging results:

• A meta-analysis of 16 studies involving over 6,400 postmenopausal women found that vitamin K2 supplementation had a positive effect on bone mineralization and increased bone strength.
• Studies conducted in Japan, where K2-rich natto is commonly consumed, have shown lower rates of hip fractures compared to Western countries with lower K2 intake.
• K2 supplementation has been associated with reduced bone loss in postmenopausal women.

However, more recent reviews have shown mixed results, with some studies demonstrating clear benefits while others show minimal effects. The discrepancies may be due to differences in study design, K2 dosage, duration of supplementation, and baseline vitamin K status of participants.

Despite the need for additional high-quality, long-term studies, the evidence suggests that adequate vitamin K2 intake is an important component of a comprehensive strategy for maintaining bone health throughout life.

Vitamin K2 and Dental Health

Your teeth are living structures that require proper nutrition to maintain their strength and integrity. Vitamin K2 plays a role in dental health through the same mechanisms that support bone health.

Osteocalcin, the protein activated by vitamin K2, is also found in dentin—the calcified tissue that makes up the bulk of your tooth structure beneath the enamel. Activated osteocalcin triggers mechanisms that promote the growth of new dentin and support overall tooth health.

Research has shown that:

• A study of nearly 5,000 elderly individuals found that regular vitamin K supplementation combined with moderate fiber intake was effective at helping prevent tooth loss from periodontal disease, particularly in males.
• Animal studies have demonstrated that vitamin K2 deficiency can lead to dental abnormalities and reduced tooth mineralization.
• Vitamin K2 works synergistically with vitamins A and D to support dental health, with all three nutrients playing complementary roles in maintaining healthy teeth and gums.

While research in this area is still emerging and more studies are needed, the biological mechanisms suggest that adequate vitamin K2 intake may contribute to maintaining strong, healthy teeth throughout your life.

Potential Role in Cancer Prevention

Some preliminary research has explored the relationship between vitamin K2 and cancer risk, though this area requires much more investigation before any definitive conclusions can be drawn.

Cell and animal studies have suggested that vitamin K2 may inhibit the growth of liver cancer cells. Some observational studies have found associations between K2 intake and reduced cancer recurrence rates in liver cancer patients.

However, the evidence is mixed and sometimes contradictory. Some studies have found associations between high MK intake and increased risk of certain cancers, while others have found protective effects.

It’s important to emphasize that this research is in very early stages. The studies conducted so far have been limited to cell cultures, animal models, and small observational studies in humans. Large-scale, well-controlled clinical trials are needed before any recommendations can be made regarding vitamin K2 for cancer prevention.

Best Food Sources of Vitamin K2

While vitamin K1 is abundant in many common vegetables, vitamin K2 is less prevalent in the typical Western diet, which may explain why many Americans don’t get enough of this important nutrient.

Animal-Based Sources

Vitamin K2, particularly the MK-4 subtype, is found in animal products, especially those from grass-fed animals:

• Grass-fed dairy products: Butter, cheese (especially aged varieties like Gouda and Brie), and whole milk from grass-fed cows contain significantly more K2 than conventional dairy products
• Egg yolks: Particularly from pasture-raised chickens, which contain higher levels of K2 than eggs from caged hens
• Liver and organ meats: Beef liver, chicken liver, and other organ meats are excellent sources
• Dark meat poultry: Chicken and turkey thighs contain more K2 than white meat
• Fatty fish: Salmon and other fatty fish contain moderate amounts

It’s important to note that vitamin K2 is a fat-soluble vitamin, meaning it’s found in the fatty portions of foods. Low-fat and fat-free versions of these foods will contain minimal amounts of K2.

Fermented Foods

Fermented foods contain the MK-7 and other longer-chain subtypes of vitamin K2, produced by bacterial fermentation:

• Natto: This traditional Japanese food made from fermented soybeans is by far the richest dietary source of vitamin K2, containing exceptionally high levels of MK-7. Just one serving can provide several times the recommended daily intake.
• Sauerkraut: Fermented cabbage contains modest amounts of K2
• Certain cheeses: Some fermented cheeses, particularly soft cheeses like Brie and aged cheeses like Gouda, contain beneficial amounts
• Miso: This fermented soybean paste used in Japanese cuisine contains K2
• Kimchi: This Korean fermented vegetable dish contains some K2

Gut Bacteria Production

Your intestinal bacteria, particularly those in your large intestine, can produce vitamin K2. However, the extent to which this bacterial production contributes to your overall vitamin K2 status remains unclear.

Some research suggests that broad-spectrum antibiotics may reduce K2-producing bacteria, potentially contributing to deficiency. Maintaining a healthy gut microbiome through probiotic-rich foods and adequate fiber intake may support your body’s natural K2 production.

Should You Consider Vitamin K2 Supplements?

Whether you need a vitamin K2 supplement depends on several factors, including your diet, age, health status, and risk factors for conditions like heart disease and osteoporosis.

Who Might Benefit from Supplementation?

• People who don’t regularly consume K2-rich foods
• Those following plant-based diets who don’t eat fermented foods
• Postmenopausal women at risk for osteoporosis
• Individuals with risk factors for cardiovascular disease
• People with fat malabsorption conditions that impair vitamin K absorption
• Those who have taken long courses of broad-spectrum antibiotics

Choosing a Supplement

If you decide to supplement, consider these factors:

• MK-7 vs. MK-4: MK-7 has a longer half-life and remains active in the body longer, potentially requiring less frequent dosing. MK-4 is the form found in animal products and may require higher doses.
• Combination supplements: Vitamin K2 works synergistically with vitamin D, and many supplements combine these two nutrients. This combination may enhance the benefits of both vitamins.
• Dosage: Common supplemental doses range from 45 to 180 micrograms per day, though some studies have used higher amounts.

Safety Considerations

Vitamin K2 has a very low potential for toxicity, and no tolerable upper intake level has been established. No adverse effects from high doses of K2 from food or supplements have been documented in research.

However, there is one important consideration: people taking blood-thinning medications should consult their healthcare provider before taking vitamin K supplements, as sudden increases in vitamin K intake can interfere with these medications. If you’re on anticoagulant therapy, maintaining consistent vitamin K intake is important for medication effectiveness.

Before starting any supplement regimen, it’s wise to consult with a healthcare professional who can assess your individual needs and potential interactions with medications or health conditions.

How Much Vitamin K2 Do You Need?

Currently, there is no separate recommended daily allowance specifically for vitamin K2. The Adequate Intake (AI) for total vitamin K is:

• Adult men: 120 micrograms per day
• Adult women: 90 micrograms per day

However, these recommendations were established primarily based on the amount needed for adequate blood clotting (a K1 function) and may not reflect the optimal intake for the broader health benefits associated with vitamin K2.

Some researchers suggest that the optimal intake of K2 for bone and cardiovascular health may be higher than current recommendations, but more research is needed to establish specific guidelines.

The Synergy Between Vitamins K2, D, and A

Vitamins K2, D, and A work together in complementary ways to support bone health, dental health, and calcium metabolism. Understanding this synergy can help you optimize your nutritional strategy:

• Vitamin D: Promotes calcium absorption from your digestive tract and stimulates the production of vitamin K-dependent proteins like osteocalcin and MGP
• Vitamin K2: Activates these proteins so they can direct calcium to bones and teeth while preventing calcium deposition in soft tissues
• Vitamin A: Works with D and K2 to regulate calcium metabolism and bone remodeling

This synergy means that having adequate amounts of all three vitamins may be more beneficial than having high levels of just one. Some experts suggest that the widespread vitamin D supplementation in recent years may have increased the need for adequate vitamin K2, as vitamin D increases the body’s production of K-dependent proteins that require K2 for activation.

Signs You Might Be Low in Vitamin K2

Unlike some nutrient deficiencies that cause obvious symptoms, vitamin K2 insufficiency often doesn’t produce immediate, noticeable effects. However, over time, inadequate K2 may contribute to:

• Easy bruising or bleeding (though this is more associated with overall vitamin K deficiency)
• Reduced bone mineral density over time
• Increased arterial calcification (which typically doesn’t cause symptoms until advanced)
• Dental problems

Because these signs develop gradually and can have multiple causes, vitamin K2 status is best assessed by evaluating your dietary intake and risk factors rather than waiting for symptoms to appear.

Practical Tips for Increasing Your Vitamin K2 Intake

Here are actionable strategies to boost your vitamin K2 consumption naturally:

1. Choose grass-fed dairy products: When possible, opt for butter, cheese, and dairy from grass-fed cows, which contain significantly more K2 than conventional products.
2. Include fermented foods regularly: Try incorporating sauerkraut, kimchi, or fermented cheeses into your meals. If you’re adventurous, natto provides exceptional amounts of K2.
3. Don’t fear egg yolks: The yolk is where the K2 resides, so include whole eggs in your diet, preferably from pasture-raised chickens.
4. Include organ meats occasionally: Liver and other organ meats are nutrient-dense sources of K2 and many other vitamins.
5. Choose full-fat over low-fat: Since K2 is fat-soluble, full-fat versions of dairy and other animal products contain more of this nutrient.
6. Support your gut bacteria: A healthy microbiome can produce some K2, so eat plenty of fiber and probiotic-rich foods.
7. Consider food pairings: Since K2 is fat-soluble, consuming it with dietary fats enhances absorption.

Common Questions About Vitamin K2

Can you get too much vitamin K2?

Vitamin K2 has a very low toxicity risk. No adverse effects from excessive intake have been documented, and no upper intake level has been established. However, this doesn’t mean unlimited amounts are advisable—moderation is always prudent with any nutrient.

Does cooking affect vitamin K2 content?

Vitamin K is relatively heat-stable, so normal cooking temperatures don’t significantly reduce K2 content in foods. However, exposure to light can degrade vitamin K, so storing K2-rich foods properly is important.

Is K2 from food better than supplements?

While getting nutrients from whole foods is generally preferable because foods provide a complex matrix of nutrients that work together, vitamin K2 supplements can be an effective way to ensure adequate intake, especially if your diet doesn’t include many K2-rich foods.

How long does it take to see benefits from K2?

The timeline varies depending on what health outcome you’re considering. Some markers of bone and cardiovascular health may take months to years to show measurable changes. K2’s effects are preventive and cumulative, working over time to support long-term health.

Do vegans and vegetarians need to worry about K2?

Since the richest sources of K2 are animal products and natto, people following plant-based diets may have lower K2 intake. However, the body can convert some K1 (abundant in leafy greens) to K2. Vegans and vegetarians who eat fermented foods like natto, tempeh, or sauerkraut, or who take K2 supplements, can maintain adequate levels.

The Bottom Line

Vitamin K2 is an essential nutrient that plays crucial roles in cardiovascular health, bone strength, dental health, and proper calcium metabolism. Unlike its better-known cousin vitamin K1, which is primarily involved in blood clotting, K2 acts as a calcium director, ensuring this important mineral goes where your body needs it—into your bones and teeth—while keeping it out of your arteries and soft tissues.

The modern Western diet is often lacking in vitamin K2, as the richest sources include foods that many people don’t consume regularly: grass-fed dairy products, organ meats, egg yolks, and fermented foods like natto. This widespread insufficiency may contribute to the high rates of osteoporosis and cardiovascular disease seen in developed countries.

While more research is needed to establish optimal intake levels and definitively prove all the proposed benefits, the existing evidence strongly suggests that ensuring adequate vitamin K2 intake is an important component of a health-promoting diet. Whether through food sources or supplementation, getting enough K2—along with its synergistic partners vitamins D and A—may help support your long-term bone, heart, and overall health.

If you’re concerned about your vitamin K2 status, consider evaluating your diet to see if you regularly consume K2-rich foods. If not, you might benefit from incorporating more of these foods into your meals or discussing supplementation with a healthcare provider who can help you determine the best approach based on your individual health needs and risk factors.

Sources:

• National Institutes of Health – Calcium buildup and heart disease risk
• PubMed – Vitamin K and calcium deposition prevention
• PubMed – Meta-analysis on vitamin K and coronary heart disease
• BMJ Open Heart – Vitamin K and coronary heart disease risk
• PubMed – Vitamin K2 and bone health meta-analysis
• MDPI Nutrients – Recent trials on vitamin K2 and bone health
• National Institutes of Health – Osteocalcin and dental health
• National Institutes of Health – Vitamin K2 and dentin growth
• PubMed – Synergy between vitamins A, D, and K
• PubMed – Vitamin K2 and liver cancer cells
• PubMed – Vitamin K2 and cancer recurrence
• National Institutes of Health – Vitamin K1 vs K2 dietary ratios
• Frontiers in Immunology – Gut bacteria and vitamin K2 production
• National Institutes of Health – Vitamin K2 food sources
• ScienceDirect – MK subtypes in different foods
• National Institutes of Health – Vitamin K2 and D synergy
• National Institutes of Health – Vitamin K and blood thinning medications