Vitamin K is an essential nutrient for overall well-being, particularly in activating proteins involved in blood clotting and maintaining bone integrity. It exists primarily in two forms: vitamin K1 (phylloquinone), and vitamin K2 (menaquinones).1
Vitamin K2 exists in several subforms, which are designated as menaquinone-4 (MK-4) through MK-13. MK-7 through MK-13 are primarily produced by bacterial fermentation in your gut. They’re also found in fermented foods such as natto, certain cheeses, sauerkraut, and some fermented dairy products.
Unlike other menaquinones, MK-4 is not typically produced by gut bacteria. Instead, it is primarily found in animal-based foods such as eggs, dairy products (like cheese and butter), and certain meats (especially liver).
The distinction between vitamin K1 and K2 goes beyond their dietary sources; it extends to their specific functions within your body. Vitamin K1 primarily facilitates blood coagulation, a vital process that prevents excessive bleeding when injuries occur. In contrast, vitamin K2 plays a more significant role in bone and cardiovascular health, guiding calcium to your bones and away from your arteries.
While both forms are indispensable, vitamin K2 is particularly noteworthy for its ability to prevent vascular calcification and enhance bone density. By promoting the carboxylation of proteins like osteocalcin and matrix Gla-protein (MGP), vitamin K2 helps prevent hardening of arteries and supports strong, healthy bones.
Carboxylation refers to a process that modifies specific amino acids, enabling the proteins to effectively bind calcium. The dual action of vitamin K2 makes it important for maintaining heart health and preventing osteoporosis, a condition marked by fragile bones.
Many people are lacking in vitamin K, but conventional methods of assessing its levels in the body are inadequate. Common tests, such as measuring prothrombin time — or how quickly your blood clots — primarily reflect vitamin K1 activity in your liver and fail to account for the essential roles of K2 in other tissues. Moreover, individual differences in absorption and metabolism of vitamin K complicate accurate assessment, making it difficult to determine specific supplementation needs.
Symptoms of vitamin K deficiency, like easy bruising or bleeding, are often mistaken for other conditions, leading to misdiagnosis. The absence of standardized tests for vitamin K2 further hinders the accurate diagnosis of deficiencies, resulting in missed opportunities for early intervention and prevention of related health issues.
The Superior Benefits of Vitamin K2
A review published in the International Journal of Molecular Sciences explored the distinct roles and advantages of vitamin K2 compared to vitamin K1, shedding light on why K2 is increasingly recognized as essential for comprehensive health.2
The research investigated how vitamin K1 and K2 differ in their absorption, distribution and overall impact on your body. Vitamin K2 stands out for its superior ability to enhance bone density. While K1 is necessary for blood clotting, K2 actively promotes the activation of osteocalcin, a protein that binds calcium to your bone matrix, thereby strengthening bones and reducing your risk of fractures.3
This functional difference underscores why K2 is more effective in improving bone quality compared to K1. Moreover, vitamin K2 plays a pivotal role in preventing arterial calcification, a process where calcium deposits build up in your arteries, leading to atherosclerosis. Unlike K1, K2 ensures that calcium is directed to your bones rather than accumulating in your vascular system, thereby maintaining arterial flexibility and reducing your risk of heart disease.4
The structural differences between vitamins K1 and K2 contribute to their varying absorption rates and bioavailability. Vitamin K2, especially in the MK-7 form, has a longer half-life in the bloodstream, allowing it to remain active in your body for extended periods. This prolonged presence enables K2 to be more effective in regulating calcium distribution and supporting extra-hepatic tissues such as bones and blood vessels.5
Furthermore, vitamin K2 has been linked to a lowered cancer risk, a benefit not observed with K1. Studies have shown that higher intake of vitamin K2 is associated with reduced incidence of certain cancers.6 Biologically, vitamin K2 influences several cellular pathways, including protein kinase A and C, which are involved in cell growth and immune response.
Additionally, K2 supports neuronal health through the P38 MAP kinase pathway, offering protective effects against neurodegenerative conditions.7 The review emphasized that vitamin K2 supplementation, particularly in the MK-7 form, is effective in managing osteoporosis, atherosclerosis and inflammatory diseases without the risk of negative side effects or overdosing. This safety profile makes K2 a reliable option for long-term health maintenance.8
Bioavailability and Efficacy of Vitamin K Forms
Another paper, published in the journal Foods, explored the distinct biological activities and absorption rates of vitamin K1 and K2, aiming to determine their relative efficacy in promoting bone and cardiovascular health.9 It was found that vitamin K2, particularly in the MK-7 form, exhibits higher bioavailability compared to vitamin K1 derived from green leafy vegetables like spinach and kale.10
Vitamin K2 is more efficiently absorbed and remains in your bloodstream longer, enhancing its effectiveness in various bodily functions. For example, the long-chained menaquinones MK-7 remains present in your plasma for up to 96 hours after ingestion, significantly longer than vitamin K1 and MK-4, which only stay in your plasma for eight to 24 hours.11
This extended presence allows vitamin K2 to have a more sustained impact on bone and cardiovascular health, as it can continuously support the activation of proteins that regulate calcium distribution in your body. The study also highlighted that both vitamin K1 and MK-7 inhibit the decline in bone mineral density. However, the benefits for cardiovascular health were observed exclusively with long-chain menaquinones like MK-7.12
This indicates that while both forms are beneficial for bone health, vitamin K2 has an added advantage in preventing arterial calcification, a key factor in reducing your risk of heart disease. Further, vitamin K2 was shown to be more effective in reducing uncarboxylated osteocalcin, a marker of bone health, compared to vitamin K1.13
The enhanced ability of vitamin K2 to activate osteocalcin underscores its superior role in bone metabolism. The review also explored the molecular mechanisms underpinning these differences, showing that vitamin K2 activates the pregnane X receptor (PXR), which regulates the transcription of genes responsible for extracellular matrix protein synthesis, thereby promoting collagen formation in osteoblasts.14
Vitamins K1 and K2 Differ in Transport and Absorption
Another significant aspect of the study was the comparison of transport mechanisms between vitamins K1 and K2. Vitamin K1 is primarily transported in lipoproteins rich in triacylglycerols (TGRLP) and, to a lesser extent, in high-density lipoproteins (HDL) and low-density lipoproteins (LDL).15
In contrast, vitamin K2’s various forms use different lipoprotein carriers for transportation. MK-4 is uniformly distributed across all lipoprotein types, for instance, while MK-9 transitions from TGRLP to LDL over time.16
The sequential transport — from TGRLP to LDL — contributes to the prolonged presence of long-chain menaquinones like MK-7 and MK-9 in the bloodstream, enhancing their bioavailability and effectiveness in the body. For example, MK-7 from natto was found to accumulate in the serum at concentrations several times higher than those of vitamin K1.17
The research also addressed the absorption process of these vitamins. Vitamin K1 is absorbed mainly in the proximal part of the small intestine in the presence of bile acids, whereas there is limited data on the molecular mechanisms of vitamin K2 absorption.18
However, it’s suggested that vitamin K2 is absorbed into your body through a simple movement in the last part of your small intestine and the beginning of your large intestine. This absorption is influenced by the amount of bile salts, certain types of fats and the acidity levels in your gut.
Overall, the study highlights the differences between vitamins K1 and K2, particularly in their bioavailability and specific health benefits. By demonstrating that vitamin K2 offers greater efficacy in bone density enhancement and arterial health maintenance, the research supports the growing preference for vitamin K2 supplementation in preventive health strategies.19
Understanding K1 to K2 Conversion and Absorption
It’s well-established that your body can convert vitamin K1 into vitamin K2, but this process isn’t very efficient on its own. In practical terms, that means you need significantly more K1 than standard dietary recommendations suggest to yield meaningful amounts of K2. While a typical daily requirement might be around a tenth of a milligram, taking K1 in much larger quantities, on the order of grams, can boost the amount of K2 your body generates.
However, there’s an important consideration: both vitamin K1 and K2 are fat-soluble. To optimize absorption, they’re best taken with meals that contain healthy fats. Emerging formulations are exploring even more efficient delivery methods, such as liposomal technologies, to help ensure that these nutrients are absorbed and utilized effectively.
In fact, a new product is on track to launch in the coming months that brings all these elements together: a high-dose of K1 (around 3 grams) combined with both MK-4 and MK-7 forms of K2, all designed with advanced delivery systems for maximum benefit. Such an approach aims to make it easier for individuals to access and utilize the full spectrum of these important vitamins.
Vitamin K’s Wide-Reaching Health Impacts
A scientific review published in Current Issues in Molecular Biology also explored the extensive roles of vitamin K in maintaining overall health, focusing on its impact on your brain, heart, bones and immune system.20 The research sought to understand how vitamin K contributes to these bodily functions and how it interacts with other essential nutrients to enhance health benefits.
The study involved a diverse group of participants, including healthy adults and individuals managing chronic health conditions. Findings revealed that vitamin K is important for roles beyond blood clotting, including brain health, cardiovascular function, bone strength and immune response.
Participants who maintained optimal levels of vitamin K2 had better cognitive function, stronger bones, healthier heart arteries and a more robust immune system compared to those with lower vitamin K2 levels.
The review also explored the synergistic relationship between vitamin K2 and vitamin D. When taken together, these vitamins amplify each other’s benefits, particularly for the circulatory and skeletal systems.21 It also revealed vitamin K2’s antioxidant properties, which help protect cells from damage caused by free radicals — unstable molecules that harm cells and contribute to aging and diseases.
Additionally, vitamin K2 has anti-inflammatory effects, reducing your body’s inflammatory response that leads to chronic conditions like heart disease and arthritis.22 By mitigating inflammation, vitamin K2 helps prevent the progression of these diseases, thereby supporting long-term health. Vitamin K2 also supports brain health.
The review noted that adequate levels of vitamin K2 are associated with better cognitive performance and a lower risk of neurodegenerative diseases. The antioxidant properties of vitamin K2 protect brain cells from oxidative stress, which is linked to conditions like Alzheimer’s and Parkinson’s diseases.
By maintaining a healthy brain environment, vitamin K2 contributes to improved memory, learning and overall cognitive function.
How to Get More Vitamin K2 in Your Daily Diet
Ensuring adequate intake of vitamin K, particularly through K2-rich foods and supplements, can significantly enhance overall health and reduce the risk of chronic diseases.23 K2, in particular, provides distinct advantages for bone density, heart health and cancer prevention over K1. To optimize your K2 intake, consider the following strategies:
1. Choose high-quality animal products — Opt for grass fed and pasture-raised animal products such as egg yolks, tallow and organ meats like liver. These sources provide significant amounts of vitamin K2.24
2. Include specific cheeses — Incorporate cheeses like Gouda and Brie into your diet, as they have high K2 content.25 Select cheeses made with animal rennet instead of GMO alternatives.
3. Incorporate fermented foods — Add fermented foods such as natto to your meals. Natto is a traditional fermented soybean product that boasts the highest concentration of highly absorbable MK-7 vitamin K2.26
4. Optimize food pairings for better absorption — Consume your K2-rich foods alongside healthy fats for optimal absorption. Also consider synergistic nutrients like vitamin D3 and magnesium.
5. Supplement with MK-7 — If you’re not getting enough vitamin K2 via dietary sources, incorporate a high-quality MK-7 vitamin K2 supplement into your daily regimen. MK-7 is highly bioavailable and effectively supports calcium metabolism, bone health and cardiovascular protection. Most adults need about 150 to 200 micrograms of vitamin K2 daily.
Egg Yolks Are Your Best Source of Vitamin K2 as MK-4
Of the foods highlighted above, egg yolks are among the highest dietary sources of MK-4, a vital form of vitamin K2 that plays a crucial role in bone health, cardiovascular function, and calcium regulation. Including egg yolks in your diet can significantly contribute to your MK-4 intake, supporting various aspects of your health.
You just need to be careful about your egg sources as most commercial egg sources — even free-range organic — have high PUFA levels as they are fed grains like soy and corn. Ideally, chickens should be fed rice, barley and split peas. I personally eat six egg yolks a day from chickens who are fed this and have 80% less linoleic acid than regular chickens.
Below is a comprehensive overview of egg yolks as a top source of MK-4, along with additional dietary sources and considerations.
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