Does Vitamin K Reduce Inflammation? What the Evidence Shows

Vitamin K rarely makes headlines in the way that vitamin D or omega-3s do. Most people know it as the nutrient involved in blood clotting. What is less widely appreciated is that vitamin K acts as a cofactor for a whole family of proteins beyond the coagulation cascade, and several of those proteins appear to influence inflammation and immune regulation. Researchers have been piecing together this second story about vitamin K for roughly two decades, and the question of whether it genuinely reduces inflammation in humans has become progressively more interesting, and more complicated, as better trial data has emerged.

Vitamin K1 and Vitamin K2: Not the Same Thing

Understanding the vitamin K family matters because the different forms are not equivalent in the body. Vitamin K1, also called phylloquinone, is found almost exclusively in green leafy vegetables such as kale, spinach, Swiss chard, and Brussels sprouts. It is the predominant form in the Western diet and is processed primarily in the liver, where it supports clotting factor production. Most adults in developed countries get enough K1 to avoid deficiency in the classical sense.

Vitamin K2, the menaquinone family, behaves differently. The various K2 subtypes are named MK-4 through MK-13 according to the length of their side chain. MK-4 is found in eggs, meat, and some cheeses, and is synthesized from K1 in certain tissues. MK-7, the most studied long-chain form, is especially abundant in natto, a fermented Japanese soybean food, and is also found in other fermented cheeses. Critically, K2 has a longer half-life in the bloodstream than K1 and reaches tissues outside the liver at higher concentrations, including blood vessels, bone, and various immune tissues. This tissue distribution is one reason researchers have become particularly interested in K2 as a potential modulator of vascular inflammation and immune signaling.

The Biological Case: How Might Vitamin K Affect Inflammation?

The most studied pathway involves a protein called Matrix Gla Protein, or MGP. MGP is produced in blood vessel walls and cartilage, where its job is to prevent calcium from depositing in soft tissues. To do that job, MGP must first be activated by vitamin K-dependent carboxylation. When vitamin K status is inadequate, MGP stays in an undercarboxylated, inactive form often measured in blood tests as dp-ucMGP (dephospho-uncarboxylated MGP). High dp-ucMGP signals poor vitamin K activity in vascular tissue. The relevance to inflammation is that unactivated MGP is unable to inhibit calcification signals in vessel walls, and vascular calcification is itself a driver of local and systemic inflammation. Improving MGP carboxylation through better vitamin K status is therefore proposed as one indirect route by which vitamin K might lower inflammatory load.

A second pathway involves a protein called Gas6, or Growth arrest-specific 6. Gas6 is a vitamin K-dependent protein expressed in a range of cell types, including endothelial cells, smooth muscle cells, and several immune cell populations. Once carboxylated and activated, Gas6 binds to a family of receptor tyrosine kinases called TAM receptors (Tyro3, Axl, and MerTK). Activation of these receptors is now recognized as an important brake on innate immune responses: it helps resolve inflammation after a threat has been cleared, suppresses excessive cytokine production, and assists in the clearance of dead cells, a process called efferocytosis. A 2021 review published in Antioxidants summarized this body of work, noting that Gas6 and other vitamin K-dependent proteins act against age-related inflammatory processes and that adequate vitamin K is a prerequisite for their function (Popa et al., 2021).

Cell culture and animal studies add a third line of mechanistic evidence: direct suppression of inflammatory signaling. Several in vitro studies have shown that vitamin K2 can inhibit NF-kB, the master transcription factor that switches on genes for pro-inflammatory cytokines including IL-6 and TNF-alpha. Vitamin K2 also appears to have antioxidant activity independent of its carboxylation role, which could further restrain the oxidative stress that fuels inflammatory cascades. Animal studies of induced colitis have found that vitamin K-deficient mice develop more severe intestinal inflammation than well-supplied mice, with significantly higher IL-6 levels in the gut. A 2015 study from Osaka University found that vitamin K worked specifically to suppress IL-6 production in B immune cells, and that a K-deficient diet worsened disease severity in a standard mouse colitis model (Shiraishi et al., 2015). These preclinical findings build a plausible case, but they represent a lower standard of evidence than human trials.

What the Human Trials Actually Show

The human RCT data for vitamin K and inflammation presents a genuinely mixed picture, and honest reporting requires acknowledging both the promising signals and the clear null results. Several smaller trials have found improvements in inflammatory markers. A 12-week double-blind placebo-controlled trial published in the British Journal of Nutrition found that combined supplementation with vitamin D (5 micrograms), vitamin K (90 micrograms), and calcium (500 mg) twice daily in overweight type 2 diabetic patients with coronary heart disease produced a significant reduction in high-sensitivity CRP compared with placebo. The supplemented group showed an average hs-CRP change of approximately -1,320 ng/mL compared with +464 ng/mL in the placebo group, a statistically significant difference (Asemi et al., 2016). The limitation of this trial is obvious: because vitamin D, vitamin K, and calcium were all given together, attributing the CRP improvement specifically to vitamin K is not possible.

Trials that have isolated vitamin K2 supplementation in people with metabolic conditions have produced weaker results. A 12-week randomized trial in 60 patients with type 2 diabetes tested 200 micrograms per day of MK-7 against placebo. Within the MK-7 group, researchers observed statistically significant decreases in hsCRP, IL-6, and TNF-alpha over the 12 weeks. However, when the researchers compared the MK-7 group directly against the placebo group, the between-group differences in all three inflammatory markers failed to reach statistical significance. The authors concluded that further studies are needed and that MK-7 supplementation improved a marker of vitamin K status but did not demonstrably alter inflammatory status or body composition compared with placebo (Karamzad et al., 2022). This kind of result, where within-group improvement is visible but the between-group difference does not hold, is fairly common in smaller nutrition trials and is a reason for caution about interpreting before-and-after data without a proper control comparison.

The strongest challenge to the anti-inflammatory case for vitamin K comes from the AVADEC substudy, a large and rigorously designed trial published in 2025. In this randomized controlled trial, 388 men aged 65 to 74 who were at elevated cardiovascular risk received either a daily combination of 720 micrograms of vitamin K2 and 25 micrograms of vitamin D3, or a matching placebo, for 24 months. This is a substantially higher dose of K2 than most supplements provide, and the trial ran for long enough to expect meaningful changes if vitamin K does affect inflammation. The results were unambiguous: after 24 months, there were no statistically significant differences between groups in hs-CRP, IL-6, or TNF-alpha. The supplement did successfully reduce dp-ucMGP, confirming that it genuinely improved vitamin K status in vascular tissue. But that improved K status did not translate into measurable reductions in systemic inflammatory markers (Hasific et al., 2025). This is the most important single data point in the current vitamin K-inflammation literature, and it is a significant one.

Why the Results May Differ Across Trials

Several factors help explain why the smaller positive trials and the larger null trials do not simply contradict each other, but rather paint a more nuanced picture. Baseline vitamin K status matters enormously. If participants in a small trial happen to be genuinely low in vitamin K, correcting that deficiency can produce visible metabolic improvements. If participants already have adequate K status, additional supplementation is unlikely to change inflammatory tone, because the relevant proteins are already fully carboxylated and functional. The AVADEC trial enrolled elderly men who may have had sufficient dietary K intake in the first place, meaning the supplement may have produced benefit only for those who started deficient, diluting any effect across the full group.

The form of vitamin K used also matters. Most of the mechanistic rationale for anti-inflammatory effects centers on K2, particularly the long-chain forms like MK-7 that reach immune tissues in high concentrations. Trials using only K1, or combined supplements, are harder to interpret. Additionally, the dose, duration, and the specific population studied all influence outcomes. A high-dose supplement may produce different results in a patient with active inflammatory disease compared with a healthy older adult, and 12 weeks may not be long enough to show effects that a 24-month trial could detect, or fail to detect.

There is also the deeper question of which inflammatory endpoint matters most. CRP is a useful summary marker, but it reflects the output of many overlapping pathways. Vitamin K may affect specific localized processes, such as vascular wall inflammation or immune cell polarization, without necessarily moving the aggregate CRP number. The absence of a CRP effect does not rule out a benefit at the tissue level, though it does suggest that any benefit is unlikely to be large or consistent.

Food Sources and Who May Be Short

For most people eating a reasonably varied diet, K1 deficiency severe enough to impair coagulation or substantially raise inflammation is uncommon. Leafy green vegetables are the dominant K1 source, and regular consumption of spinach, kale, broccoli, or romaine lettuce provides plentiful phylloquinone. A single 100-gram serving of cooked kale, for instance, contains many times the adequate intake for an adult. Even people who do not eat abundant greens will typically get some K1 from vegetable oils and other foods.

Vitamin K2 status is a different story. Because fermented foods like natto are not widely eaten outside of Japan, and K2 from other sources such as aged cheese and eggs is modest, many people in Western populations may have suboptimal K2 status relative to what is needed to fully carboxylate proteins like MGP and Gas6. This is measurable via dp-ucMGP, and epidemiological data suggests that subclinical K2 insufficiency is common, particularly in older adults. Malabsorption conditions, long-term use of antibiotics that disrupt gut bacteria, and regular use of anticoagulant medications such as warfarin (which directly antagonizes vitamin K activity) also impair functional K status.

For people on warfarin specifically, vitamin K supplementation requires careful medical coordination. Because warfarin works precisely by blocking vitamin K activity, adding supplemental K can alter the drug's effectiveness and requires close monitoring of clotting times. This is a medical decision, not a wellness one.

Where Vitamin K Fits in an Anti-Inflammatory Strategy

The current evidence suggests a reasonable goal is dietary adequacy for K1 and a consistent effort to include K2-containing foods, rather than high-dose supplementation for a specific anti-inflammatory benefit. Leafy greens deliver K1 along with folate, fiber, magnesium, and polyphenols, all of which have their own roles in keeping inflammation in check. Fermented foods like certain cheeses, eggs, and other K2 sources overlap with broader dietary patterns associated with lower CRP. Eating these foods as part of a varied, whole-food diet is low-risk and likely supports general wellness in ways that extend beyond any one nutrient.

Isolated K2 supplements, particularly MK-7 at doses of 100 to 200 micrograms per day, appear safe for most adults without bleeding disorders or anticoagulant medications. Some people choose them specifically to improve vascular and bone Gla-protein carboxylation, which is a legitimate goal separate from the inflammation question. But the expectation of a measurable CRP drop from vitamin K supplementation is not well supported by the current clinical evidence, and the large AVADEC trial should recalibrate that expectation.

What anchors any real anti-inflammatory approach is the same set of variables that repeatedly moves CRP in clinical trials: body composition, quality sleep, aerobic fitness, reduced ultra-processed food intake, and management of chronic stress. Vitamin K nutrition belongs in the background of a solid dietary foundation, not in the foreground of a supplement protocol. For people who want to track how their lifestyle choices are actually affecting their inflammatory load, serial CRP measurement gives feedback that no supplement alone can provide. CRP is a general wellness marker rather than a diagnostic tool, and persistent or unexplained elevations are always worth discussing with a healthcare provider who can assess the fuller clinical picture.

Sources

• Popa DS, Bigman G, Rusu ME. The Role of Vitamin K in Humans: Implication in Aging and Age-Associated Diseases. Antioxidants (Basel), 2021. pubmed.ncbi.nlm.nih.gov/33917442
• Shiraishi E, Iijima H, Shinzaki S, et al. Vitamin K deficiency leads to exacerbation of murine dextran sulfate sodium-induced colitis. Journal of Gastroenterology, 2015. pubmed.ncbi.nlm.nih.gov/26314836
• Karamzad N, Faraji E, Adeli S, et al. The effect of menaquinone-7 supplementation on dp-ucMGP, PIVKAII, inflammatory markers, and body composition in type 2 diabetes patients: a randomized clinical trial. Nutrition and Diabetes, 2022. pubmed.ncbi.nlm.nih.gov/35365594
• Asemi Z, Raygan F, Bahmani F, et al. The effects of vitamin D, K and calcium co-supplementation on carotid intima-media thickness and metabolic status in overweight type 2 diabetic patients with CHD. British Journal of Nutrition, 2016. pubmed.ncbi.nlm.nih.gov/27198036
• Hasific S, Ravn EJ, Rasmussen LM, et al. Effects of vitamin K2 and D3 supplementation on epicardial adipose tissue and systemic inflammation: A substudy of the AVADEC trial. Atherosclerosis, 2025. pubmed.ncbi.nlm.nih.gov/41100911

Frequently Asked Questions

Does vitamin K reduce inflammation?

The evidence is mixed. Vitamin K activates proteins like Matrix Gla Protein and Gas6 that have biological roles in immune regulation and may reduce certain inflammatory signals. Some small trials have found improvements in hsCRP or IL-6 in people with metabolic conditions, but a large 24-month randomized controlled trial of high-dose vitamin K2 found no statistically significant effect on CRP, IL-6, or TNF-alpha. For most people, focusing on dietary adequacy rather than supplementing specifically for inflammation is the better-supported approach.

Is vitamin K1 or vitamin K2 better for inflammation?

The proposed anti-inflammatory mechanisms center more on vitamin K2, particularly long-chain forms like MK-7. K2 has a longer half-life and reaches immune and vascular tissues at higher concentrations than K1, which is processed predominantly in the liver for clotting. K2 also appears to inhibit NF-kB in cell studies and is needed to fully activate Gas6, which helps resolve immune responses. That said, neither form has strong clinical trial evidence for reducing CRP in otherwise healthy adults.

What foods are high in vitamin K?

Vitamin K1 is found mainly in leafy green vegetables such as kale, spinach, Swiss chard, broccoli, and Brussels sprouts. Vitamin K2 is found in fermented foods, especially natto (a fermented soybean product), and also in certain aged cheeses, eggs, meat, and butter from grass-fed animals. Most Western diets provide adequate K1 but relatively modest K2, since natto is not widely eaten outside Japan.

Can I take vitamin K2 as a supplement?

Vitamin K2 supplements, especially MK-7 at doses of 100 to 200 micrograms per day, are considered safe for most adults and are unlikely to cause harm. However, people taking warfarin or other vitamin K antagonist medications must not add vitamin K supplements without close medical supervision, as doing so can interfere with anticoagulant control. Anyone with a medical condition should discuss supplementation with their healthcare provider before starting.