Is vitamin K an antioxidant?

November 16, 2025 •

4 min read

While vitamin K is famously known for its role in blood coagulation, recent groundbreaking research has confirmed a potent, non-canonical function: it is a powerful antioxidant. This discovery significantly expands our understanding of how vitamin K works beyond clotting to protect the body at the cellular level.

Quick Summary

Recent research confirms vitamin K acts as a potent antioxidant, protecting cells from oxidative damage and inhibiting ferroptosis, a specific type of programmed cell death.

Key Points

Dual Function: Vitamin K is not only crucial for blood clotting but also acts as a potent antioxidant, a function independent of its coagulation role.
Prevents Ferroptosis: Its reduced form, vitamin K hydroquinone ($KH_2$), is a powerful inhibitor of ferroptosis, a type of cell death caused by iron-dependent lipid peroxidation.
Cellular Protection: Vitamin K protects lipid membranes from oxidative damage by effectively trapping oxygen radicals.
Neuroprotective Role: High concentrations of vitamin K, particularly MK-4, are found in the brain, where it protects against oxidative injury and supports mitochondrial health.
Antioxidant Mechanism: The enzyme FSP1 is responsible for reducing vitamin K to its active antioxidant form, demonstrating a unique, non-canonical cycle.
Beyond Standard Intake: While dietary recommendations focus on clotting, optimal cellular protection might require higher vitamin K status, though more research is needed.
Anti-inflammatory Effects: The antioxidant properties of vitamin K also contribute to its anti-inflammatory effects, which can help combat age-related diseases driven by chronic inflammation and oxidative stress.

The Dual Nature of Vitamin K: Beyond Coagulation

For decades, vitamin K was primarily recognized for its vital role in blood clotting (from the German word for coagulation, 'koagulation'). It serves as an essential cofactor for the enzyme $\gamma$-glutamyl carboxylase (GGCX), which activates several proteins necessary for healthy blood clotting. However, modern science is revealing a more complex story, unveiling a second, distinct function as a powerful antioxidant that operates independently of its clotting-related activity. This exciting discovery highlights vitamin K's significant potential in protecting the body against cellular damage and age-related diseases.

The Antioxidant Mechanism of Vitamin K

Unlike more traditional antioxidants like Vitamin C or E, which directly scavenge free radicals, vitamin K's antioxidant action is more nuanced and potent, especially in lipid membranes.

How Vitamin K Combats Oxidative Stress

Oxidative stress occurs when there is an imbalance between the production of damaging free radicals and the body's ability to neutralize them. Left unchecked, free radicals can damage cellular components, including lipids, proteins, and DNA, leading to a host of chronic health issues. Vitamin K's antioxidant mechanism works in several ways:

Free Radical Trapping: The key to vitamin K's antioxidant power lies in its reduced form, vitamin K hydroquinone ($KH_2$). This form is a potent, radical-trapping antioxidant that works directly within the cell's lipid bilayers to prevent the chain reaction of lipid peroxidation.
Ferroptosis Inhibition: Recent studies have identified vitamin K as a strong suppressor of ferroptosis, a specific form of programmed cell death characterized by iron-dependent lipid peroxidation. The reduced form, $KH_2$, acts as a defense against this process, effectively preventing the oxidative destruction of cellular membranes.
Enzymatic Support: A specific enzyme, ferroptosis suppressor protein 1 (FSP1), has been identified as playing a critical role in this process. FSP1 efficiently reduces vitamin K to its hydroquinone form, fueling a non-canonical vitamin K cycle that protects cells, independent of the classical clotting pathway.

Vitamin K and Cellular Protection

This antioxidant activity offers a range of protective benefits, particularly for sensitive tissues:

Neuroprotection: The brain contains high concentrations of vitamin K, particularly the K2 subtype (menaquinone-4, MK-4). Studies show that both vitamin K1 and MK-4 protect neurons and oligodendrocytes from oxidative injury, suggesting a neuroprotective role against conditions exacerbated by oxidative stress, like Alzheimer's and Parkinson's disease.
Mitochondrial Function: Vitamin K2 has been shown to support mitochondrial function and repair. By aiding electron transport and reducing reactive oxygen species (ROS) production, vitamin K2 helps maintain the health of these vital cellular powerhouses, which are particularly susceptible to oxidative damage.
Anti-inflammatory Effects: Oxidative stress is closely linked to inflammation. By modulating inflammatory signaling pathways, vitamin K exhibits anti-inflammatory effects that complement its antioxidant capabilities, potentially mitigating age-related chronic diseases.

A Comparison of Antioxidant Vitamins

While all fat-soluble vitamins offer some form of antioxidant protection, their mechanisms and potencies differ. The following table compares some key aspects of vitamin K and vitamin E based on available research.


Feature	Vitamin K (Hydroquinone)	Vitamin E (Tocopherol)
Primary Antioxidant Target	Primarily protects lipid membranes from peroxidation and inhibits ferroptosis.	Primary fat-soluble antioxidant, protecting cell membranes by scavenging lipid peroxyl radicals.
Mechanism of Action	Recycled via a specific non-canonical pathway involving FSP1; traps radicals within lipid bilayers.	Scavenges radicals and is regenerated by other antioxidants like Vitamin C.
Relative Potency	In some in vitro tests, it was shown to be about 80% as effective as vitamin E at equal concentrations.	Considered a highly potent and efficient scavenger of peroxyl radicals.
Solubility	Fat-soluble, protecting lipid-based structures like cell membranes.	Fat-soluble, functions effectively in cellular membranes.

Dietary Sources of Vitamin K

Both forms of vitamin K, K1 (phylloquinone) and K2 (menaquinones), have been shown to have antioxidant properties. They are found in different foods and have varying bioavailability.

Vitamin K1 (Phylloquinone) Sources:

Leafy green vegetables such as kale, spinach, collard greens, and broccoli.
Parsley.
Lettuce and cabbage.

Vitamin K2 (Menaquinones) Sources:

Fermented foods like natto (fermented soybeans), which is a rich source of MK-7.
Certain cheeses and dairy products.
Meat, eggs, and chicken.

Conclusion

While its function in blood clotting remains essential, recent scientific evidence firmly establishes that vitamin K is also a potent antioxidant, with mechanisms distinct from its clotting role. The discovery of its ability to trap free radicals in lipid membranes and inhibit ferroptosis opens new doors for understanding its protective effects against oxidative stress, neurodegeneration, and other cellular damage. This means that maintaining adequate vitamin K status through diet and potentially supplementation could be a valuable strategy for promoting overall cellular health and longevity.

For more insight, read the study on vitamin K's ability to inhibit oxidative injury to brain cells: Novel Role of Vitamin K in Preventing Oxidative Injury to Developing Oligodendrocytes and Neurons.

Frequently Asked Questions

Vitamin K, specifically its reduced form called vitamin K hydroquinone ($KH_2$), functions as an antioxidant by trapping oxygen radicals in cellular lipid membranes. This process is distinct from its clotting role and is facilitated by an enzyme called FSP1.

Vitamin K's clotting function relies on its role as a cofactor for the GGCX enzyme, which activates clotting proteins in the liver. The antioxidant function, however, operates independently through a non-canonical cycle involving the FSP1 enzyme and protects cell membranes from oxidative stress.

Yes, recent studies show that vitamin K is a potent inhibitor of ferroptosis, a specific form of programmed cell death caused by the accumulation of iron-dependent lipid hydroperoxides.

Both vitamin K1 and K2 have been shown to have antioxidant properties, but some research suggests that the menaquinone-4 (MK-4) form of vitamin K2 may be a more potent inhibitor of certain types of oxidative damage, particularly in brain tissue.

Dietary intake recommendations are based on levels needed for blood clotting, which may be lower than those required for optimal antioxidant protection. A balanced diet rich in K1 (leafy greens) and K2 (fermented foods, dairy) is beneficial, but further research is needed on specific dosages for antioxidant effects.

There is no established upper limit for vitamin K daily intake, and toxicity is rarely reported even with high supplemental doses. However, those on anticoagulant medications like warfarin must be cautious and consult a doctor, as high vitamin K intake can interfere with their treatment.

By acting as an antioxidant, vitamin K prevents oxidative injury to nerve cells and oligodendrocytes. It also supports mitochondrial function, regulates key signaling pathways, and helps maintain a healthy nervous system, potentially slowing cognitive decline.

Yes, research shows that vitamin E can interact with and influence the activity of vitamin K. The body's antioxidant network is complex, and these vitamins can work synergistically or influence each other's effects.