ALL YOU NEED TO KNOW ABOUT VITAMIN K

Medically Reviewed by Dr. Rosmy Barrios - September 25, 2024

Are you getting enough vitamin K in your diet? Current statistics suggest that up to one-third of individuals are not meeting their daily vitamin K needs^[1] and that this may reflect later on in the form of poor bone health, thrombotic disorders and heart disease.

The below article briefly reviews vitamin K’s contribution towards overall health, including its benefits, factors that promote deficiency, sources and supplementation, as well as contraindications.

What is Vitamin K?

Vitamin K, an essential fat-soluble vitamin, is mainly known for its role in facilitating bone health and blood coagulation. It is required for specific cellular reactions involving gamma-glutamyl carboxylase, which makes use of vitamin K in order to modify vital cellular proteins^[2]. Reactions requiring gamma-glutamyl carboxylase are known as carboxylation. Carboxylation allows for Vitamin K-dependent proteins to bind strongly to calcium ions in order to fulfill their functions. They regulate cellular growth, adhesion, calcium deposition, and blood coagulation.

11 Vitamin K Health Benefits 

Epidemiological studies highlight the importance of maintaining optimal vitamin K intake over the lifespan. While vitamin K is required for overall health, studies are still inconclusive as to whether supplementing vitamin K is beneficial over and above meeting the nutritional needs of the individual. This may be because when Vitamin K levels are insufficient, the body substitutes with other cellular enzymes to carry out some of vitamin K’s functions. However, these substitutions do not fully compensate for its activity in the body and can contribute to health problems in the long run.

Below are some of the few benefits ascribed to maintaining an adequate vitamin K intake^[3]:

1. Improves Long-Term Bone Mineral Density. In bone, carboxylation of osteocalcin changes its properties and functions. Fully carboxylated osteocalcin enhances bone mineral density by regulating bone matrix formation and calcium retention. Osteocalcin is also noted to enhance insulin release and sensitivity^[4]. Partially carboxylated osteocalcin may also improve insulin signaling. However, it contributes to faulty bone development. This can result in lowered bone mineral density and an increased risk for fractures. Preliminary studies suggest that it may contribute directly towards bone resorption as well. Adequate vitamin K intake across the lifespan is directly linked to improved bone mineral density.^[5]
2. Protects Against Fractures and Postmenopausal Osteoporosis. Adequate vitamin K status may help to prevent bone fractures and protect against osteoporosis, especially when coupled with sufficient magnesium, calcium and vitamin D intake. Long-term vitamin K2 supplementation may be beneficial for use in treating postmenopausal osteoporosis, as evidenced by studies that suggest it may slow down its progression.^[6]
3. Cardiovascular Calcification. Carboxylation is required to prevent cardiovascular and collagen calcification in the body. Higher levels of all uncarboxylated proteins are noted to contribute to the calcification of blood vessels and cartilage, which can exacerbate the severity of coronary heart disease and the risk of a heart attack. Vitamin K2 supplementation is associated with limiting calcification of the coronary artery, reducing the risk of coronary heart disease and decreases in related mortality.^[7] Additionally, elevations of uncarboxylated proteins have been found in samples from patients with osteoarthritis and fibrotic disorders.
4. Blood Coagulation. Vitamin K helps to regulate blood coagulation by activating both pro and anticoagulant factors.^[8] Adequate intake is known to enhance the production of these factors and lower the risk for thrombotic disease. The ability of this vital nutrient to help reduce the risk for arterial calcification contributes towards a lowered thrombosis risk.
5. Skin. Preliminary studies have shown that vitamin K can help to speed up wound healing when applied topically as 1% of an ointment.^[9] In rats, deficiency lowered the skin collagen content, which suggests that maintaining adequate intake may protect the skin from rapid aging.^[10]
6. Potential Kidney Stone Prevention. Nephrocalcin is another carboxylated protein that regulates calcium binding in the kidneys. When vitamin K status is normal, it binds to calcium oxalate and inhibits its crystallization and deposition in the kidneys. Patients with kidney stones display elevated levels of uncarboxylated nephrocalcin, yet research is lacking with regard to using Vitamin K in order to prevent kidney stone formation. Vegetarian diets high in vitamin K-rich foods are noted to help lower kidney stone formation in those at risk. Supplementation of Vitamin K2 may enhance kidney health outcomes for those with chronic kidney disease without any side effects.^[11]
7. May Improve Insulin Sensitivity. Those with type 2 diabetes may be at risk for vitamin K deficiency and may benefit from supplementation. A few studies suggest that relatively high doses of vitamin K2 (360mcg daily as MK7 for 12 weeks) substantially improved markers of glycemic control and enhanced insulin sensitivity without any adverse effects.^[12]
8. Brain Health and Cognitive Function. A small body of evidence suggests that vitamin K is vital for optimal cognition and may have a place in the prevention of neurodegenerative diseases. Vitamin K is important for the production of sphingolipids, which are crucial fats that comprise large portions of neuronal cell membranes that support neuronal cell growth and are involved in myelination. The activation of various vitamin K-dependent proteins, including anticoagulant protein S, has also been associated with lowering neuroinflammation. Lastly, vitamin K supplementation may help to protect against cognitive deficits seen in those on long-term warfarin.^[13]
9. Liver Protective and Potentially Anticarcinogenic. Vitamin K2 supplementation has been shown in a couple of trials to protect patients with liver cirrhosis from developing liver cancer.^[14] In vitro studies suggest that vitamin K may inhibit carcinogenesis in other cancer cell lines, including colonic cancer.
10. Antioxidant Effects. Vitamin K has been shown in vitro to inhibit several inflammatory markers associated with aging, inflammatory disease states and cancer^[15]. While it may help to lower inflammation as part of its usual actions in the body, supplementation has failed to show a significant benefit with regard to rheumatoid arthritis^[16].
11. Associated with Leading a Healthier Lifestyle. Those who consume adequate amounts of vitamin K are generally seen to be healthier on average and lead healthier lifestyles. This may be because foods high in the vitamin are typically plant-based, leafy greens that contain a whole host of other healthful nutrients as well.

Vitamin K Deficiency

Deficiency has been associated with promoting various states of disease, including growth abnormalities in infants, cardiovascular conditions, osteoporosis and bruising disorders. One large-scale 10-year trial revealed that insufficient vitamin K intake was linked with increasing all-cause and cardiovascular mortality rates.^[17]

Subclinical Vitamin K deficiencies are far more common than full-blown deficiencies, seen to affect between 8-31% of the global population.^[18] These usually affect elderly individuals and those at a higher risk for deficiency. As a result, symptoms of deficiency are rare and usually coupled with other health conditions.

Adequate Intake Levels. As Vitamin K is recycled in the body, very little is required from the diet or supplementation to maintain optimal levels. For men, the appropriate daily consumption of vitamin K is 120 mcg, and for women, it is 90 mcg. Vitamin K does not have an established upper limit.^[19]

Symptoms of Vitamin K Deficiency include heightened bleeding and bruising and may also include slow wound healing and poor skin quality. Severe deficiency may exacerbate symptoms of blood-clotting or bleeding disorders, osteoporosis and related conditions, or fibrotic diseases.

Deficiency Risk Factors. Low vitamin K levels are often the result of diminished intake, digestive issues, metabolic derangements or a health condition that impairs its use or absorption.

• Medications. Some anticoagulants, like warfarin, inhibit vitamin K and can block the ability of body tissues to recycle vitamin K, with long-term use resulting in a deficiency. Vitamin K supplementation may improve the ability of warfarin to thin the blood in those who take it long-term. Other medications that reduce vitamin K absorption include antibiotics, bile acid sequestrants and weight loss drugs like orlistat. Cephalosporin antibiotics may contribute to deficiency by blocking vitamin K in the body, besides destroying the gut bacteria that produce it.
• Newborns and Infants may be at a higher risk for vitamin K deficiency due to being born with low body levels, having an immature microbiome, and the fact that breast milk is often low in the nutrient. The risk for deficiency may be dependent on the vitamin K status of the mother, as formula-fed infants are less likely to develop deficiency.
• Disease states. Metabolic conditions that affect liver and fat metabolism may also disturb the distribution and use of vitamin K in the body. Chronic gut dysbiosis, intestinal infections and IBD may also increase the risk for vitamin K deficiency due to lower production and absorption.^[20] Vitamin K was found to be substantially higher in the fat mass of those with obesity, while the level of carboxylated coagulant factors was lower.^[21] While this is technically not a state of deficiency, the displacement of vitamin K may show up in diagnostic tests as a deficiency.

Forms and Sources of Vitamin K

The main forms of vitamin K include vitamin K1 and K2:

• Vitamin K1 is known as phylloquinone and is produced in plants. It can be found at the highest concentrations in leafy green vegetables as it is required for photosynthesis. Other sources include broccoli, nuts, olive and soybean oil^[22], as well as edible algae.
• Vitamin K2 differs in structure from K1 and is also called menaquinone. Menaquinones are created from vitamin K1 due to the action of bacteria. They contain an extra fatty acid side chain and are divided according to their side chain length. The most important forms of vitamin K2 include MK4 and MK7. Biologically, longer-length molecules, such as MK7, are more easily absorbable with greater effects than shorter MK molecules^[23] and are available as part of supplements in smaller quantities. Small amounts of vitamin K2 feature in fermented products, such as natto and cheese, butter, eggs and meat.

Absorption and Bioavailability. Most of the vitamin K we consume is in the form of K1. K2 is mainly produced by gut bacteria in small quantities from the conversion of K1. Gut bacteria are also required for its absorption, alongside healthy bile acids. The liver has been shown to store vitamin K1, while vitamin K2 can be found in higher concentrations in all other body tissues. Vitamin K derived from oils and supplements is better absorbed (up to 80%) by comparison to that found in leafy vegetables (4-17%). Pairing green leafy vegetables with fats in a meal modestly increases the absorption of vitamin K.

Vitamin K Supplementation

Vitamin K supplementation is usually only prescribed to treat deficiency (which induces acquired hypoprothrombinemia) or severe side effects of vitamin K antagonists, such as warfarin (usually in the context of overdose). Patients on warfarin are often recommended a diet plan that emphasizes a higher intake of Vitamin K-rich foods to combat the side effects.

Supplementation is currently being studied for treating other health conditions, including coronary heart disease, osteoporosis, osteoarthritis, kidney stones and cancer. While research is inconclusive, the adverse effects associated with supplementing vitamin K are rare. Better results are generally observed when longer chain forms of Vitamin K2 are taken orally alongside other nutrients.

Contraindications and Side Effects

Contraindications. Supplementation is contraindicated in cases of genetic hypoprothrombinemia (not acquired), severe kidney disease or failure, heparin overuse, or vitamin K hypersensitivity.^[24]

The carboxylation of both coagulant and anticoagulant components depends on vitamin K. Very high supplemental intake is potentially associated with increased blood clotting factors such as prothrombin and should be avoided by those at risk for blood clotting disorders. Despite this, patients on warfarin are advised to consume a diet high in vitamin K to offset the side effects of warfarin, which disrupts the action of vitamin K.

Adverse Reactions in response to oral vitamin K1 or K2 are exceedingly rare. Few people are known to be allergic or hypersensitive to Vitamin K1, yet the reported reactions are typically mild unless the vitamin is administered by IV. Vitamin K2 does not appear to pose any side effects when healthy individuals take it orally, even at higher than recommended doses. One study has confirmed that it does not increase blood coagulation factors in healthy individuals^[25].

Synthetic Vitamin K, known as Vitamin K3 or menadione, is toxic to humans and animals. It is currently banned in the US and ought to be avoided.

Conclusion

Vitamin K is a highly underestimated nutrient that is abundant in some of the healthiest food sources. Emphasizing vitamin K intake is known to improve many aspects of one’s health across the lifespan. Aside from activating crucial proteins required for everyday living, increasing one’s intake of vitamin K helps to emphasize the core components of a nutritionally complete diet. Vitamin K is best known for its ability to regulate coagulation, its positive effects on bone health, and the way it helps lower tissue calcification. Current research suggests that it may additionally serve to lower the risk for other lifestyle diseases.

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