Compared to other fat-soluble vitamins, very small amounts of vitamin K circulate in the blood, but this doesn't mean vitamin K plays a small role in human health. From blood clotting to bone health, vitamin K deficiency has far-reaching implications, and up to 31% of healthy individuals are vitamin K-deficient. This article explores the causes, symptoms, and integrative insights for managing vitamin K deficiency.
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What Is Vitamin K?
Vitamin K is a fat-soluble vitamin primarily known for its role in blood clotting.
Types of Vitamin K
Vitamin K exists in two primary forms: vitamin K1 (phylloquinone) and vitamin K2 (menaquinone).
Vitamin K1 (Phylloquinone)
Vitamin K1 is exclusively derived from plant sources, such as leafy green and cruciferous vegetables. It is involved in blood clotting and can be converted into vitamin K2 in animals.
Vitamin K2 (Menaquinone)
Vitamin K2 comprises a range of vitamin K forms collectively called menaquinones. Menaquinones are synthesized by the commensal bacteria in the human intestinal microbiome and are naturally found in fermented foods and animal products.
The different forms of vitamin K2 differ structurally by the number of 5-carbon units in their side chains. These forms are named based on the number of 5-carbon units, designated as MK-n (where 'n' ranges from 2 to 13 and denotes the length of the side chain). Examples include MK4 and MK7.
Whereas vitamin K1 is primarily involved in blood clotting, vitamin K2 is more closely involved in maintaining bone and cardiovascular health.
Biological Functions of Vitamin K
Vitamin K is a cofactor for the carboxylation of glutamic acid residues in vitamin K-dependent proteins, enabling their activation for blood clotting, bone health, vascular protection, and other cellular processes. This biochemical reaction refers to a process where a small carboxyl group is added to proteins to allow them to bind to calcium, which is required for them to perform their jobs properly:
- Blood Clotting: Vitamin K-dependent blood clotting factors II, VII, IX, and X act within the blood clotting cascade, a series of steps that allow the body to form a blood clot and stop bleeding.
- Bone Building: Osteocalcin is a protein secreted by osteoblasts (bone-forming cells) that facilitates the incorporation of calcium into the bone matrix to maintain bone density and strength.
- Prevention of Arterial Calcification: Matrix Gla protein (MGP) inhibits calcium deposition in the arterial walls. This helps ensure calcium is deposited in bones rather than blood vessels, where it could lead to atherosclerosis and cardiovascular disease.
Causes of Vitamin K Deficiency
Vitamin K deficiency can result from several factors, from insufficient dietary intake to underlying medical conditions.
Dietary Insufficiency
Inadequate dietary intake can cause vitamin K deficiency. Individuals who consume a diet low in vitamin K-rich foods are at a higher risk of deficiency. Additionally, eating a low-fat diet can increase risk because vitamin K is best absorbed when eaten with fat.
Medical Conditions
Malabsorptive conditions that affect fat absorption can also lead to vitamin K deficiency. Disorders such as celiac disease, Crohn's disease, or cystic fibrosis can impair the body's ability to absorb fat-soluble vitamins. People with these conditions are more likely to develop deficiencies even if they eat adequate amounts of vitamin K-rich foods.
Medications
Long-term use of certain medications can interfere with the synthesis, absorption, and utilization of vitamin K, increasing the risk of deficiency:
- Warfarin and similar anticoagulants inhibit vitamin K activity
- Antibiotics, especially cephalosporins, can kill vitamin K-producing bacteria in the gut
- Bile acid sequestrants like cholestyramine and colestipol block intestinal absorption of bile acids and fat-soluble vitamins
- Orlistat is a weight-loss drug that reduces the absorption of dietary fat and, as a consequence, fat-soluble vitamins
Symptoms and Diagnosis
Vitamin K deficiency impairs blood clotting, causing hallmark symptoms like:
- Easy bruising
- Nosebleeds
- Bleeding gums
- Blood in urine and stools
- Heavy menstrual bleeding
In adults, vitamin K deficiency may not always cause significant bleeding unless it is severe or combined with other health conditions. Bleeding is more likely to occur in individuals with malabsorption syndromes, liver disease, or those taking medications that interfere with vitamin K metabolism.
In infants, vitamin K deficiency can cause life-threatening bleeding (hemorrhage) into the intestines or brain – a condition called vitamin K deficiency bleeding (VKDB).
Diagnostic Tests
Serum vitamin K levels are rarely measured to diagnose vitamin K deficiency. Instead, doctors will use blood clotting tests to determine if a deficiency exists:
A vitamin K deficiency will result in prolonged PT and elevated INR, indicating impaired blood clotting mechanisms and a longer-than-normal time for blood to clot.
If vitamin K administration subsequently normalizes PT, a prolonged PT is likely attributable to a vitamin K deficiency.
Because vitamin K is required for the carboxylation of osteocalcin in bone, vitamin K deficiency could also reduce bone mineralization and contribute to osteoporosis. Osteoporosis is diagnosed by dual-energy X-ray absorptiometry (DEXA) when a T-score below -2.5 indicates low bone mineral density.
Treatment and Management
Vitamin K deficiency can be corrected through various strategies that replenish vitamin K in the body.
Dietary Interventions
Increasing vitamin K intake through dietary changes is the first step in addressing a deficiency. Foods high in vitamin K include:
- Leafy green vegetables such as kale, spinach, and collard greens
- Cruciferous vegetables like broccoli and Brussels sprouts
- Meat, liver, dairy products, and egg yolks
- Fermented foods like natto and cheese
Per the Food and Nutrition Board guidelines, a daily vitamin K intake of at least 120 mcg for men and 90 mcg for women is necessary to prevent vitamin K deficiency in adults.
Dietary Supplements
Vitamin K is available in single- or multiple-nutrient supplements in varying doses and forms, including:
- Vitamin K1 as phylloquinone or phytonadione (synthetic K1)
- Vitamin K2 as MK-4 or MK-7
Vitamin K1 is the preferred form of vitamin K to correct deficiency. It is administered orally in doses up to 25 mg. The maximum effects of oral administration are observed around 24 hours after oral administration.
Medical Treatments
In more severe deficiency, especially when associated with significant bleeding, vitamin K1 can be administered via a subcutaneous or intramuscular injection. Vitamin K injections should correct the deficiency within 12-24 hours.
If vitamin K deficiency is caused by a medication, your doctor may recommend adjusting the medication or taking additional vitamin K supplements. Always consult your doctor before making any changes to your medication regimen, and never stop or alter the dose of your medication without your doctor's approval.
Integrative and Functional Approaches
Since vitamin K requires a healthy digestive system for proper absorption, addressing gut health can be helpful to optimize vitamin K levels and prevent deficiency. Examples may include:
- Treating preexisting malabsorptive gastrointestinal conditions
- Taking digestive enzymes with meals to facilitate fat digestion and absorption
- Taking gut-healing supplements, such as short-chain fatty acids, L-glutamine, and deglycyrrhizinated licorice
- Eating a plant-based diet rich in nutrients, such as fiber and polyphenols, has been associated with greater diversity and abundance of beneficial microbes in the gut microbiome
- Reinoculating the gut microbiome with probiotic and prebiotic supplements
Chronic stress can negatively affect gut health and nutrient absorption. Techniques like meditation, yoga, and deep breathing can help regulate the nervous system to support digestion and nutrient absorption through a mind-body approach to wellness.
In some cases, your healthcare provider may recommend taking supplemental vitamin K alongside other nutrients. For example, many supplements utilize nutrient synergy by combining vitamin K with vitamin D and/or calcium. Vitamin D enhances calcium absorption, while vitamin K helps ensure calcium is directed to the bones rather than accumulating in the arteries. Research supports the benefits of combined supplementation for promoting bone and cardiovascular health.
Given that vitamin K deficiency may be a risk factor for developing osteoporosis and coronary artery disease, partaking in aerobic and weight-bearing exercise can mitigate this risk and complement a whole-person treatment program:
- The American College of Sports Medicine suggests performing weight-bearing exercises 3-5 times per week, along with resistance training and activities that involve jumping 2-3 times per week. Each session should last 30-60 minutes and target all major muscle groups. Additionally, exercises that improve balance and posture, such as Tai Chi, are advised to help reduce the risk of falls and fractures.
- The American Heart Association recommends at least 150 minutes of moderate-intensity aerobic exercise per week and two or more muscle-strengthening sessions.
Special Considerations
Understanding how vitamin K affects infants and individuals with chronic diseases provides further insight into its importance across different life stages and health conditions.
Vitamin K Deficiency in Infants
Newborns have low vitamin K status due to:
- Limited transport of vitamin K across the placental barrier
- Low vitamin K storage in the liver
- Suboptimal function of vitamin K recycling mechanisms
- Immature gut microbiome
Additionally, exclusively breastfed infants are at further risk for vitamin K deficiency because breastmilk contains a relatively low amount of vitamin K.
The American Academy of Pediatrics recommends that all newborns receive a vitamin K injection shortly after birth to prevent VKDB. While some parents may be concerned about the safety of vitamin K injections, research has shown that the benefits far outweigh any potential risks. The injection is considered safe and is a standard practice in hospitals worldwide.
Vitamin K and Chronic Diseases
Research suggests that a higher intake of dietary vitamin K is nonlinearly and inversely associated with the risk of atherosclerotic cardiovascular disease, including ischemic heart disease, ischemic stroke, and peripheral artery disease. Vitamin K supplementation may reduce vascular calcification, but its ability to reverse atherosclerosis or significantly reduce cardiovascular risk requires further investigation through larger, long-term clinical trials.
Maintaining optimal vitamin K levels could potentially help individuals with diabetes manage their condition more effectively. Studies have demonstrated that higher circulating levels of vitamin K1 are associated with lower fasting glucose and insulin resistance, and that vitamin K2 supplementation significantly reduces fasting plasma gluocse levels in patients with type 2 diabetes.
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Key Takeaways
- Vitamin K is a fat-soluble vitamin important for blood clotting, bone health, and cardiovascular function.
- Vitamin D deficiency can lead to serious health complications, but proper dietary adjustments, supplements, and medical interventions can manage and correct this deficiency.
- By understanding the causes, symptoms, and treatment options for vitamin K deficiency, individuals can take proactive steps to prevent suboptimal vitamin K levels.
- If you suspect a vitamin K deficiency, consult a healthcare professional for a proper diagnosis and treatment plan.
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