Vitamin K1

Vitamin K is a significant but often underappreciated nutrient. Essential for various bodily functions, Vitamin K's role extends beyond its well-known contribution to blood clotting. 

Vitamin K, existing in two primary forms – K1 (phylloquinone) and K2 (menaquinones) – plays a pivotal role in health. 

Phylloquinone, predominantly found in green leafy vegetables, is best known for its crucial role in blood coagulation, a process vital for preventing excessive bleeding. However, the scope of Vitamin K1 extends beyond blood clotting, influencing other aspects of health, including bone metabolism.

This article explores the functions of vitamin K1 more specifically as a biomarker by delving into its functions, dietary sources, and daily requirements, and discussing the significance of lab testing for Vitamin K and related biomarkers.

Understanding Vitamin K1

Vitamin K1, known scientifically as phylloquinone, is an essential nutrient with specific roles in human health.

Definition of Vitamin K1: What is Vitamin K1?  [8.]

Vitamin K1, also known as phylloquinone, is a fat-soluble vitamin primarily found in green leafy vegetables and certain plant oils. Structurally, vitamin K1 contains a methylated ring with an attached phytyl side chain. 

Unlike vitamin K2, which is synthesized by bacteria and found in animal products and fermented foods, vitamin K1 is exclusively derived from plant-based sources in the diet. After ingestion, vitamin K1 is absorbed in the small intestine along with dietary fat and incorporated into chylomicrons for transport to the liver, where it is converted to vitamin K2. 

This conversion involves the removal of the phytyl side chain, resulting in the formation of menaquinone-4 (MK-4), the primary form of vitamin K2 found in the liver. 

The liver also stores vitamin K1, releasing it into circulation as needed for various biological functions, including blood clotting and bone metabolism.

Functions of Vitamin K1 in the Body: What Does Vitamin K1 Do?

Vitamin K1’s primary function lies in blood clotting: Vitamin K1 is essential for synthesizing certain blood clotting factors.  Without adequate Vitamin K1, the body cannot produce these clotting factors effectively.

Otherwise, vitamin K1 primarily functions as a precursor to vitamin K2, which is the biologically active form involved in various physiological processes. Upon ingestion, vitamin K1 is absorbed in the small intestine and transported to the liver, where it is converted into vitamin K2, particularly menaquinone-4 (MK-4).  [8.]

Dietary Sources of Vitamin K1

Dietary Vitamin K1 comes from plant-based sources:

Green leafy vegetables:

• Kale
• Spinach
• Swiss chard
• Collard greens
• Turnip greens
• Mustard greens
• Beet greens
• Romaine lettuce
• Broccoli
• Brussels sprouts

Other vegetables:

• Cabbage
• Asparagus
• Green peas
• Green beans
• Celery
• Leeks
• Cucumbers

Herbs and spices:

• Parsley
• Thyme
• Basil
• Sage
• Dill
• Oregano
• Cilantro
• Chives
• Marjoram

Vitamin K Deficiency  [3.]

While Vitamin K deficiency is rare in adults, it can lead to increased bleeding time due to impaired blood clotting. Newborns are at a higher risk of Vitamin K deficiency, which is typically prevented through supplementation at birth.

Recommended Vitamin K Intake and Supplementation

RDA of Vitamin K: How Much K1 Should I Get Per Day?  [9.]

The Recommended Dietary Allowance (RDA) for vitamin K varies based on age and gender.  There is no recommendation regarding vitamin K1 vs K2 intake. 

For adult men, the RDA is 120 micrograms (mcg) of vitamin K per day.  For adult women, the RDA is 90 mcg per day.  The RDA does not change in pregnancy or lactation. 

Indications for Vitamin K Supplementation  [3., 6., 8.]

Vitamin K Deficiency

Although rare, Vitamin K deficiency can lead to serious health issues.  Symptoms of deficiency can include easy bruising, excessive bleeding from wounds or punctures, and heavy menstrual bleeding in women.

Populations at increased risk of vitamin K deficiency include newborns, individuals with certain digestive disorders affecting nutrient absorption, and those on long-term antibiotics are more susceptible to Vitamin K deficiency.

Blood Clotting Disorders

Vitamin K is crucial for synthesizing clotting factors, which are proteins necessary for blood coagulation.

Bone Health

Vitamin K plays a key role in bone metabolism by aiding in the carboxylation of certain bone proteins; this contributes to bone formation and maintenance and reduces the risk of osteoporosis.

Cardiovascular Health

This benefit is particularly associated with Vitamin K2, which helps prevent the calcification of arteries and other soft tissues.

Prevention and Treatment of Bleeding Disorders

Adequate Vitamin K levels are essential for normal blood clotting, preventing conditions like hemorrhagic disease, particularly in newborns.

Balancing Vitamin K1 Intake with Anticoagulant Therapies

Particularly for individuals on anticoagulant medications like warfarin, balancing Vitamin K1 intake is important to avoid interfering with the medication's effectiveness. Consistent dietary intake of Vitamin K1 helps in managing its levels.

Individuals on anticoagulant medications should speak with their healthcare provider regarding an appropriate intake of vitamin K, particularly vitamin K1 from vegetables.  

Lab Testing for Vitamin K1

Measuring Vitamin K1 levels in the body requires testing vitamin K levels, generally.  Alternatively, assessing clotting function may be appropriate.  

Methods of Vitamin K Testing

Vitamin K levels are usually measured through blood tests in serum and plasma. [8.]

However, direct measurement of Vitamin K in the blood is controversial.  [1., 2.]

Instead, some experts recommend indirect testing that assess blood clotting:

Prothrombin Time (PT) Test and PTT Test: these tests measure how long it takes for blood to clot. Since Vitamin K is vital for clotting, prolonged clotting time can suggest a deficiency.

Some experts note that urinary metabolites of vitamin K may be an alternative method of testing.  [1.]

Interpreting Vitamin K Test Results

Reference ranges can vary depending on the lab used; therefore it is important to contact the laboratory used to determine reference ranges.  

Reference ranges for vitamin K testing in the serum are often given as 0.2-3.2 ng/mL, although  impaired blood clotting has been associated with levels below 0.5 ng/mL.  [10.]

Factors Influencing Vitamin K Levels

Several factors can affect Vitamin K levels and/or function in the body:

Dietary Intake: the amount and type of Vitamin K-rich foods consumed significantly influence blood levels.

Gut Health: conditions affecting gut health, such as celiac disease or Crohn’s disease, can impair Vitamin K absorption.

Medications: certain medications like antibiotics and anticoagulants, can affect Vitamin K metabolism.  Specifically, broad-spectrum antibiotics can deplete the bacteria that produce vitamin K, while cephalosporins can inhibit vitamin K function.  [6.]  Anticoagulants impair vitamin K function.  

The Clinical Importance of Vitamin K Testing

Regular testing of Vitamin K levels is important in certain situations:

Identifying Deficiencies: early detection of low Vitamin K levels is crucial, especially in populations at risk, like newborns and individuals with malabsorption disorders.

Guiding Treatment: in cases of bleeding disorders or osteoporosis, Vitamin K testing can inform treatment strategies.

Monitoring for Medication Interactions: for individuals on anticoagulant therapy, monitoring Vitamin K levels may be important.

Related Biomarkers and Their Testing

To fully understand the function of Vitamin K in the body, considering related biomarkers may provide insight.

Biomarkers Associated with Vitamin K

The effectiveness and activity of Vitamin K in the body are closely related to several other health markers:

• Vitamin D: vitamin D and Vitamin K work synergistically in bone health and calcium metabolism, making it important to assess Vitamin D levels when assessing bone health.

• Prothrombin time test with an INR (PT/INR): the prothrombin time test with an international normalized ratio (PT/INR) is a laboratory test used to assess the blood's ability to clot by measuring the time it takes for blood to clot, normalized to a standard scale, to monitor and evaluate coagulation status and the effectiveness of anticoagulant therapy.  PT monitors the extrinsic clotting pathway.  

• Partial Thromboplastin time (PTT): the partial thromboplastin time (PTT) test is a laboratory assay used to evaluate the intrinsic pathway of coagulation, measuring the time it takes for blood to clot when specific reagents are added. It is often employed to assess the function of factors involved in the clotting cascade and to monitor patients on heparin therapy.

Diet and Lifestyle Measures to Optimize Vitamin K Levels and Function

• Incorporate vitamin K-rich foods into your diet, such as leafy greens (e.g., kale, spinach, Swiss chard), broccoli, Brussels sprouts, and parsley.  [9.]  Individuals on anticoagulant medications should speak to their doctor before adjusting their dietary intake of these vegetables. 

• Consume fermented foods like natto, sauerkraut, and kefir, which contain vitamin K2-producing bacteria.  [9.]

• Include healthy fats in your diet, as vitamin K is fat-soluble and requires dietary fats for absorption. Examples include olive oil, avocado, nuts, and seeds.

• Avoid excessive alcohol consumption, as it may impair vitamin K absorption and utilization.  [5.]

• Engage in regular physical activity, which supports overall metabolic health and may indirectly enhance vitamin K function.

• Practice stress management techniques, as chronic stress can negatively impact nutrient absorption and utilization and affect vitamin K-dependent proteins and is associated with increased oxidative stress and depression.  [11.]

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