Vitamin K1: Benefits, Food Sources, Dosage & Deficiency Guide

Vitamin K1, also known as phylloquinone, is an essential fat-soluble vitamin that plays a crucial role in blood clotting and overall health. Found predominantly in leafy green vegetables, this vital nutrient supports various bodily functions and may offer protective benefits beyond its primary role in coagulation.

While many people are familiar with vitamins A, C, and D, vitamin K often receives less attention despite its critical importance. Understanding vitamin K1, its functions, sources, and recommended intake can help you optimize your nutritional status and support long-term health.

What Is Vitamin K1?

Vitamin K1, or phylloquinone, is one of two primary forms of vitamin K found in the human diet. The “K” designation comes from the German word “Koagulation,” reflecting its essential role in blood clotting processes.

As a fat-soluble vitamin, K1 is absorbed best when consumed with dietary fats. It’s synthesized by plants during photosynthesis, which explains why green vegetables are such excellent sources. Once absorbed, vitamin K1 is transported to the liver where it supports the production of clotting factors.

Unlike vitamin K2, which is found in fermented foods and animal products, vitamin K1 comes primarily from plant sources and represents about 75-90% of total vitamin K intake in Western diets.

Health Benefits of Vitamin K1

Blood Clotting Support

The primary and most well-established function of vitamin K1 is its role in blood coagulation. This vitamin is necessary for producing several proteins called clotting factors, which work together to form blood clots when you experience cuts or injuries.

Without adequate vitamin K1, your blood cannot clot properly, leading to excessive bleeding from even minor wounds. This clotting mechanism is essential for wound healing and preventing dangerous blood loss in both everyday situations and more serious injuries.

Bone Health

Research suggests that vitamin K1 may contribute to bone health by supporting bone mineralization and reducing fracture risk. This vitamin activates osteocalcin, a protein that binds calcium to bone tissue, helping to build and maintain strong bones.

Several observational studies have found associations between higher vitamin K intake and improved bone mineral density, particularly in postmenopausal women. Some research indicates that adequate vitamin K1 consumption may reduce the risk of hip fractures in older adults.

However, the relationship between vitamin K1 and bone health requires further investigation, as study results have been mixed.

Cardiovascular Health

Vitamin K1 may help protect against arterial calcification, a process where calcium deposits accumulate in blood vessel walls, making them stiff and less flexible. This hardening of the arteries is a risk factor for cardiovascular disease.

Vitamin K1 activates matrix Gla protein (MGP), which inhibits calcium deposits in blood vessels and soft tissues. By preventing arterial calcification, vitamin K1 may support overall heart health and reduce cardiovascular disease risk.

While preliminary research is promising, more extensive clinical trials are needed to fully understand vitamin K1’s role in heart disease prevention.

Recommended Daily Intake of Vitamin K1

The adequate intake (AI) levels for vitamin K, which includes K1, vary by age and gender. These recommendations are based on the amount needed to maintain proper blood clotting:

• Infants 0-6 months: 2 micrograms (mcg) per day
• Infants 7-12 months: 2.5 mcg per day
• Children 1-3 years: 30 mcg per day
• Children 4-8 years: 55 mcg per day
• Children 9-13 years: 60 mcg per day
• Adolescents 14-18 years: 75 mcg per day
• Adult men 19+ years: 120 mcg per day
• Adult women 19+ years: 90 mcg per day
• Pregnant and lactating women: 90 mcg per day

Most healthy individuals can meet these requirements through a balanced diet rich in vegetables, particularly leafy greens. Unlike some vitamins, there is no established upper limit for vitamin K1 intake, as toxicity is extremely rare.

Best Food Sources of Vitamin K1

Vitamin K1 is abundant in green vegetables, especially leafy varieties. The deeper the green color, the higher the vitamin K1 content tends to be. Here are the top food sources:

Leafy Green Vegetables

• Kale (cooked): 1,062 mcg per cup – provides over 1,000% of the daily value
• Collard greens (cooked): 836 mcg per cup
• Spinach (cooked): 888 mcg per cup
• Turnip greens (cooked): 529 mcg per cup
• Swiss chard (raw): 299 mcg per cup
• Mustard greens (cooked): 419 mcg per cup
• Dandelion greens (raw): 428 mcg per cup
• Arugula (raw): 108 mcg per cup

Other Vegetables

• Broccoli (cooked): 220 mcg per cup
• Brussels sprouts (cooked): 218 mcg per cup
• Cabbage (cooked): 163 mcg per cup
• Asparagus (cooked): 91 mcg per cup
• Green beans: 60 mcg per cup

Herbs and Seasonings

• Dried basil: 108 mcg per tablespoon
• Fresh parsley: 82 mcg per 1/4 cup
• Dried thyme: 71 mcg per tablespoon
• Dried oregano: 60 mcg per tablespoon

Other Sources

• Soybean oil: 25 mcg per tablespoon
• Canola oil: 10 mcg per tablespoon
• Edamame: 21 mcg per 1/2 cup
• Kiwi fruit: 28 mcg per medium fruit
• Avocado: 21 mcg per half fruit

Tips for Maximizing Absorption

Since vitamin K1 is fat-soluble, consuming it with dietary fat enhances absorption. Consider these strategies:

• Add olive oil or avocado to salads containing leafy greens
• Cook greens in a small amount of healthy fat
• Include nuts or seeds with vitamin K-rich vegetables
• Use oil-based salad dressings rather than fat-free versions

Vitamin K1 Deficiency: Signs and Symptoms

Vitamin K1 deficiency is relatively uncommon in healthy adults due to its widespread availability in foods and its recycling by the body. However, certain populations are at higher risk.

Who Is at Risk?

• Newborns: Infants are born with low vitamin K stores and receive limited amounts through breast milk
• People with malabsorption disorders: Conditions like celiac disease, Crohn’s disease, and ulcerative colitis can impair fat absorption
• Those with liver disease: The liver plays a key role in vitamin K metabolism
• Individuals taking certain medications: Some antibiotics and medications that affect fat absorption may reduce vitamin K levels
• People with very limited diets: Those who don’t consume vegetables regularly

Deficiency Symptoms

The primary symptom of vitamin K1 deficiency is impaired blood clotting, which can manifest as:

• Easy bruising
• Excessive bleeding from wounds or cuts
• Heavy menstrual periods
• Blood in urine or stool
• Bleeding gums
• Nosebleeds

If you experience any of these symptoms, consult your healthcare provider. A simple blood test can determine your vitamin K status and clotting ability.

Can You Get Too Much Vitamin K1?

Unlike some vitamins, vitamin K1 has no established upper intake level because toxicity from dietary sources is extremely rare. The body regulates vitamin K1 absorption efficiently, and excess amounts are typically excreted.

Eating large amounts of vitamin K1-rich foods, such as leafy greens, is generally safe. You’re more likely to experience digestive discomfort from excessive fiber intake than any adverse effects from vitamin K1 itself.

Special Considerations

However, certain individuals need to monitor their vitamin K1 intake carefully:

People taking blood-thinning medications: If you’re on anticoagulant therapy, maintaining consistent vitamin K1 intake is important. Sudden increases or decreases can affect medication effectiveness. Consult your healthcare provider or dietitian about appropriate vitamin K1 intake for your situation.

Individuals with specific health conditions: Those with kidney disease on dialysis, liver disease, or gallbladder problems should discuss vitamin K1 supplementation with their doctor before taking additional amounts beyond diet.

Vitamin K1 Supplements: When Are They Necessary?

Most people can meet their vitamin K1 needs through diet alone. Supplements are typically unnecessary unless you have a diagnosed deficiency or a condition that impairs vitamin K absorption.

Forms of Supplementation

Vitamin K1 supplements are available as:

• Standalone supplements
• Part of multivitamin formulas
• Combined with other vitamins like calcium and vitamin D in bone health formulas

When to Consider Supplements

Your healthcare provider might recommend vitamin K1 supplements if you:

• Have been diagnosed with a vitamin K deficiency
• Have a malabsorption disorder
• Take medications that interfere with vitamin K absorption
• Have liver disease affecting vitamin K metabolism
• Cannot consume adequate amounts through diet

Always consult with a healthcare professional before starting any supplement regimen, as they can assess your individual needs and determine appropriate dosing.

Interactions with Medications

Vitamin K1 can interact with several types of medications. It’s important to discuss your vitamin K intake with your healthcare provider if you take any of the following:

Blood-Thinning Medications

Anticoagulant medications work by interfering with vitamin K-dependent clotting factors. Consuming high amounts of vitamin K1 can reduce the effectiveness of these medications. Consistency in vitamin K intake is key for people on anticoagulant therapy.

Antibiotics

Some broad-spectrum antibiotics can reduce vitamin K-producing bacteria in the intestines, potentially lowering vitamin K levels over time with prolonged use.

Weight Loss Medications

Medications that reduce fat absorption can also impair the absorption of fat-soluble vitamins like vitamin K1.

Other Medications

Certain medications for seizures, high cholesterol, and cancer treatment may affect vitamin K metabolism. Discuss your vitamin K intake with your healthcare provider if you take any long-term medications.

Vitamin K1 vs. Vitamin K2: What’s the Difference?

While both vitamin K1 and K2 belong to the vitamin K family, they have different sources and some distinct functions:

Sources

• Vitamin K1: Found primarily in green vegetables and plant oils
• Vitamin K2: Found in fermented foods, animal products, and produced by gut bacteria

Functions

• Vitamin K1: Primarily involved in blood clotting; transported mainly to the liver
• Vitamin K2: More involved in calcium metabolism; better distributed to bones and blood vessels

Absorption and Retention

Vitamin K2 appears to remain in the body longer and may be more bioavailable than K1. Some research suggests K2 may be more effective for bone and cardiovascular health, though both forms provide important benefits.

Most people consume much more K1 than K2 in their diet, and both forms contribute to overall vitamin K status.

Frequently Asked Questions

How do I know if I need more vitamin K1?

Most healthy individuals consuming a varied diet with vegetables get adequate vitamin K1. Signs you might need more include easy bruising, excessive bleeding, or if you have conditions affecting fat absorption. A blood test can assess your clotting ability and vitamin K status.

Can cooking destroy vitamin K1?

Vitamin K1 is relatively heat-stable, so cooking generally doesn’t significantly reduce its content. In fact, cooked greens often contain more vitamin K1 per serving than raw greens because cooking reduces their volume, concentrating nutrients.

Is it better to take vitamin K1 in the morning or evening?

If you take a vitamin K1 supplement, taking it with a meal containing some fat optimizes absorption. The time of day is less important than consistency, especially if you take medications that interact with vitamin K.

Do I need vitamin K1 supplements if I eat a lot of vegetables?

Probably not. If you regularly consume leafy greens and other vitamin K-rich foods, you’re likely meeting your needs through diet alone. Supplements are typically only necessary for people with specific deficiencies or medical conditions.

Can vitamin K1 help with dark circles under eyes?

Some topical skincare products contain vitamin K and claim to reduce dark circles. While vitamin K may help with bruising and blood vessel issues, scientific evidence supporting its effectiveness for under-eye circles is limited.

Is vitamin K1 safe during pregnancy?

Vitamin K1 from food sources is safe and important during pregnancy. However, high-dose supplements should only be taken under medical supervision. The recommended adequate intake for pregnant women is 90 mcg per day, the same as for non-pregnant adult women.

Tips for Increasing Vitamin K1 Intake

If you want to boost your vitamin K1 consumption naturally, try these strategies:

• Start your day with a green smoothie containing spinach or kale
• Add leafy greens to soups and stews for an easy nutrient boost
• Make salads the main course with a variety of dark leafy greens
• Snack on edamame for a vitamin K-rich protein source
• Use fresh herbs generously in cooking for flavor and nutrients
• Try new greens like dandelion greens, arugula, or Swiss chard
• Add vegetables to breakfast through omelets or breakfast scrambles
• Choose vegetable-based side dishes like sautéed spinach or roasted Brussels sprouts

The Bottom Line

Vitamin K1 is an essential nutrient that plays a critical role in blood clotting and may support bone and cardiovascular health. While deficiency is uncommon in healthy adults, ensuring adequate intake through a diet rich in leafy green vegetables is important for optimal health.

Most people can easily meet their vitamin K1 needs by including plenty of dark green vegetables in their daily meals. A single serving of cooked kale, spinach, or collard greens provides more than the entire daily requirement.

If you have concerns about your vitamin K1 status, take medications that interact with vitamin K, or have conditions affecting nutrient absorption, consult your healthcare provider. They can assess your individual needs and determine whether dietary changes or supplementation might be beneficial.

By understanding the importance of vitamin K1 and incorporating vitamin K-rich foods into your diet, you can support healthy blood clotting and potentially benefit your bones and heart as well.

Sources:

• National Institutes of Health – Office of Dietary Supplements: Vitamin K Fact Sheet
• National Center for Biotechnology Information: Vitamin K and Bone Health
• National Center for Biotechnology Information: Vitamin K and Cardiovascular Health
• USDA FoodData Central: Vitamin K Content in Foods
• National Center for Biotechnology Information: Vitamin K Metabolism and Function