Vitamin K is a vital fat-soluble nutrient essential for blood clotting and bone health, with vitamin K1 (phylloquinone) found abundantly in green leafy vegetables forming the primary dietary source in the UK. Whilst deficiency is uncommon in healthy adults eating a balanced diet, certain groups—including those with malabsorption disorders or taking warfarin—require careful attention to intake. Understanding which vegetables provide the highest amounts of vitamin K and how to incorporate them effectively into your diet supports optimal health outcomes. This article explores vitamin K-rich vegetable sources, daily requirements, and practical dietary strategies aligned with UK guidance.

What Is Vitamin K and Why Do You Need It?

Vitamin K is a fat-soluble vitamin essential for several critical physiological processes in the human body. It exists primarily in two naturally occurring forms: vitamin K1 (phylloquinone), found predominantly in green leafy vegetables, and vitamin K2 (menaquinone), present in fermented foods and animal products. While bacteria in the gut can produce some vitamin K2, its contribution to overall vitamin K status is uncertain, with dietary vitamin K1 being the main source in the UK.

The primary function of vitamin K is its role in blood clotting (coagulation). It acts as a cofactor for enzymes that synthesise clotting factors in the liver, including factors II, VII, IX, and X, as well as proteins C and S. Without adequate vitamin K, the blood cannot clot properly, leading to increased bleeding risk and potentially serious haemorrhagic complications. This is why newborn babies in the UK routinely receive vitamin K supplementation at birth (typically as an intramuscular injection), as they have low stores and limited ability to produce it.

Beyond coagulation, vitamin K contributes to bone health by activating proteins that regulate calcium deposition in bones and teeth. Osteocalcin, a vitamin K-dependent protein, helps bind calcium to the bone matrix, supporting bone mineralisation and strength. Research has also found associations between vitamin K and cardiovascular health, with observational studies suggesting links to reduced vascular calcification, though evidence is insufficient for NICE to recommend supplementation for cardiovascular outcomes.

Deficiency is relatively uncommon in healthy adults consuming a balanced diet, but certain groups face higher risk, including individuals with malabsorption disorders (such as coeliac disease, Crohn's disease, or cholestatic liver disease), those taking long-term antibiotics that disrupt gut bacteria, and people using medications that affect fat absorption (such as orlistat or bile acid sequestrants). People taking warfarin need to maintain consistent vitamin K intake rather than avoiding it, as warfarin works by antagonising vitamin K activity in the clotting cascade.

Vegetables High in Vitamin K: UK Food Sources

Green leafy vegetables represent the richest dietary sources of vitamin K1, making them cornerstone foods for meeting daily requirements. Kale stands out as exceptionally high in vitamin K, with a single 100g serving of cooked kale providing approximately 817 micrograms—far exceeding daily needs. Similarly, spinach offers around 483 micrograms per 100g when cooked, whilst raw spinach contains approximately 400-500 micrograms per 100g serving.

Spring greens, cabbage, and Brussels sprouts are excellent UK-grown options widely available throughout the year. Spring greens provide roughly 340 micrograms per 100g cooked portion, whilst Brussels sprouts (boiled) contain approximately 177 micrograms per 100g. These brassica vegetables not only deliver substantial vitamin K but also provide fibre, vitamin C, and other beneficial phytonutrients.

Other valuable vegetable sources include:

• Broccoli (boiled) – approximately 141 micrograms per 100g

• Asparagus (cooked) – around 60 micrograms per 100g

• Green beans (cooked) – approximately 48 micrograms per 100g

• Peas (cooked) – roughly 26 micrograms per 100g

• Lettuce varieties (particularly darker leaves like romaine) – 24–126 micrograms per 100g

It's worth noting that cooking methods and fat content influence vitamin K absorption. As a fat-soluble vitamin, vitamin K is better absorbed when consumed with dietary fats. Lightly cooking vegetables can increase bioavailability by breaking down cell walls, though excessive boiling may leach some nutrients into cooking water. Adding a small amount of olive oil, butter, or consuming vegetables alongside other fat-containing foods enhances absorption.

Herbs also contribute significantly—parsley contains approximately 548 micrograms per 100g, though typical serving sizes are much smaller. Even modest amounts of these vitamin K-rich vegetables can substantially contribute to daily intake. Note that vitamin K content can vary between fresh and frozen produce, and by growing conditions, variety, and preparation methods.

How Much Vitamin K Do You Need Daily?

The UK Department of Health provides guidance on adequate vitamin K intake, though unlike some nutrients, there is no established Reference Nutrient Intake (RNI) due to limited data on requirements. Instead, safe intake levels have been determined based on observed intakes in healthy populations and the amounts needed to maintain normal blood clotting.

For all age groups, the suggested adequate intake is approximately 1 microgram per kilogram of body weight per day. For an average adult, this typically equates to around 65-80 micrograms daily, though individual needs vary with body weight. Children's requirements similarly scale with body weight, rather than having fixed targets.

Pregnant and breastfeeding women do not require significantly increased amounts, as vitamin K does not readily cross the placenta and breast milk contains relatively low concentrations—hence the importance of newborn supplementation.

The NHS emphasises that most people in the UK obtain sufficient vitamin K through a varied diet including vegetables, and deficiency is uncommon in healthy individuals. No upper intake level has been established in the UK, and supplements are usually unnecessary with a balanced diet unless specifically advised by a healthcare professional.

Special considerations apply to certain groups. Individuals taking warfarin must maintain consistent vitamin K intake rather than avoiding it entirely. Sudden increases or decreases in dietary vitamin K can affect anticoagulation control and International Normalised Ratio (INR) values. These patients should consult their GP or anticoagulation clinic before making significant dietary changes or starting/stopping vitamin K supplements. Note that direct oral anticoagulants (DOACs) are not affected by vitamin K intake.

People with fat malabsorption conditions (including cystic fibrosis, coeliac disease, inflammatory bowel disease, cholestatic liver disease, or following bariatric surgery) may require monitoring and potentially supplementation, as vitamin K absorption depends on adequate fat digestion and bile acid function. Long-term broad-spectrum antibiotic use can also reduce vitamin K production by gut bacteria, and when combined with poor dietary intake or other risk factors, may lead to deficiency in some individuals.

Tips for Including Vitamin K Vegetables in Your Diet

Incorporating vitamin K-rich vegetables into your daily diet is straightforward and supports overall nutritional balance. Aim to include green leafy vegetables regularly as part of your five-a-day—this typically provides sufficient vitamin K for most people. A simple side salad with mixed leaves, a portion of steamed broccoli with dinner, or adding spinach to morning eggs can easily meet requirements. If you're taking warfarin, keep your intake consistent and inform your anticoagulation clinic about your typical diet.

Practical preparation methods that preserve and enhance vitamin K include:

• Light steaming or sautéing rather than prolonged boiling, which minimises nutrient loss into cooking water

• Adding healthy fats such as olive oil, rapeseed oil, or a knob of butter when cooking or dressing vegetables to improve absorption

• Incorporating raw vegetables into salads, smoothies, or as crudités—whilst cooking can increase bioavailability, raw vegetables retain most of their vitamin K content

• Batch cooking and freezing greens like spinach or kale for convenient additions to soups, stews, and pasta dishes

Menu ideas for boosting vitamin K intake include adding kale or spinach to smoothies (the fruit masks any bitter taste), stirring spring greens into curries or stir-fries, roasting Brussels sprouts with garlic and olive oil, or making vegetable-rich soups with broccoli or cabbage as base ingredients.

For those on anticoagulant therapy, consistency is key. Rather than avoiding vitamin K vegetables, establish a regular pattern of consumption and inform your anticoagulation clinic of your typical diet. This allows appropriate dose adjustment whilst maintaining the cardiovascular and bone health benefits these vegetables provide.

When to seek advice: If you experience unusual bruising, prolonged bleeding from minor cuts, or notice blood in urine or stools, contact your GP, as these may indicate clotting abnormalities. Seek immediate medical help for heavy bleeding that does not stop, black tarry stools, coughing up blood, or sudden severe headache with neurological symptoms. Individuals with diagnosed malabsorption conditions should discuss vitamin K status with their healthcare provider, particularly if experiencing bone health concerns or taking medications affecting fat absorption.

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