Vitamin K1 in Plant-Based Foods

Dark leafy greens dominate vitamin K1 content. Parsley leads at ~1,640µg/100g, followed by kale (~817µg/100g), Swiss chard (~830µg/100g), spinach (~483µg/100g), collard greens (~437µg/100g), and broccoli (~102µg/100g). A single serving of kale or parsley easily provides the entire daily adequate intake. Leafy greens are unequivocally the richest plant source of vitamin K1 on the planet.

The Adequate Intake (AI) is 90µg/day for women and 120µg/day for men — there is no RDA for vitamin K1. A single cup of raw kale provides well over the AI. A handful of parsley (about 10g) delivers over 160µg. Plant-based eaters who include even modest amounts of leafy greens consistently meet or exceed the adequate intake with ease.

Vitamin K1 (phylloquinone) is found almost exclusively in green leafy vegetables and is the primary dietary form on plant-based diets. Vitamin K2 (menaquinone) is produced by bacteria in fermented foods like natto (fermented soybeans), tempeh, and sauerkraut — K2 content varies dramatically. The body can convert some dietary K1 to K2, though the efficiency is modest. For plant-based eaters, K1 from leafy greens is the reliable, consistent source.

Vitamin K1 has three major roles: (1) activating clotting factors essential for blood coagulation, (2) activating bone proteins (osteocalcin) that bind calcium and are critical for bone mineralisation, and (3) participating in calcium metabolism by directing calcium into bones and teeth rather than soft tissues and arteries. Vitamin K works synergistically with vitamin D and calcium — all three are necessary for robust bone health and cardiovascular safety.

Yes, absolutely. Plant-based diets are the richest dietary source of vitamin K1. Leafy greens — kale, spinach, collard greens, Swiss chard, parsley — are unequivocally the highest-concentration sources. A plant-based eater who includes even modest servings of cooked or raw leafy greens easily meets the adequate intake. This is one nutrient where plant-based diets have a decisive advantage over omnivorous diets.

Vitamin K activates osteocalcin, a bone matrix protein that binds calcium and stabilises the bone mineral lattice. Without adequate K1, osteocalcin remains inactive and cannot properly bind calcium, weakening bone. Vitamin K also works synergistically with vitamin D and calcium: vitamin D drives calcium absorption, vitamin K directs it into bone, and adequate calcium provides the substrate. All three together build and maintain bone density.

Vitamin K1 is fat-soluble, not water-soluble, so it is remarkably heat-stable. Boiling leafy greens causes minimal K1 loss — most is retained. In fact, cooking increases the bioavailability of vitamin K1 slightly by releasing it from plant cells. Cooking also reduces volume, making it easier to consume larger quantities of greens. Both raw and cooked greens deliver abundant vitamin K1; the best approach is to eat both forms regularly.

Vitamin K1 activates clotting factors, so it can reduce the effectiveness of anticoagulant medications like warfarin (Coumadin). Those taking warfarin should maintain consistent vitamin K1 intake — neither excessive nor negligible — and work with their physician. Sudden increases in vitamin K1 can reduce drug efficacy; sudden decreases can cause over-thinning. The key is consistency. Modern anticoagulants like DOACs (apixaban, rivaroxaban) are less affected by dietary vitamin K1.

Vitamin K activates proteins that regulate calcium deposition: osteocalcin directs calcium into bone, and matrix Gla protein (MGP) prevents calcification of soft tissues and arteries. Without adequate K1, calcium can deposit inappropriately in arteries while bone weakens. This is why vitamin K and calcium are synergistic — K1 ensures calcium goes where it belongs. For optimal bone and cardiovascular health, ensure adequate intake of both vitamins K1 and D alongside sufficient calcium.

Leafy greens are by far the dominant source, but some other vegetables contain meaningful amounts: broccoli (~102µg/100g), Brussels sprouts (~140µg/100g), cabbage (~76µg/100g), and green peas (~25µg/100g) all contribute. Herbs like parsley and dill are extraordinarily rich. However, volume-for-volume, dark leafy greens — particularly kale, spinach, chard, and collard greens — are incomparably the most practical, concentrated source for achieving adequate intake.

Overt vitamin K1 deficiency is rare in developed countries but manifests as impaired blood clotting and easy bruising. Subclinical deficiency — insufficient K1 to fully activate bone proteins — may contribute to weak bone and inappropriate vascular calcification. Marginal deficiency is more common in plant-based eaters who avoid green vegetables. The solution is simple: regular consumption of leafy greens. A handful of raw kale, a side of steamed collards, or some sautéed spinach provides weeks worth of adequate intake.

One cup (30g) of raw kale provides over 500µg, nearly six times the AI. A modest portion (100g) of cooked spinach delivers over 480µg. A few sprigs of parsley (5g) provides over 80µg. Green onions/scallions (207µg/100g) make an easy garnish. For convenience: add a handful of raw kale or spinach to smoothies, include leafy greens as a side at lunch or dinner, or add to soups and stir-fries. One simple daily habit — one serving of leafy greens — guarantees adequate K1 intake.