Kale

Food · Vegetables · Leafy & Cruciferous

Connected to · 2

food source · 2

Vitamin K1
Raw kale has about 450–817 µg of vitamin K1 per 100 g, among the highest of any vegetable by weight. K1 does not dissolve in water and needs a little fat to be absorbed well.
Mechanism · 2
Mechanism · Fat-soluble, so it needs oil
K1 and the carotenoids do not dissolve in water; they have to ride in micelles formed with fat before they can reach the gut wall. A plate of boiled kale and a plate stir-fried with garlic and olive oil differ not in what they contain but in how much of it gets absorbed.
Safety · On warfarin, keep it steady
Raw kale leaves have about 450–817 µg of vitamin K1 per 100 g, while the adult adequate intake (AI) is about 90–120 µg a day; cooking changes the figure a little, and it stays high. K1 is needed to make clotting factors, the very step the blood thinner warfarin blocks, so people taking warfarin need not give up kale but should keep the amount they eat each day roughly steady.
Vitamin C
Raw kale has about 93–120 mg of vitamin C per 100 g, more than citrus fruit. Vitamin C is damaged by heat, so quick cooking with little water, or eating kale raw, keeps more of it.
Mechanism · 2
Mechanism · Two rules on one leaf
K1 needs fat, while vitamin C dissolves in water and is damaged by heat, so the same leaf follows two sets of rules. Quick cooking with little water and a little oil keeps a good share of both; eaten raw, kale keeps the most vitamin C.
Numbers · Vitamin C for very few calories
Raw kale has about 93–120 mg of vitamin C per 100 g, more than citrus fruit, at very few calories: about 35 kcal per 100 g, with about 2–3 g of fiber.

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What kale is

EVIDENCEGUIDE 1

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The most useful thing to know about kale is that it is very rich in vitamin K1, and the liver needs vitamin K to fit clotting factors with the parts that grab calcium. So people who take warfarin do not have to give it up, but they should keep the amount they eat each day roughly steady; a later chapter, on eating kale while taking warfarin, explains why.

Kale itself is a cabbage that refuses to form a head. Cabbage, broccoli, cauliflower, and kale are the same species; they differ only in where the plant puts its effort. Cabbage wraps its leaves into a ball, broccoli bunches its flower buds into one big head, and kale wraps nothing — every leaf opens outward.

Pigments such as chlorophyll and carotenoids build up only in light. The inner leaves of a cabbage sit in the dark, so they are pale and thin; every kale leaf gets sun, so the whole plant keeps storing pigment. That dark, dusky green is the thickness of that pigment.

Kale is also the vegetable the superfood wave lifted highest. Checked item by item, its vitamin K1, calcium, and carotenoids really do stand out; beyond those, it is simply a good ordinary vegetable.

Three dark curly kale leaves with ruffled margins and pale midribs. — A CLOSER LOOK
Open curly leaves reveal their veins
This is a curly variety; leaf colour helps explain pigment but cannot measure a vitamin K dose.

Educational content, not medical advice — consult a clinician.

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