Kale Is Just a New Name for a Vegetable Europe Has Grown for Centuries

What trendy cafés list as "kale" has grown in Swiss gardens for centuries – under the name Federkohl. And raw, this local winter vegetable delivers more vitamin C per 100 grams than an orange. It is worth a closer look: not because of the superfood label, but because of what is actually in the leaves.

"Kale" and Federkohl are botanically the same vegetable

Behind the English trend word stands an old acquaintance: Brassica oleracea var. sabellica, known in Switzerland as Federkohl and elsewhere as kale, curly kale or winter cabbage. Like broccoli and cauliflower, it belongs to the brassica family and has been cultivated in Central Europe for generations. In northern Germany, the winter kale meal is a fixed social event.

In the 2010s, "kale" became a celebrated superfood, primarily in the United States, and returned to Europe as a trend product. The plant itself remained unchanged. Federkohl tolerates frost and is traditionally harvested only after the first cold nights, because that mellows its flavour. Its season falls in autumn and winter – precisely when the local range of vegetables otherwise thins out.

One of Europe's oldest forms of cabbage

Kale is not a new discovery; it is one of the oldest cultivated forms of cabbage of all. The non-heading leafy cabbages were already grown around the Mediterranean and in Europe in antiquity and are considerably older than the head cabbage bred later. Over the centuries, numerous regional variants emerged – from curly kale to the dark palm kale (known in Italy as cavolo nero) to hardy local varieties that survive harsh winters. In Switzerland and across much of Central Europe it was, for generations, a reliable winter vegetable that still stood in the field when little else grew. That, of all things, this down-to-earth vegetable was rediscovered as a global trend product says more about marketing than about nutritional value – which was there the whole time.

What "superfood" actually means – and what it does not

"Superfood" sounds like a distinction, but it is not a legally defined or protected term. In the European Union, the word may only be used on foods since 2007 if it is accompanied by an authorised nutrition or health claim – as set out in Regulation (EC) No 1924/2006 on nutrition and health claims. The background: without such rules, almost any food could be advertised as "super". In practice this means that whether a vegetable is nutrient-rich is decided not by the label but by its actual composition. And with kale, that can be read soberly in figures – entirely without an advertising word.

What is in 100 grams of kale – and how it compares

Kale is among the most nutrient-dense vegetables in our latitudes. The values below refer to raw kale per 100 grams; they vary by cultivar, soil, season and database.

Nutrient (per 100 g, raw)	Kale	For comparison
Vitamin C	about 90–120 mg	orange: about 53 mg
Vitamin K	about 250–390 µg	several times the reference value
Calcium	about 150 mg	one of the calcium-richest cultivated vegetables
Beta-carotene (provitamin A)	plentiful	as in carrots
Lutein and zeaxanthin	plentiful	among the leading leafy-green sources
Iron	about 1.5 mg	notable for a leafy vegetable
Protein	about 3–4 g	high for a vegetable

The body uses vitamin C among other things for collagen formation; vitamin K is involved in blood clotting; the body converts beta-carotene into vitamin A as needed. Lutein and zeaxanthin accumulate in the macula of the retina – research is examining their role in the eye. These are general physiological functions of these substances, not a promise of what eating kale does in an individual case.

Why preparation decides how much actually reaches you

The frequently cited vitamin C comparison applies to raw kale. Vitamin C and folate are sensitive to heat, light and oxygen. Traditionally, kale is cooked for a long time, sometimes over an hour – which markedly reduces part of these heat-labile vitamins. Anyone wanting to retain as much as possible cooks briefly and gently, or uses frozen kale, which is flash-frozen right after harvest and thereby keeps much of its vitamin content.

Raw, kale can be prepared as a salad; the firm leaves become more tender if you "massage" them with a little oil. A little fat in the dish makes sense anyway, because the body absorbs the fat-soluble carotenoids such as beta-carotene and lutein more readily with some oil.

Practical notes for buying and cooking: fresh kale keeps for a few days wrapped in a damp cloth in the vegetable drawer. Before preparation, cut the curly leaves from the firm central stem, which stays tough. Besides salad, brief steaming and the classic side dish, the leaves also work in soups and stews or – baked crisp in the oven – as chips. Frozen kale can be used directly.

With calcium, it is not just the amount that counts, but the uptake

A high nutrient content says nothing yet about how much of it the body can actually use. With calcium, kale has an advantage here: it is calcium-rich and at the same time low in oxalic acid (under 10 mg per 100 g). Oxalic acid binds calcium and hinders its uptake – which is why the abundant calcium in spinach is poorly available.

Small human studies using isotope-labelled calcium have examined this: in a controlled study of eleven women, calcium from kale was well absorbed – comparably well to calcium from milk (Heaney & Weaver, 1990). A follow-up study of fifteen women confirmed an absorption rate of roughly half the calcium present in kale (Heaney et al., 1993). Both are small but methodologically sound human studies; the finding is directionally reliable, even though individual values vary from person to person.

Local instead of flown-in trend greens

The practical advantage of kale lies in its origin: as a local winter vegetable it grows in Switzerland and Europe rather than travelling long distances. In the cold season it is available fresh; outside its season, frozen kale – flash-frozen right after harvest – retains much of its nutrient content, unlike many imported "superfood" leafy greens and powders with long transport routes. A similar nutrient density does not require an exotic trend product.

Safety and use

As a food, kale is harmless for most people. One point nonetheless deserves attention: the very high vitamin K content is relevant for people taking blood-thinning medication of the vitamin K antagonist type. What matters then is less avoidance than a consistent intake; the dosage is set medically to the usual diet. Anyone taking such medication should discuss larger changes in quantity with their doctor.

Like all brassicas, kale contains glucosinolates. In very large amounts and eaten raw, these can affect the thyroid in sensitive individuals; in usual portions this is not an issue. Wash thoroughly before preparation. As a normal part of a varied diet, kale is usually unproblematic during pregnancy and breastfeeding and for children.

Conclusion: a down-to-earth vegetable with real inner values

The "superfood" label is marketing – the nutrient density of kale is not. It provides plenty of vitamin C, an exceptional amount of vitamin K, well-available calcium and a range of secondary plant compounds, and it does so as a local winter vegetable with short transport routes. Preparation is decisive: the gentler it is, the more of the heat-sensitive vitamins is retained. What is well documented is the nutrient density and the availability of the calcium; much of what advertising broadly attributes to exotic trend products remains open. A nutrient-rich plate in winter does not require an import.

This article is for general information and does not replace medical or nutritional advice. If you have existing health conditions or take medication – particularly blood-thinning agents – seek professional advice before making major dietary changes.