Kohlrabi

Kohlrabi is a pale-green (sometimes purple) vegetable that looks a little like a small alien spaceship — a round, swollen bulb sitting above the soil with leafy stems sprouting from its sides. Despite the odd shape, it is simply a member of the cabbage family, and its name says so plainly: kohlrabi comes from the German words for "cabbage" (Kohl) and "turnip" (Rabi), giving the common English nickname "cabbage-turnip." It is not actually a root, though. The part you eat is a thickened stem that swells above the ground, and it tastes mild, crisp, and faintly sweet — most people say it is like the tender heart of a broccoli stem crossed with a very gentle cabbage. Both the bulb and the leaves are edible, raw or cooked. This page explains what kohlrabi is, what nutrition it delivers (it is genuinely rich in vitamin C and a good source of fiber), what the science on cruciferous vegetables and their sulfur compounds does and does not show, and the practical side: how to pick a tender one, peel it, and cook it. As always, the tone here is honest — kohlrabi is a nourishing, low-calorie vegetable, not a cure for anything.

Table of Contents

  1. What Kohlrabi Is
  2. Nutritional Profile
  3. Vitamin C and Fiber Benefits
  4. Glucosinolates and Isothiocyanates
  5. Gut Health and Digestion
  6. Blood Sugar, Weight, and Low Calorie Density
  7. How to Select, Prepare, and Cook
  8. How to Store Kohlrabi
  9. Safety and Who Should Be Cautious
  10. Research Papers
  11. Connections
  12. Featured Videos

What Kohlrabi Is

Kohlrabi is a cruciferous vegetable — a cultivated form of Brassica oleracea, the same remarkable species that, through centuries of selective breeding, also gave us cabbage, broccoli, cauliflower, kale, Brussels sprouts, and collard greens. Each of those familiar vegetables is the same wild plant coaxed to overdevelop a different part: cabbage is a swollen leaf bud, broccoli and cauliflower are flower heads, kale is the leaves, and kohlrabi is the stem. Specifically, the plant channels its growth into a short section of stem just above the ground, which balloons into the round, crisp bulb we harvest. Because it is a stem rather than a root, kohlrabi sits on top of the soil, not buried in it — a useful detail that distinguishes it from true root vegetables like turnips or radishes despite the "cabbage-turnip" nickname.

Two things surprise people who try it for the first time. First, the flavor is gentle: raw kohlrabi is juicy and crunchy with a clean, mildly sweet, slightly peppery taste, closest to a broccoli stalk or a very mild cabbage, and without the bite of a radish. Second, the whole plant is usable. The bulb is peeled and eaten raw in slaws and salads or cooked in almost any way you would cook a turnip or a potato, and the leaves — which are essentially small, tender collard or kale greens — can be sautéed or added to soups rather than thrown away. Kohlrabi comes in two main colors, a pale green and a striking purple, but the purple skin is only skin-deep: peel either one and the flesh inside is the same creamy white.

Nutritional Profile

Kohlrabi's biggest nutritional selling point is that it delivers a lot of nutrition for very little energy. A one-cup serving of raw kohlrabi (about 135 grams) contains only around 36 calories, yet it supplies well over a day's worth of vitamin C along with a solid dose of fiber. Per 100 grams, raw kohlrabi runs roughly 27 calories, about 6 grams of carbohydrate, 3.6 grams of fiber, and close to 2 grams of protein, with almost no fat. The rest of the profile is a broad, useful spread rather than a single blockbuster nutrient. The figures below are approximate values for the raw, peeled bulb and will shift a little with variety, size, and cooking.

Vitamins that kohlrabi supplies in worthwhile amounts include:

On the mineral side, kohlrabi offers:

Beyond vitamins and minerals, kohlrabi provides a good amount of dietary fiber (mostly the kind that adds bulk and feeds gut bacteria) and, like every cabbage-family vegetable, a group of sulfur-containing plant compounds called glucosinolates. Those two features — the fiber and the glucosinolates — are what make kohlrabi more interesting than its modest calorie count suggests, and each gets its own section below.

Vitamin C and Fiber Benefits

The two nutrients kohlrabi delivers most generously are also two of the best-established in nutrition science, which is a nice change from vegetables whose reputations rest on shaky claims.

Vitamin C

Vitamin C (ascorbic acid) is an essential vitamin humans cannot make, so we must get it from food. It is a powerful water-soluble antioxidant, and it is required to build collagen, the structural protein that holds skin, blood vessels, gums, and connective tissue together — which is why severe, prolonged vitamin C deficiency causes scurvy. Vitamin C also supports several parts of the immune system and helps the body absorb iron from plant foods. Because a cup of kohlrabi can cover an adult's entire daily vitamin C need, it is a legitimately excellent everyday source, especially raw, since vitamin C is partly destroyed by heat and leaches into cooking water. The honest caveat is that vitamin C's benefits come from preventing deficiency and meeting daily needs; megadoses have not been shown to work miracles, and the body simply excretes what it cannot use.

Fiber

Dietary fiber is the other reliable win. Most people eat far less fiber than recommended, and kohlrabi's roughly 3.6 grams per 100 grams helps close that gap. Fiber adds bulk that keeps digestion moving, supports regularity, feeds beneficial gut bacteria, and contributes to fullness so you feel satisfied on fewer calories. Large reviews of dietary patterns consistently link higher fiber intake with lower risks of heart disease, type 2 diabetes, and other chronic conditions — not because any single food is magic, but because fiber-rich eating is a hallmark of a healthy overall diet. Kohlrabi is a pleasant, low-calorie way to add to your daily fiber total.

Glucosinolates and Isothiocyanates

Here is where kohlrabi shares in the most-studied — and most-hyped — chemistry of the cabbage family, so it is worth being careful and honest about what is actually known.

What these compounds are

Every cruciferous vegetable, kohlrabi included, stores sulfur-containing compounds called glucosinolates. On their own these are inert, but when you chop, grate, or chew the vegetable, you rupture its cells and release an enzyme (myrosinase) that converts the glucosinolates into biologically active molecules called isothiocyanates — the best-known of which, from broccoli, is sulforaphane. These isothiocyanates are what much of the laboratory interest in cruciferous vegetables is really about. In cell and animal studies they can switch on the body's own detoxification and antioxidant defense enzymes and influence how cells handle damage and inflammation, which is the mechanistic reason cabbage-family vegetables show up so often in cancer-prevention research.

What the evidence does and does not show

This is the part where honesty matters. Population studies — the kind that track what large groups of people eat — have often found that people who eat more cruciferous vegetables tend to have somewhat lower rates of certain cancers. That is a real and encouraging signal. But it is an association, not proof of cause: people who eat lots of cabbage and broccoli usually differ from those who don't in dozens of ways (more vegetables overall, less processed food, other healthy habits), and the epidemiological findings are mixed rather than uniform. Meanwhile, the dramatic effects of isothiocyanates seen in the lab typically use concentrations far higher than a serving of vegetables provides, and few results have been confirmed in rigorous human trials. It is also worth knowing that most kohlrabi-specific data comes from studying the cabbage family as a whole, not kohlrabi in particular, and that cooking method changes the chemistry — boiling can leach and deactivate a large share of these compounds, while light steaming or eating some raw preserves more of them. The fair takeaway: kohlrabi belongs to a vegetable family with genuinely interesting, partly-tested biology, and eating it regularly fits every credible healthy-diet pattern — but it should be enjoyed as good food, not taken as a preventive medicine.

Gut Health and Digestion

Kohlrabi is a friendly food for digestion, mainly thanks to its fiber. Fiber is the part of plant food that human enzymes cannot break down, so it travels through to the colon largely intact. There it does two jobs. The insoluble portion adds bulk and holds water, which keeps stool soft and moving and supports comfortable regularity. The fermentable portion becomes food for the trillions of beneficial bacteria that live in the gut; as those microbes ferment it, they produce short-chain fatty acids such as butyrate, which nourish the cells lining the colon and help maintain a healthy gut barrier. Feeding your gut microbes a steady supply of plant fiber from vegetables like kohlrabi is one of the simplest, most food-first ways to support a diverse, active microbiome — no supplement required.

The same fermentation that benefits your gut bacteria, however, also produces gas, which is why some people feel bloated after a large serving of cruciferous vegetables. For most people this is mild and simply a sign the fiber is doing its job; for a minority with sensitive digestion it can be genuinely uncomfortable, and that trade-off is covered in the safety section below.

Blood Sugar, Weight, and Low Calorie Density

Kohlrabi fits comfortably into eating patterns aimed at steady blood sugar and a healthy weight, for one straightforward reason: it has very low energy density. That means it delivers a satisfying volume of food — water, fiber, crunch — for very few calories. A whole cup is only around 36 calories, so you can eat a generous, filling portion without much caloric cost, which naturally supports appetite control and weight management as part of a balanced plate. Reviews of dietary fiber and body weight consistently associate higher intake of fiber-rich, low-calorie foods with easier weight regulation.

On blood sugar, kohlrabi's carbohydrate is modest and comes packaged with fiber, so it is digested and absorbed more gently than refined starches or sugars, causing a smaller, slower rise in blood glucose. This makes kohlrabi a smart vegetable choice for anyone watching their blood sugar. It is important, though, not to overstate the point: eating kohlrabi is not a treatment for diabetes. The reasonable, evidence-consistent message is that it is a low-calorie, fiber-containing, non-refined carbohydrate that belongs in a blood-sugar-friendly diet — within an overall pattern, not as a stand-alone fix.

How to Select, Prepare, and Cook

Kohlrabi is one of the easier vegetables to handle once you know two things: pick a small one, and peel it well.

Selecting

Preparing

The one non-negotiable step is peeling. Kohlrabi's outer skin is tough and fibrous — especially on larger bulbs it can have a woody layer just beneath the surface — so trim off the stems and root end, then peel generously with a sharp paring knife or sturdy peeler until you reach the crisp, pale flesh. Don't discard the leaves: wash them and treat them like any hardy green. Once peeled, the bulb can be sliced, cut into matchsticks, grated, or diced.

Cooking

Kohlrabi is versatile and forgiving:

How to Store Kohlrabi

Kohlrabi keeps well, which is part of its appeal:

Safety and Who Should Be Cautious

For the vast majority of people, kohlrabi is an exceptionally safe, wholesome vegetable that can be eaten freely, raw or cooked. A few honest, specific notes are worth knowing:

None of these caveats change the basic picture for most households: kohlrabi is a nutritious, gentle, versatile vegetable that most people can enjoy without a second thought.

Research Papers

  1. Higdon JV, Delage B, Williams DE, Dashwood RH. Cruciferous vegetables and human cancer risk: epidemiologic evidence and mechanistic basis. Pharmacol Res. 2007;55(3):224–236. doi:10.1016/j.phrs.2007.01.009 — the key review weighing the epidemiology and the glucosinolate biology behind interest in the whole cabbage family.
  2. Fahey JW, Zalcmann AT, Talalay P. The chemical diversity and distribution of glucosinolates and isothiocyanates among plants. Phytochemistry. 2001;56(1):5–51. doi:10.1016/S0031-9422(00)00316-2 — foundational catalog of the sulfur compounds that kohlrabi shares with all cruciferous vegetables.
  3. Zhang Y, Talalay P, Cho CG, Posner GH. A major inducer of anticarcinogenic protective enzymes from broccoli: isolation and elucidation of structure. Proc Natl Acad Sci U S A. 1992;89(6):2399–2403. doi:10.1073/pnas.89.6.2399 — the discovery of sulforaphane, the best-known cruciferous isothiocyanate.
  4. Traka M, Mithen R. Glucosinolates, isothiocyanates and human health. Phytochem Rev. 2008;8(1):269–282. doi:10.1007/s11101-008-9103-7 — reviews how glucosinolates convert to active isothiocyanates and what that may mean for health.
  5. Verkerk R, Schreiner M, Krumbein A, Ciska E, et al. Glucosinolates in Brassica vegetables: the influence of the food supply chain on intake, bioavailability and human health. Mol Nutr Food Res. 2009;53(S2):S219–S265. doi:10.1002/mnfr.200800065 — explains how growing, storage, and especially cooking change the glucosinolate content you actually eat.
  6. Vermeulen M, Klopping-Ketelaars IWAA, van den Berg R, Vaes WHJ. Bioavailability and kinetics of sulforaphane in humans after consumption of cooked versus raw broccoli. J Agric Food Chem. 2008;56(22):10505–10509. doi:10.1021/jf801989e — direct human evidence that boiling sharply lowers absorbed isothiocyanates versus eating cruciferous vegetables raw.
  7. Aune D, Giovannucci E, Boffetta P, et al. Fruit and vegetable intake and the risk of cardiovascular disease, total cancer and all-cause mortality: a systematic review and dose-response meta-analysis. Int J Epidemiol. 2017;46(3):1029–1056. doi:10.1093/ije/dyw319 — large pooled analysis placing cruciferous vegetables within the broader benefit of vegetable-rich eating.
  8. Carr AC, Maggini S. Vitamin C and immune function. Nutrients. 2017;9(11):1211. doi:10.3390/nu9111211 — reviews the roles of the vitamin C that kohlrabi supplies so generously.
  9. Padayatty SJ, Levine M. Vitamin C: the known and the unknown and Goldilocks. Oral Dis. 2016;22(6):463–493. doi:10.1111/odi.12446 — a balanced overview of what vitamin C does, and where its benefits are and are not established.
  10. Reynolds A, Mann J, Cummings J, et al. Carbohydrate quality and human health: a series of systematic reviews and meta-analyses. Lancet. 2019;393(10170):434–445. doi:10.1016/S0140-6736(18)31809-9 — strong evidence linking higher dietary fiber intake with lower chronic-disease risk.
  11. Slavin JL. Dietary fiber and body weight. Nutrition. 2005;21(3):411–418. doi:10.1016/j.nut.2004.08.018 — reviews how fiber-rich, low-calorie foods like kohlrabi support satiety and weight management.
  12. Felker P, Bunch R, Leung AM. Concentrations of thiocyanate and goitrin in human plasma, their precursor concentrations in brassica vegetables, and associated potential risk for hypothyroidism. Nutr Rev. 2016;74(4):248–258. doi:10.1093/nutrit/nuv110 — puts the cruciferous "goitrogen" concern in realistic, dose-and-iodine context.

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Connections

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