Sauerkraut

Sauerkraut is one of the oldest and simplest foods people have ever made: shredded cabbage, a little salt, and time. Left in its own brine, the cabbage slowly sours as friendly bacteria turn its natural sugars into tangy lactic acid. The result keeps for months without refrigeration, tastes bright and crunchy, and carries a genuinely interesting nutritional story — enough vitamin C to have helped keep sailors alive on long voyages, fiber that feeds your gut, and, in the raw unpasteurized version, a dose of living cultures. This page explains what sauerkraut is, how the fermentation actually works, what it does and does not deliver nutritionally, the delightful history of scurvy and Captain Cook, what the research says about probiotics and digestion, and the honest caveats — especially its high salt content and the fact that most canned sauerkraut has no live cultures left at all. We will keep the evidence in perspective: sauerkraut is a nourishing, inexpensive food, not a medicine.

Table of Contents

  1. What Sauerkraut Is and How Lacto-Fermentation Works
  2. Nutritional Profile
  3. Nutrients the Fermentation Creates: K2, C, and B Vitamins
  4. The Scurvy Story: Captain Cook and Vitamin C at Sea
  5. Probiotics and Gut Health
  6. Immune and Digestive Research
  7. Biogenic Amines and Histamine: A Caveat
  8. Raw vs. Pasteurized: The Most Important Buying Tip
  9. Sodium: Who Should Go Easy
  10. How to Choose, Make, and Store Sauerkraut
  11. Research Papers
  12. Connections
  13. Featured Videos

What Sauerkraut Is and How Lacto-Fermentation Works

Sauerkraut — German for "sour cabbage" — is finely shredded green cabbage that has been preserved by lacto-fermentation. There is no vinegar involved in traditional sauerkraut. The sourness comes entirely from acid that bacteria make on the spot. The recipe is almost comically simple: cabbage and salt, packed tightly so the cabbage sits under its own liquid, away from air.

Here is what actually happens. When you massage salt into shredded cabbage — usually about 2 percent of the cabbage's weight, roughly one tablespoon of salt per pound and a half — the salt draws water out of the leaves by osmosis. Within a few hours the cabbage is sitting in a puddle of salty brine. That brine does two crucial jobs. It holds back the spoilage bacteria and molds that would rot the vegetable, and it creates a low-oxygen, salt-tolerant environment that a specific family of microbes loves.

Those microbes are lactic acid bacteria (LAB), and they are already living on the cabbage leaves when you buy it — you do not add a starter culture. The fermentation runs in a natural relay. Early on, a species called Leuconostoc mesenteroides takes the lead, producing carbon dioxide (the reason a fresh crock bubbles) and beginning to sour the brine. As acidity climbs and oxygen disappears, more acid-tolerant species in the Lactobacillus family — especially Lactiplantibacillus plantarum — take over and drive the pH down to around 3.4 to 3.6. At that point the cabbage is thoroughly sour, hostile to almost anything that could spoil it, and shelf-stable.

The transformation takes anywhere from a few days to several weeks depending on temperature: warmer means faster and softer, cooler means slower and crunchier with more complex flavor. The whole thing works only because the cabbage stays submerged. Exposed to air, kraut grows surface yeast and mold; kept under the brine, it is one of the safest and most forgiving ferments a beginner can make.

Nutritional Profile

Sauerkraut is a genuinely low-calorie, nutrient-dense food. A one-cup serving (about 140 grams, drained) has only around 25 to 30 calories and essentially no fat, yet it delivers meaningful fiber, vitamin C, vitamin K, and a range of minerals. Because it starts as cabbage — a cruciferous vegetable — it also carries the plant compounds that make that family interesting, including glucosinolate breakdown products.

Roughly, a one-cup serving of sauerkraut provides:

The one figure you should keep front of mind is sodium. Sauerkraut is a salt-cured food, so a single cup can carry anywhere from roughly 900 to 1,500 milligrams of sodium — a large slice of the day's recommended limit. That is not a reason to avoid it, but it is the reason sauerkraut is a condiment-sized food for most people rather than a bowlful, and a food some people need to watch closely. We return to sodium in its own section.

Nutrients the Fermentation Creates: K2, C, and B Vitamins

One of the quietly remarkable things about sauerkraut is that fermentation does not just preserve the cabbage's nutrients — in some cases it adds to them. The bacteria are living organisms with their own metabolism, and as they work they synthesize compounds the raw vegetable never had.

The most talked-about example is vitamin K2 (menaquinones). Cabbage naturally contains vitamin K1, the plant form. Certain lactic acid bacteria convert some of that into vitamin K2, a form the body uses to help direct calcium into bones and away from arteries. Be honest about scale, though: sauerkraut supplies only a modest, variable amount of K2 — nothing like the powerhouse levels found in the Japanese fermented soybean natto. Sauerkraut is a nice contributor to K2 intake, not a megadose.

Fermentation also tends to preserve and sometimes increase certain B vitamins, including folate and B12-related activity produced by some bacterial strains, and it can make minerals more available by breaking down anti-nutrients such as phytates that otherwise bind them. And crucially, the acidic, oxygen-free brine protects vitamin C. Vitamin C is fragile — heat and air destroy it — but in a sealed crock of sour brine it survives remarkably well, which is exactly why sauerkraut could be stored for months and still fight scurvy.

The Scurvy Story: Captain Cook and Vitamin C at Sea

For centuries, long sea voyages were haunted by scurvy, the disease of vitamin C deficiency. Sailors' gums would swell and bleed, old wounds would reopen, teeth would loosen, and men would waste away and die — sometimes half a crew on a single voyage. No one understood the cause; fresh food simply ran out weeks from land, and with it the vitamin C the body cannot make or store for long.

Enter sauerkraut. Because its vitamin C survived months in the barrel, salted cabbage became one of the practical answers to a deadly problem. The most famous chapter belongs to the British explorer Captain James Cook. On his great Pacific voyages beginning in 1768, Cook carried large quantities of sauerkraut and insisted his crews eat it. Over years at sea, he lost astonishingly few men to scurvy — a feat so notable that the Royal Society awarded him its Copley Medal in 1776 in part for showing how to keep a ship's crew healthy.

It is a wonderful story, and it is worth telling accurately. Cook did not rely on sauerkraut alone: he also took on fresh greens and other foods at every port, brewed "wort" from malt, and ran an unusually clean, disciplined ship. Historians who have re-examined the record, such as Baron in a 2009 reassessment, point out that the conquest of scurvy was messier and more gradual than the tidy legend suggests — James Lind's famous 1747 citrus trial, the later Royal Navy adoption of lemon and lime juice, and shipboard sauerkraut were overlapping pieces of a long puzzle. Sauerkraut's vitamin C content is real but modest, so its success at sea came from consistency and quantity as much as potency. Still, the core of the tale holds up: a barrel of sour cabbage genuinely helped carry sailors safely across the world's oceans, and that is a rare case of a humble fermented food changing history.

Probiotics and Gut Health

Raw, unpasteurized sauerkraut is a living food. Each spoonful of a well-made batch can contain large numbers of lactic acid bacteria — the same kinds of microbes studied as probiotics. This is the source of sauerkraut's reputation as a gut-health food, and there is a real basis for it: eating live microbes and the fibers and metabolites that come with them is one plausible way to nourish the community of bacteria in your own intestines.

But it pays to be precise about what sauerkraut is and is not. It is a source of live microbes; it is not a standardized probiotic supplement. The specific strains, their numbers, and how many survive the acid of your stomach to reach the colon all vary batch to batch and are not measured or guaranteed the way they are for a labeled probiotic capsule. The bacteria in sauerkraut are not proven to permanently colonize the gut — like most food-borne microbes, they are largely visitors passing through. What they may do while passing through — producing beneficial acids, nudging the resident community, interacting with the immune tissue that lines the gut — is an active and promising area of study rather than settled fact.

There is one more honest wrinkle, and it matters enough to have its own section below: only raw, unpasteurized sauerkraut carries live cultures. The canned and jarred "shelf-stable" sauerkraut that fills most grocery shelves has been heated to make it last, and heat kills the bacteria. That kraut is still a fine, fibrous, vitamin-C-bearing vegetable — but as a probiotic it is inert.

Immune and Digestive Research

What does the science actually show? The strongest evidence is for fermented foods as a broad category rather than for sauerkraut specifically. In a widely cited 2021 Stanford study published in Cell, Wastyk and colleagues put healthy adults on a diet high in fermented foods — yogurt, kefir, kimchi, vegetable brine ferments like sauerkraut, and others — for ten weeks. The fermented-food group showed greater gut microbial diversity and lower levels of several inflammatory markers, an encouraging signal that regularly eating these foods can shift the body in a favorable direction. Sauerkraut belongs squarely in that food family.

Sauerkraut has also been looked at on its own, though usually in small studies. A 2018 pilot trial by Nielsen and colleagues in Food & Function gave people with irritable bowel syndrome (IBS) sauerkraut for six weeks and found improvement in symptoms — interestingly, whether the sauerkraut was raw or pasteurized. That result is a useful reminder that some of sauerkraut's benefit may come from its fiber and the compounds fermentation leaves behind, not from live bacteria alone. It was a small pilot without a no-sauerkraut comparison group, so it points a direction rather than proving a treatment. More recent work, such as a 2025 crossover trial by Schropp and colleagues in Microbiome, has begun tracking in detail how several weeks of daily sauerkraut shifts the gut community in healthy people, adding needed rigor to a field that has leaned heavily on lab studies and small pilots.

The reasonable takeaway: eating fermented vegetables like sauerkraut as part of a varied, fiber-rich diet is associated with a healthier gut environment and lower inflammation, the evidence is growing and genuinely promising, and it is not yet strong enough to promise that sauerkraut treats any specific disease. Enjoy it as good food that plausibly supports your gut, and keep expectations grounded.

Biogenic Amines and Histamine: A Caveat for Sensitive People

Fermentation has a small downside worth knowing about. As bacteria break down proteins in the cabbage, they produce compounds called biogenic amines — most notably histamine, along with tyramine, putrescine, and others. In most people these amounts are harmless and quickly cleared. But a minority of people have histamine intolerance: they produce too little of the enzyme (diamine oxidase) that breaks histamine down, so histamine-rich foods can trigger headaches, flushing, a runny nose, hives, or digestive upset.

Aged and fermented foods — sauerkraut very much included — are among the higher-histamine foods, as reviewed by Comas-Basté and colleagues in 2020. The longer a kraut ferments and ages, the more biogenic amines it tends to accumulate. People who react to histamine, and people taking MAO-inhibitor medications (which block the breakdown of tyramine and can cause dangerous blood-pressure spikes), should be cautious with sauerkraut and other fermented foods. For everyone else, this is not a concern — just a reason to notice how your own body responds. If sauerkraut reliably gives you a headache or flush, histamine is a likely culprit and moderation or fresher, shorter-fermented kraut may help.

Raw vs. Pasteurized: The Most Important Buying Tip

If you remember one practical thing from this page, make it this: raw and pasteurized sauerkraut are nutritionally different products, and the label rarely makes it obvious.

The rows of cans and jars sitting unrefrigerated in the middle of the store are pasteurized — heated during processing so they keep at room temperature. That heat destroys the live cultures. You still get the fiber, the vitamin C (somewhat reduced by heat), the tang, and the minerals, so it is a perfectly good vegetable. But it is not a probiotic food, and no amount of "traditionally fermented" wording on the front changes that once it has been cooked in the can.

The raw, live-culture sauerkraut is almost always in the refrigerated section, in a jar or pouch. Look for the words raw, unpasteurized, live cultures, or naturally fermented, and make sure the ingredient list is short — essentially cabbage and salt. Two warnings on the label are especially telling:

Note that not every refrigerated kraut is raw — some brands pasteurize and then refrigerate for texture or shelf life — so the wording on the label is what settles it. When you want the gut-microbe benefit, buy refrigerated, raw, unpasteurized, cabbage-and-salt sauerkraut, and add it to meals uncooked. Heating raw kraut in a hot pan kills the same cultures you paid extra for; stir it in at the end or serve it cold alongside.

Sodium: Who Should Go Easy

Salt is not an optional garnish in sauerkraut — it is what makes the fermentation safe by holding back spoilage organisms while the good bacteria get established. That means sauerkraut is inherently a high-sodium food, and there is no live-culture kraut that is also low in salt. A single cup can supply a large share of the day's recommended sodium ceiling.

For a healthy person eating sauerkraut in condiment-sized amounts — a few forkfuls alongside a meal — this is a non-issue. But some people should be deliberate about it:

A few practical moves reduce the load without ruining the food: eat modest portions, drain (and if needed briefly rinse) the kraut to wash off surface brine, and balance a salty forkful of sauerkraut with an otherwise low-salt meal built around fresh vegetables and unprocessed foods. Rinsing does cost you some of the surface bacteria and vitamin C, so it is a trade-off — a reasonable one if sodium is a real medical concern for you.

How to Choose, Make, and Store Sauerkraut

Choosing. As covered above, for living cultures buy refrigerated, raw, unpasteurized sauerkraut with a two-ingredient label of cabbage and salt and no vinegar. For a simple side vegetable where cultures do not matter, the canned or jarred pasteurized kraut is inexpensive and fine.

Making your own. Homemade sauerkraut is one of the safest ferments for a beginner, and it costs almost nothing. The basic method:

  1. Shred a head of cabbage finely and weigh it.
  2. Add 2 percent of that weight in salt (about 1 tablespoon of salt per 1.5 to 2 pounds of cabbage). Use plain salt without added iodine or anti-caking agents if you can.
  3. Massage and squeeze the salted cabbage for several minutes until it releases enough liquid to pool.
  4. Pack it tightly into a clean jar or crock so the cabbage is fully submerged under its own brine — a weight or a folded cabbage leaf on top helps keep it down and away from air.
  5. Cover loosely (so fermentation gas can escape) and leave it at cool room temperature. Taste after a few days; it is usually ready somewhere between one and four weeks, depending on temperature and how sour you like it.
  6. When it tastes right, seal it and move it to the refrigerator.

A little foamy activity and a sour smell are normal and good. Discard a batch only if you see fuzzy colored mold, or if it smells genuinely rotten or putrid rather than pleasantly sour — a white film of harmless surface yeast (kahm yeast) can simply be skimmed off.

Storing. Kept cold and submerged in its brine, raw sauerkraut lasts for many months in the refrigerator, slowly growing more sour over time. Always use a clean utensil, and push the cabbage back under the brine after serving. Pasteurized canned kraut keeps for a long time unopened on the shelf and, once opened, for a couple of weeks in the fridge. Freezing is possible but softens the texture and, for raw kraut, harms the live cultures — so refrigeration is the better home for a good jar of sauerkraut.

Research Papers

  1. Wastyk HC, Fragiadakis GK, Perelman D, et al. Gut-microbiota-targeted diets modulate human immune status. Cell. 2021;184(16):4137-4153.e14. doi:10.1016/j.cell.2021.06.019 — a 10-week diet high in fermented foods raised gut microbial diversity and lowered inflammatory markers in healthy adults.
  2. Schropp N, Bauer A, Stanislas V, et al. The impact of regular sauerkraut consumption on the human gut microbiota: a crossover intervention trial. Microbiome. 2025;13(1). doi:10.1186/s40168-024-02016-3 — a controlled crossover trial tracking how several weeks of daily sauerkraut shift the gut community in healthy people.
  3. Marco ML, Sanders ME, Gänzle M, et al. The International Scientific Association for Probiotics and Prebiotics (ISAPP) consensus statement on fermented foods. Nature Reviews Gastroenterology & Hepatology. 2021;18(3):196-208. doi:10.1038/s41575-020-00390-5 — the expert consensus defining fermented foods and reviewing the state of the health evidence.
  4. Marco ML, Heeney D, Binda S, et al. Health benefits of fermented foods: microbiota and beyond. Current Opinion in Biotechnology. 2017;44:94-102. doi:10.1016/j.copbio.2016.11.010 — reviews the mechanisms by which fermented foods may act on health, live microbes and metabolites alike.
  5. Dimidi E, Cox SR, Rossi M, Whelan K. Fermented foods: definitions and characteristics, impact on the gut microbiota and effects on gastrointestinal health and disease. Nutrients. 2019;11(8):1806. doi:10.3390/nu11081806 — a clear review of what fermented foods are and their gastrointestinal effects.
  6. Nielsen ES, Garnås E, Jensen KJ, et al. Lacto-fermented sauerkraut improves symptoms in IBS patients independent of product pasteurisation — a pilot study. Food & Function. 2018;9(10):5323-5335. doi:10.1039/c8fo00968f — a small pilot in which both raw and pasteurized sauerkraut improved IBS symptoms over six weeks.
  7. Zabat MA, Sano WH, Wurster JI, Cabral DJ, Belenky P. Microbial community analysis of sauerkraut fermentation reveals a stable and rapidly established community. Foods. 2018;7(5):77. doi:10.3390/foods7050077 — documents the lactic-acid-bacteria succession that drives a sauerkraut ferment.
  8. Touret T, Oliveira M, Semedo-Lemsaddek T. Putative probiotic lactic acid bacteria isolated from sauerkraut fermentations. PLOS ONE. 2018;13(9):e0203501. doi:10.1371/journal.pone.0203501 — characterizes sauerkraut bacteria as candidate probiotics.
  9. Raak C, Ostermann T, Boehm K, Molsberger F. Regular consumption of sauerkraut and its effect on human health: a bibliometric analysis. Global Advances in Health and Medicine. 2014;3(6):12-18. doi:10.7453/gahmj.2014.038 — surveys the published research on sauerkraut and health outcomes.
  10. Rezac S, Kok CR, Heermann M, Hutkins R. Fermented foods as a dietary source of live organisms. Frontiers in Microbiology. 2018;9:1785. doi:10.3389/fmicb.2018.01785 — explains why only unpasteurized ferments deliver live microbes, and how processing changes that.
  11. Comas-Basté O, Sánchez-Pérez S, Veciana-Nogués MT, Latorre-Moratalla M, Vidal-Carou MC. Histamine intolerance: the current state of the art. Biomolecules. 2020;10(8):1181. doi:10.3390/biom10081181 — reviews histamine intolerance and the high-histamine fermented and aged foods, sauerkraut among them.
  12. Baron JH. Sailors' scurvy before and after James Lind — a reassessment. Nutrition Reviews. 2009;67(6):315-332. doi:10.1111/j.1753-4887.2009.00205.x — a careful history of scurvy and its remedies, giving context to the Cook-and-sauerkraut legend.

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Connections

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