Ask Eirik: How Many Bacteria Are There in Sauerkraut?

homemade-sauerkrautA few months back, I was contacted by a British TV production company called Ricochet. They were in the process of planning the third season of a show called Superfoods: The Real Story and were looking for a scientific project about sauerkraut – one of the foods they focus on in season 3 – that they could feature on the programme. They had come across the protocol for the clinical trial I’m conducting on sauerkraut and irritable bowel syndrome and wanted to know whether I would be willing to appear on camera and discuss our project. I was happy for the opportunity to talk about my work/research on camera and said I would gladly appear on the show.

Yesterday, we shot the segment on sauerkraut at a medical facility in my hometown. It was a lot of fun. The presenter on the show, Kate, asked me a lot of questions about fermented vegetables, the human microbiome, nutrition, and so forth. Many of the questions she asked me revolve around topics that I think a lot of people – in particular the type of people that follow blogs such as this one – are interested in.

Unfortunately, most of my answers are probably going to be lost in the editing process; hence, they will never make it to the screen. For that reason, I thought I’d answer some of the questions here on the blog, so that you – the readers of – get to hear my thoughts on the things we talked about. I thought I’d focus on the microbes that are present in sauerkraut, as I think it’s an interesting theme.

The following questions form the basis of today’s edition of Ask Eirik:

How many bacteria are there in sauerkraut?

Sub-questions: What types of bacteria are there? Do all of these organisms survive past the stomach acid, and do they all colonize the gut?

My answers

– Question 1: How many bacteria are there in sauerkraut?

Fermented foods are packed with bacteria! A recent review paper entitled Health benefits of fermented foods: microbiota and beyond had the following to say about the concentrations of microorganisms in fermented foods such as kimchi and sauerkraut:

 … some of the most familiar fermented foods, including sauerkraut, kimchi, kefir, dry fermented sausage, yogurt, cheese, kombucha, and miso ordinarily contain viable cells in notable quantities ranging between 106 and 109 cells/g or cells/ml. A relatively large fraction of those microbes survives passage through the human digestive tract. The ingestion of fermented foods potentially increases the numbers of microbes in the diet by up to 10 000-fold … (1)

Read the last sentence on more time and then take a second to let what it says sink in… As you can see, the consumption of fermented foods can dramatically increase the number of bacteria you get through your diet. As I’ll get to later, this can be both a good and a bad thing.

But what about sauerkraut specifically? Do we know how many bacteria that are present in a jar of sauerkraut? Some time ago, the famous health guru Dr. Mercola sent his sauerkraut off to a lab for analysis. Here’s what that the site had to say about the results of that analysis:

Dr. Mercola sent his sauerkraut off to a lab and reported the findings of probiotics saying, “We had it analyzed. We found in a 4-6 ounce serving of the fermented vegetables there were literally ten trillion bacteria.” That means 2 ounces of home fermented sauerkraut had more probiotics than a bottle of 100 count probiotic capsules. Translated this means one 16 ounce of sauerkraut is equal to 8 bottles of probiotics. (2)

That’s pretty crazy to think about… According to this test, just 2 ounces (about 60 grams) of sauerkraut contain more bacteria than a jar of probiotic capsules!

Perhaps needless to say, the amounts of bacteria that are present in sauerkraut will depend on a range of factors, including fermentation method (the sauerkraut Dr. Mercola tested was produced with the use of a probiotic starter culture), fermentation time, the amount of salt used, and fermentation temperature. Also, it’s important to point out that this test, initiated by Dr. Mercola, isn’t necessarily 100% valid. It may be that some of the measurements are slightly off or that some things got lost in translations. That said, I think it’s safe to say that sauerkraut is filled with bugs!

– Question 2: What types of bacteria are present in sauerkraut?

It’s not just the quantity of bacteria that’s important, but also the diversity… This leads us over to the first sub-question posed earlier, which was: What types of bacteria are present in sauerkraut?

A 2007 study answers exactly that question. It examined the microbiota of commercial sauerkraut fermentations and found the following:

Previous studies using traditional biochemical identification methods to study the ecology of commercial sauerkraut fermentations revealed that four species of lactic acid bacteria, Leuconostoc mesenteroides, Lactobacillus plantarum, Pediococcus pentosaceus, and Lactobacillus brevis, were the primary microorganisms in these fermentations. In this study, 686 isolates were collected from four commercial fermentations and analyzed by DNA fingerprinting. The results indicate that the species of lactic acid bacteria present in sauerkraut fermentations are more diverse than previously reported and include Leuconostoc citreum, Leuconostoc argentinum, Lactobacillus paraplantarum, Lactobacillus coryniformis, and Weissella sp. The newly identified species Leuconostoc fallax was also found. (3)

Below is a figure showing the major types of bacteria that are present in commercial sauerkraut fermentations.

As you can see, the microbiota changes during the fermentation process. Different types of microbes dominate at different stages, which is to be expected, as the oxygen levels and pH of the ferment change during the fermentation process. Different microbes are adapted to different conditions and their reproductive fitness will therefore depend on the conditions of the space they find themselves in.

Keep in mind: the bacteria shown in the figure above are not the only types of bacteria that are present in sauerkraut. Other microbes are present as well, albeit in lower concentrations. Also, it should be noted that the microbiota of homemade sauerkraut differs somewhat from that of mass-produced sauerkraut. Many of the same types of bacteria dominate in homemade ferments, but the structure and diversity of the microbial ecosystem differ somewhat.

– Question 3: Do all of the bacteria that are present in sauerkraut survive past the stomach acid, and do they all colonize the gut?

The bacteria that are present in sauerkraut and other fermented foods are adapted to live in low pH conditions, and many (probably most) of them survive past the stomach acid (1). As for the second question, the short answer is no! Most of the microbes that are found in fermented foods tend to be transient; that is, they only pass through the digestive system, they don’t colonize it. That said, some of the bacteria found in sauekraut and other fermented vegetables are probably able to set up shop in the lower gut. Not all, but some!

This is the main reason why I recommend to eat a wide diversity of homemade, fermented vegetables. Each batch of fermented vegetables has a unique microbiota composition. By eating several different types, you increase the likelihood that you’re ingesting microbes that are able to colonize your gut.

Last words

Before we wrap up, I want to loop back to the thing I mentioned earlier about the pros and cons of the high concentrations of bacteria that are present in sauerkraut. The fact that fermented vegetables are packed with bacteria can be both a good and a bad thing. The good thing is that the consumption of fermented vegetables can bring a lot of potentially beneficial microbes into the lower gut. The bad thing is that (excessive) consumption of fermented vegetables may destabilize the gut microbiota, hindering the development of a stable, resilient ecosystem.

This is one of the reasons why my general recommendation is to occasionally eat small quantities of a diversity of fermented vegetables. More isn’t necessarily better. I don’t think it’s a good idea to eat large quantities on a daily basis. That said, there’s a lot of inter-individual variability with regards to how much fermented vegetables that can be consumed without ill-effects. Some people have a higher tolerance than others. The health status and microbiota composition of the individual have to be taken into account when an appropriate intake level is to be determined.

Picture: Creative commons picture by Greg Willis. Some rights reserved.


  1. Yes it makes really sense, I think it depends on several factors, included our immune system.
    How we were born, how we trained it in our childhood, genetic and epigenetic factors that may contribute in a different way in the delicate host-microbiota interaction and feedback.
    I read the latest article about the Inuit microbiota, much less diverse than Hadza.
    I expected such result since the higher the latitude, the smaller is biodiversity.
    I’ve been wondering if European descendants and nordic people have in someway adapted to harbor a “less rich” and surely different microbiota than african tribes.
    Maybe we had some selective pressures that drove genetic/epigentic changes toward a different microbiotic/metabolome profile.
    Who knows?

  2. I have called 2 reputable sauerkraut companies In Oregon and Washington regarding the total number of bacteria per bottle. Both companies ferment for roughly 6 weeks, which is longer than most companies. The total per 16 oz for each company was between 2-5 billion organisms per jar. Quite a bit less than the mercola number. He might have been looking at cells, rather than living organisms.

    • Hi Scott,

      I’m not sure exactly what kind of tests Dr. Mercola did. As I point out in the article, I don’t have 100% confidence in his analysis. I put more faith in the numbers put forth in the first review paper I bring up in the article.

      That said, there is no doubt that sauerkraut is packed with bacteria, and is a lot more potent than the average probiotic supplement.

      The numbers you refer to can’t be correct. 2-5 billion CFU is less than what you find in just one capsule of a low-potency probiotic supplement. Either the companies you’ve been talking to are just throwing out some random numbers, or you must have misunderstood them.

      Thanks for your comment.

      • It is correct and it states in on the outside of the bottle for both companies. Look at the label for Oregon Brineworks. It says it contains “billions of bacteria in every jar.” I called them to clarify exactly how much and they said roughly 4 billion. I had the same conversation with another company and they had the same result. Take a look at the link below

        • Okay.

          Thanks for clarifying. The relatively low number of CFUs in their products may partly be explained by the very long fermentation time.

          I think the key takeaway here is that the concentrations of bacteria in sauerkraut vary greatly (as I point out in the article), depending on fermentation method, the amount of salt used, fermentation time, and more.

          This article gives an overview of the microbial counts in commercial sauerkraut fermentations: (Scroll down to the results of the microbiological analysis)

  3. Interesting article. Thanks, Eirik.

  4. Troy Teegerstrom says:

    I guess you can count me as one of the silent majority who read your stuff and really enjoy it!!! keep up the good work!!!

    • Hi Troy,

      I’m glad you stepped out of the shadows. Feel free to put up more comments if there’s ever anything about my articles you find unclear or want to comment on.

  5. Koreans eat Kimchi daily, often with multiple meals, and it seems to be okay for them. I wouldn’t think Sauerkraut daily (with dinner?) would be bad.

  6. Wow! Increasing the amount of microbes in the gut by ten thousand fold is something that I think every person would benefit from. I need to definitely invest in eating more fermented food, I do not eat it enough. I think even going as far as to attempting to make it at home would be beneficial. Thank you for this extremely informative and science-based article on the study you did on bacteria. Really great in helping me understand the nitty gritty when it comes to gut bacteria.


  1. […] with respect to their environmental preferences. Some bacteria, such as Lactobacillus plantarum, the dominant type of bacteria in fermented foods such as sauerkraut, thrive under very acidic conditions, whereas others are incapable of surviving in low pH […]

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