What is sauerkraut

Sauerkraut is one of the most common and oldest forms of preserving cabbage (Brassica oleracea convar capitata var sabauda L) or pointed cabbage (Brassica oleracea var capitata f alba) that can be traced back as a food source to the 4th century BC ¹. Sauerkraut is usually produced by spontaneous fermentation that relies on lactic acid bacteria naturally present in white cabbage ². White cabbage is one of the most important vegetables grown worldwide. Cabbage contains considerable amounts of bioactive compounds such as glucosinolates, vitamin C, carotenoids, and polyphenols ³.

Sauerkraut is made by a process of pickling called lactic acid fermentation that is analogous to how traditional (not heat-treated) pickled cucumbers and kimchi are made. The cabbage is finely shredded, layered with salt, and left to ferment. Fully cured sauerkraut keeps for several months in an airtight container stored at 15 °C (60 °F) or below. Neither refrigeration nor pasteurization is required, although these treatments prolong storage life.

Fermentation by lactobacilli is introduced naturally, as these air-borne bacteria culture on raw cabbage leaves where they grow. Yeasts also are present, and may yield soft sauerkraut of poor flavor when the fermentation temperature is too high. The fermentation process has three phases, collectively sometimes referred to as population dynamics. In the first phase, anaerobic bacteria such as Klebsiella and Enterobacter lead the fermentation, and begin producing an acidic environment that favors later bacteria. The second phase starts as the acid levels become too high for many bacteria, and Leuconostoc mesenteroides and other Leuconostoc spp. take dominance. In the third phase, various Lactobacillus species, including L. brevis and L. plantarum, ferment any remaining sugars, further lowering the pH ⁴. Properly cured sauerkraut is sufficiently acidic to prevent a favorable environment for the growth of Clostridium botulinum, the toxins of which cause botulism ⁵.

Sauerkraut contains a large quantity of lactic acid; vitamins C and minerals and has few calories (about 17 Cal/100g). Sauerkraut was one of the major foods in seafaring due to its high vitamin content and was used to counteract scurvy ⁶.

in Germany, approximately 200 000 tons of cabbage are processed into sauerkraut. Between 1975 and 1980, the per capita use of sauerkraut in Germany stayed constant at 2.0 to 2.1 kg per year.3,4 Sauerkraut is also very popular in the Untied States and France, where it is also known as “German Kraut” or “Cassoulet.”

Figure 1. Sauerkraut

Sauerkraut nutrition facts

Table 1. Sauerkraut nutrition facts

Ingredients: CABBAGE, WATER, SALT, LACTIC ACID.

[Source: United States Department of Agriculture Agricultural Research Service ⁷]

Sauerkraut health benefits

Popular papers on healthy lifestyle suggest that regular sauerkraut consumption can contribute to a healthy digestive flora. The authors of these papers claim that adding foods like sauerkraut or kimchi to the diet is beneficial as they may deliver probiotics into the gastrointestinal system ⁸. However, empirical studies towards this topic are widespread and focus on a variety of aspects. While a number of articles on the analysis of sauerkraut are available, the impact on human health is covered by only a minority of the articles found. Some main points of investigation can be identified as described below.

Although sauerkraut has a variety of claimed beneficial health effects, they need to be interpreted with caution as it can also cause some unwanted or even allergic reactions, in particular in high-risk populations, such as depressive or allergic patients ⁹. Future research in this area should include clinical studies investigating further effects in more detail, including an appropriate sample size as well as the assessment of possible adverse events of sauerkraut.

Table 2. Publications on Sauerkraut Dealing With Human Health

First author	Year	Country	Study type	Subject	Outcome parameter
Gehlen	1932	Germany	Lab research	Food itself	Pharmacological effect
Knapp	1953	Germany	In vitro	Bacteria	Antibacterial effect
Doeglas	1968	Netherlands	Clinical study	Humans	Urticarial reaction
Gillooly	1983	South Africa	Clinical study	Humans	Iron absorption
Reele	1985		In vivo	Humans	Sorbitol-induced diarrheal illness model
Groenen	1988	Netherlands	Lab research	Food itself	Alkylating activity
Sweet	1995	United States	Survey	Humans	Psychiatric patients’ frequency of consumption
Walker	1996	Canada	Lab research	Food itself	MAOI diet by determining the tyramine content of a variety of untested and “controversial” foods
Tantcheva-Poór	1999	Germany	Survey	Humans	Sources of cytochromes
Danchin	1999	France	Clinical study	Food itself	Test comparative effects between 2 types of sauerkraut
Diehl	1999	Germany	Survey	Humans	Food preference in this age group
Saloheimo	2005	Finland	Lab research	Food itself	Scurvy prevention
Hasnip	2007	United Kingdom	Survey	Food itself	In-house survey of fermented foods and beverages sold in the UK
Penas	2010	Spain	Lab research	Food itself	Storage effect
Wang	2011	China	Clinical study	Humans	Lifestyle risk factors
Szaefer	2012	Poland	In vitro	Food itself	Effect of raw cabbage and sauerkraut juices on the activity and expression of CYP1A1, 1A2, 1B1 and 2
Szaefer	2012	Poland	In vitro	Food itself	Investigate the effect of cabbage and sauerkraut juices of different origin
Penas	2012	Spain	Lab research	Food itself	Production of selenium-enriched sauerkraut

[Source ⁹]

Sauerkraut and Cancer

Cancer protection is one of the major goals of almost every healthcare system worldwide. Experiments found that high levels of glucosinolates, ascorbigen, and ascorbic acid decrease DNA damage and cell mutation rate in cancer patients, and sauerkraut is known to have a high content of these compounds. However, the level of concentration strongly depends on the fermentation conditions of the cabbage ¹⁰. According to Martinez-Villaluenga ¹¹, producing cabbage at low-salt concentration improved ascorbigen content, with the highest concentration being observed in low-sodium (0.5% NaCl) sauerkraut produced from cabbage cultivated in winter using natural fermentation. Ascorbic acid content, on the other hand, was found to be higher in cabbage cultivated in summer, with fermentation reducing the content. This is supported by the studies of Penas and Szaefer ¹². However, inhibition of enzymatic markers in the liver might not be seen as an indicator for anticarcinogenic activity, even if markers in the kidney show enhanced activity, which might be due to interaction effects. Thus, the evidence base of sauerkraut for cancer currently seems to be inconclusive. This is even more questionable when considering the results of Wang et al, ¹³ who found sauerkraut to be a risk factor for cancer. Apart from cancer-related aspects, different types of fermentation processes might also explain the results of the CASS-CHOU study on mesenteric angina, which also found significant differences between the sauerkraut products in that study ¹⁴.

Sauerkraut and Allergic Reactions

Sauerkraut not only has high content of tyramine and glucosinolates but also shows high concentrations of histamine. Histamine in food has been proposed to be a major cause of food intolerance ⁹. Allergic reactions go along with a release of histamine; therefore, histamine in food might contribute to allergic symptoms, although the food itself is not a cause of the allergic reaction. The additional histamine load has to be considered, especially, for instance in the high season for people who suffer from hay fever. This is supported by a recent study by Wöhrl et. al ¹⁵ in healthy volunteers, who found that oral provocation with liquid histamine might result in symptoms like tachycardia, mild hypotension, sneezing, itching of the nose, and rhinorrhea but also and more often in diarrhea or flatulence, headache, or pruritus. Thus, high intake of sauerkraut in sensitive people might result in similar reactions.

The study by Doeglas et. al ¹⁶ revealed false-positive scratch test results due to urticarial reactions caused by high histamine content and therefore must also be taken into consideration. Again, preparation of sauerkraut also influences its level of histamine content. A very early study by Taylor ¹⁷ in 50 samples of sauerkraut found the histamine concentration to range between 0.91 mg/100 g and 13.0 mg/100 g. The review by Kalac ¹⁸ revealed mean histamine concentrations between 0.6 mg/100 g and 5.6 mg/100 g. Their own experiments found histamine levels below 0.2 mg/100 g in 44% of their samples and above 1 mg/100 g in only 19% of the samples. Looking at the very early studies of Gehlen et al ¹⁹ and Reele et al ²⁰, one has to consider that the effect of sauerkraut on the digestive tract of cats and frogs cannot directly be transferred to humans and that the effect of the use of the juice can be different from the effect of the use of the whole sauerkraut, including the fibers. The main enzyme for metabolism of ingested histamine is diamine oxidase (DAO), which plays a major role in amine degradation in the human body and is mainly produced in the epithelium of the large intestine. However, only limited evidence is available on the interaction of diamine oxidase and histamine degradation. Current work by Naila et al ²¹ used a tuna soup model with a constant concentration of histamine (500 mg/L) and DAO enzyme (2534 units/L) to predict the rate and amount of histamine degradation by DAO. They suggested using this model for food with similar characteristics. In this respect, sauerkraut juice might be one promising option for further basic research. Furthermore, it is unclear whether vitamins, especially vitamin B6 in sauerkraut, might support the production of DAO. The production of DAO could also be increased by improved gut function due to the fibers, minerals, and vitamins in sauerkraut—and may even benefit allergic patients.

According to personal clinical experience, regular intake of small doses of sauerkraut—7 g to 10 g (or about 1 tablespoon) daily—has a very good effect on many patients’ gastrointestinal tract. They report better digestion and less constipation. Allergic problems have not been observed. However, clinical studies are needed to support this anecdotal experience.

To evaluate the effect on the gut, further research would have to consider the amount and regularity of the intake of sauerkraut and its effect on digestive markers and clinical symptoms, including a possible benefit for weight control due to the low content of calories in connection with high content of fibers and vitamins ²².

 

The Interaction of Sauerkraut With Monoamine Oxidase Inhibitors

Monoamine oxidase inhibitors (MAOIs) inhibit the activity of the monoamine oxidase enzyme family and therefore are prescribed for the treatment of depression, anxiety disorders, obsessive compulsive disorders, and Parkinson’s disease. There is evidence that MAOIs are likely to interact with complementary remedies or food supplements like St John’s wort ²³ or gingko ²⁴. Due to its dangerously high concentrations of tyramine, sauerkraut appears on MAOI diet–restricted food lists ²⁵. However, the concentration of tyramine as well as other biogenic amines shows a broad variation in samples of sauerkraut. A very early study by Kalac et al ²⁶ found variations of mean tyramine concentrations in different studies between 25 mg/kg and 89 mg/kg. In the authors’ own experiments, they found tyramine concentrations of six Czech manufacturers between 107 mg/kg and 436 mg/kg, with the lowest concentrations found in household preparations of sauerkraut. These results are underpinned by another study by Kalac et al ²⁷, which found significant lower biogenic amine levels in sauerkraut being isolated from bacteria from shredding machines, transporters, and silos. Moreover, sauerkraut inoculated with L plantarum or Microsil also showed significantly lower concentrations of tyramine. Finally, the same working group found a relationship between storage time and tyramine concentration with significantly higher concentrations of tyramine in long-stored sauerkraut ¹⁸. Thus, dietary restrictions for sauerkraut have to take type, preparation, and storage time of sauerkraut into account.

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