From grandma’s cabbage to trendy kimchi: what fermentation really offers to the gut

The interest in them is no longer solely tied to the desire to preserve crops. Fermented products have become a popular part of a healthy diet, especially when it comes to gut health. But is regular sauerkraut truly beneficial for digestion, and is it necessary to buy expensive products with live bacteria?

Fermentation is a process in which microorganisms transform substances contained in products.

When pickling cabbage and other vegetables, lactic acid bacteria perform the main role. They break down sugars and produce lactic acid. It is this acid that gives the characteristic sour taste, and properly prepared vegetables can be stored longer than fresh ones.

For such fermentation, it is not necessary to buy special starters. The required microorganisms are usually present on the surface of the vegetables themselves. However, it is important to create suitable conditions: use the right amount of salt, maintain the proper temperature, and prevent the vegetables from being in contact with air for too long.

Incidentally, pickling and quick pickling with vinegar are not the same thing. In the latter case, acid is added immediately, and natural fermentation may not occur at all.

A vast number of microorganisms live in the human intestine. Their community is known as the gut microbiota.

Diet affects its composition, and fermented foods hold special interest for researchers.

A 2021 Stanford University study involved 36 healthy adults. Scientists found that those who increased their consumption of fermented foods over ten weeks experienced an increase in gut bacterial diversity and a reduction in certain inflammation markers. However, it’s important to note that the participants consumed various products, including yogurt, kefir, kimchi, and fermented vegetables. The study does not prove that sauerkraut specifically has this effect on everyone.

Fermented vegetables also have a more straightforward advantage—they remain vegetables. For example, cabbage contains fiber, which is important for proper gut function.

Therefore, it’s better to consider sauerkraut and kimchi as additions to a varied diet rather than a remedy for digestive issues.

Not necessarily.

According to the International Scientific Association for Probiotics and Prebiotics (ISAPP), not every fermented product contains live microorganisms at the time of consumption. For example, live cultures may die after pasteurization or prolonged heating.

In addition, the term “probiotic” is used in science to refer to certain microorganisms whose benefits have been confirmed by research. Simply having live bacteria does not yet make a product a proven probiotic. Therefore, one should not choose sauerkraut solely based on the exaggerated claims on the packaging.

It is better to pay attention to the ingredients, preparation method, and storage conditions.

In October, this is one of the most affordable options for home fermentation. Only two ingredients are needed, and the finished cabbage can be served with potatoes or meat or used to make borscht.

Ingredients:

• 1 kg of head cabbage;

• about 22 grams of iodine- and additive-free salt for pickling.

How to prepare:

1. Remove any damaged outer leaves, wash the cabbage head, cut off the stem, and thinly slice the cabbage.
2. Add the salt and mix thoroughly with clean hands. Then crush the cabbage until it begins to release juice.
3. Place it tightly in a clean glass jar or suitable fermentation container. Press the vegetables down so that the brine produced covers the cabbage. Place an appropriate clean weight on top, leaving space for the juice that forms.
4. Cover the container to protect its contents from contamination and allow fermentation gases to escape. It is best to use a special fermentation lid.

According to the recommendations of the U.S. National Center for Home Preservation, at a temperature of around 21–24 °C, complete fermentation of cabbage usually takes three to four weeks. In a cooler environment, the process takes longer. Throughout this time, the cabbage must remain submerged in the brine. After fermentation is complete, it is stored in the refrigerator.

Important note: do not reduce the amount of salt at random. During fermentation, it is needed not only for flavor but also to ensure the process proceeds properly.

Kimchi is a traditional Korean side dish made from fermented vegetables. Unlike regular sauerkraut, it has a spicier taste with garlic and chili peppers.

A simple version based on a recipe from Oregon State University is suitable for beginners.

Ingredients:

• 900 grams of bok choy;

• 110 grams of daikon radish;

• 2½ tablespoons of salt for pickling without additives;

• 2 scallions;

• 3 cloves of garlic;

• 2 teaspoons of finely chopped hot red pepper;

• 2 teaspoons of sugar.

Optionally, you can add 1 teaspoon of finely grated ginger.

How to prepare:

1. Rinse the bok choy and cut it into pieces about 2–3 cm long. Sprinkle two tablespoons of salt over it, mix, and let it sit for several hours until the volume of the leaves significantly decreases.
2. Then rinse it thoroughly under a strainer and let the water drain out without squeezing the leaves.
3. Cut the daikon into thin strips, the green onions into small pieces, and mince the garlic and chili peppers.
4. Combine the vegetables with the cabbage, add sugar and the remaining half tablespoon of salt. Mix well.
5. Transfer the mixture into a clean one-liter jar, leaving some space at the top, and cover it with a lid that is not airtight. Make sure the vegetables are not above the liquid that has formed.

According to the Oregon State University Extension recipe, this preservation is left at room temperature for one to four days before being stored in the refrigerator. The duration depends on the temperature: fermentation proceeds faster in warmer conditions.

Kimchi is convenient to serve as a small side dish with rice, meat, or other familiar dishes.

The most frequent mistake is altering the proportions at one's own discretion.

• Salt plays a role in creating conditions that allow the desired microorganisms to grow. If its amount is significantly reduced or the recipe is changed arbitrarily, the result can be an unsuccessful and unsafe product.
• Another error is leaving the vegetables above the brine. Exposure to air increases the risk of unwanted microorganisms and mold forming.

It is also important to maintain clean utensils and follow the recommended temperature. Do not place the jar on a hot radiator to speed up the process. If mold, excessive slime, or an unpleasant rotten smell appears, the preserved vegetables must be discarded. You should never eat suspicious vegetables to test their safety.

And remember that home fermentation alone does not make the product suitable for long-term storage in a warm cupboard. After preparation, the vegetables need to be stored under the conditions specified in the recipe.

There is no specific mandatory amount of fermented vegetables to consume every day.

At first, a small addition to your regular meals is sufficient. For example, a few tablespoons of pickled cabbage with potatoes or a small portion of kimchi with rice.

Very large portions do not guarantee greater benefits. Additionally, fermented vegetables often contain a lot of salt, and for some people, unfamiliar foods may cause bloating and discomfort. Therefore, it is better to increase the amount gradually, depending on tolerance.

And most importantly: there is no need to replace fresh vegetables, grains, and other fiber sources with such prepared foods.

Fermentation is not a magical way to improve gut health, but rather another option to make daily meals more varied. Our grandmothers made sauerkraut mainly for flavor and to preserve their harvest. Today, this practice has been supplemented by interest in gut microbiota and live cultures. But you can still start with the most ordinary cabbage, salt, and a clean jar.