For many millennia, fermented foods have been an important component of the human diet. Fermentation has been used since the Bronze Age to preserve food. Naturally occurring bacteria (e.g., lactobacilli) and yeasts break down the carbohydrates in the food. In that process, lactic acid, carbon dioxide and a large number of bioactive substances are formed which prevent other harmful microorganisms from growing.

Since industrialization in the 19th century, many new methods have been developed for processing and preserving food. Drinking water also began to be treated to counteract microbial contamination back then. These things combined with the introduction of antibiotics and our modern lifestyle of good hygiene and small families has contributed to us being exposed to fewer microbes today than before.

Despite the obviously positive effect on public health of better hygiene both in terms of food and lifestyle, there seems to be unforeseen negative effects of the lower exposure to microbes. While deaths from infectious diseases have decreased, the number of immunological, metabolic and other lifestyle-related diseases such as asthma, allergies, diabetes and cardiovascular disease is increasing. Our intestinal flora is needed to train and strengthen our immune system and about 70% of the immune system is located in the gastrointestinal tract. The lack of living microorganisms in our diet may contribute to the development of these diseases.

A group of American researchers has recently published a progress report on the benefits of fermented foods. Researchers suggest that we should reintroduce health-promoting microorganisms into our daily diet to combat disease.

What evidence is there today that fermented foods are useful?

Most studies have been done on yogurt, both large epidemiological studies but also a large number of prospective, randomized case-control studies. There are only a few randomized case-control studies with sauerkraut, kimchi, kefir and sourdough bread, so it is more difficult to comment on the health effects of these foods.

Regular consumption of yogurt is associated with lower body weight and waist size, lower morbidity in diabetes (type 2) and cardiovascular disease. Yogurt with live bacterial cultures is rich in minerals and vitamins, such as calcium, potassium, riboflavin and vitamin B12. There are studies that show a positive effect on bone density and the barrier function of the intestinal mucosa. In addition, the bacteria in yogurt break down the milk sugar lactose. Lactose is found in all milk, not only in cow’s milk but also in goat’s and sheep’s milk. Many people tolerate buttermilk, yoghurt and other fermented milk products even if they are lactose intolerant.

Research on the role of the intestinal flora for our health indicates that regular consumption of safe, living microbes increases our health. To maintain a healthy intestinal flora with a variety of microbes, we not only need to eat a varied diet that contains a lot of fiber from the plant kingdom, but also fermented foods. So far, there are no guidelines or dietary recommendations to ensure this but here’s a list for those of you who want to try. I make both milk and water kefir at home, sometimes sauerkraut as well.

Examples of foods that are fermented by different methods:

Lactic acid fermentation
Buttermilk, yoghurt, crème fraiche, sour cream, cheese, sauerkraut, kimchi, fish sauce, salami, olives, herring

Alcohol fermentation
Beer, wine, cider, sake

Molds
mold cheeses, tempeh

Both fungal and bacterial fermentation
Kefir, kombucha

Honey is also fermented in bees’ stomachs and contains many different strains of lactobacilli and bifodobacteria.

This is a guest post. Any opinions expressed are the writer’s own.