[Kim Jaeho's Life Story]<194> The Pitfall of the All-Powerful Fermented Foods

Recently, French researchers announced a study suggesting that the reason for the low number of deaths from the novel coronavirus disease (COVID-19) in South Korea and Germany is due to dietary habits that mainly include fermented foods such as Kimchi. During the 2002-2003 outbreak of Severe Acute Respiratory Syndrome (SARS), there was also a claim that the relatively low human casualties in South Korea were because of Kimchi. South Korea's Kimchi exports increased by 28.2%, from 23,000 tons in 2015 to 30,000 tons in 2019, and in the first half of this year, exports reached 20,000 tons, which is a 37.9% increase compared to the same period last year, possibly due to the impact of COVID-19.

Fermentation refers to a metabolic process in which microorganisms such as yeast or bacteria obtain the necessary energy by breaking down carbohydrates without using oxygen. When the substances produced during this breakdown are beneficial to humans, it is called fermentation; if they cause harm such as bad odors or toxicity, it is called spoilage. Scientifically, fermentation and spoilage are the same. Fermentation occurs extensively in the gastrointestinal tracts of humans and animals, and independently of microorganisms, muscles of mammals produce energy through fermentation that creates lactic acid when oxygen supply is insufficient during intense exercise.

The substances produced during fermentation can be classified into three types. First, lactic acid fermentation, where yeast or bacteria convert carbohydrates into lactic acid, as in Kimchi, pickles, and yogurt; second, ethanol fermentation, where yeast converts carbohydrates in fruits or grains into ethyl alcohol (ethanol); and third, acetic acid fermentation, where carbohydrates are converted into acetic acid or butyric acid, producing gases such as carbon dioxide, hydrogen, and methane.

Fermentation is a part of the ecosystem cycle. Plants use solar energy to produce carbohydrates, proteins, and fats to grow, while humans, animals, and microorganisms that cannot perform photosynthesis survive and grow by utilizing carbohydrates, proteins, and fats contained in plants or other animals, breaking them down to obtain necessary energy. Among the ways microorganisms obtain energy, the special form of breaking down carbohydrates without oxygen to use energy is specifically called fermentation.

Humans have long used fermentation in making food and beverages. Lactic acid fermentation was used to preserve foods such as Kimchi, pickles, and yogurt, and fermentation was also widely used to produce alcoholic beverages like wine and beer.

Fermentation used in food processing involves fermenting carbohydrates with microorganisms such as yeast or bacteria in the absence of oxygen to produce ethyl alcohol or lactic acid. The carbohydrates to be fermented include legumes, grains, fruits, vegetables, honey, tea, dairy products, fish, and meat. The fermented foods produced include alcoholic beverages such as wine, beer, and cider, dairy products like yogurt, bread, Kimchi, vinegar, cheese, and more.

Among fermented foods, ethanol contained in alcoholic beverages is classified as a Group 1 carcinogen by the International Agency for Research on Cancer (IARC) under the World Health Organization (WHO) and is a very harmful substance. However, fermented foods containing lactic acid produced by various bacteria called lactic acid bacteria have many beneficial effects. When people say fermented foods are good for health, they usually refer to these lactic acid fermented foods.

Lactic acid fermented foods act as natural preservatives, so lactic acid fermentation was used as a method to preserve food and beverages before refrigerators existed. Carbohydrate fermentation is natural and beneficial within foods, increasing probiotics known as good bacteria, enhancing the activity of intestinal bacteria. It helps digestion and absorption of food, aids the availability and synthesis of nutrients including vitamins and minerals, and also improves immune function.

Recently, as the advantages of fermented foods have been highlighted, interest in fermented foods has increased, and it is easy to think of fermented foods as a cure-all. However, eating more fermented foods is not necessarily better. Although fermented foods have many benefits, there are also negative aspects, so it is advisable to consume them in moderation. Eating too much of any good food can cause nutritional imbalances, making it difficult to expect fundamentally good outcomes.

Among the negative aspects, concerns have been raised about cancers such as stomach and esophageal cancer. The International Agency for Research on Cancer (IARC) classifies pickled foods as Group 2 carcinogens, and studies have shown that fermented foods contain urethane, a carcinogen. Research also indicates that consuming large amounts of fermented soybean products significantly increases the risk of stomach cancer, and regularly eating pickled vegetables doubles the risk of esophageal squamous cell carcinoma. Additionally, temporary side effects such as gas and bloating, headaches, histamine intolerance, and antibiotic resistance have been pointed out.

Kim Jae-ho, Independent Researcher