Why We Should All Eat Kimchi and Other Korean Fermented Foods

Why We Should All Eat Kimchi and Other Korean Fermented Foods

A recent one fermentation A journal study examines various traditional Korean fermented foods for their biological functions, production and future contribution to global well-being.

Learn: Fermented foods from Korea and their functionalities. Photo credit: PAPA WOR / Shutterstock.com

Common Korean fermented foods

Food is fermented through microbial biochemical reactions that synthesize or break down organic substances to produce new products, including fatty acids, organic acids, and vitamins. These microorganisms can also act as probiotics, further enhancing the health benefits of fermented foods.

The most common Korean fermented foods are kimchi, jang, jeotgal and vinegar. Kimchi, for example, considered Korea's fermented food, was once made from various vegetables, including cabbage, sweet potatoes, eggplant, cabbage, radish, mustard greens, turnips and lettuce.

Although soybeans are the main ingredient for jang, they are often accompanied by grains, peppers and salt. In comparison, jeotgal, which is also used to enhance the flavor of foods such as jang, is a fermented fish product; Shrimp, molluscs, squid, squid and crustaceans can also be used to make this product.

Vinegar, the oldest fermented food product used in Korea, is typically produced through alcohol fermentation, followed by acetic fermentation, which is achieved through the inoculation of acetic acid bacteria. Like other countries around the world, Korean cuisine incorporates vinegar into various foods to create a refreshing and sour taste.

hypertension

Most fermented food products commonly incorporated into Korean dishes have historically been used for their health benefits. Despite the high salt content of these food products, particularly jang, limited evidence has linked jang consumption to high blood pressure.

Instead, several studies have shown that some Korean fermented food products may be associated with blood pressure-lowering health benefits. Doenjang, for example, is made through a long fermentation product that has contributed to its ability to lower blood pressure (BP) and control the renin-angiotensin system (RAS).

Cheonggukjang also helps regulate blood pressure. In comparison, consumption of gochujang suppresses thrombolysis and inhibits angiotensin-converting enzyme (ACE) activity and platelet aggregation.

Evidence from a previous survey suggested that people who regularly consumed kimchi also had relatively lower blood pressure; However, further studies are needed.

obesity

Several studies have examined the impact of kimchi on body weight, with various factors including fermentation level and ingredients contributing to this positive effect. Kimchi with red pepper, for example, appears to reduce perinephric fat deposits and body weight and promote fat loss and energy expenditure.

Previous studies have also reported reduced expression of obesity-related genes in overweight individuals who consume kimchi. In addition, kimchi consumption also reduced markers of metabolic diseases such as insulin, high-density lipoprotein cholesterol (HDL-C), BP and C-reactive protein (CRP) in these individuals.

Depending on the fermentation time of doenjang, its protective effects against metabolic disease-associated risk factors vary. Still, Doenjang has been shown to be highly effective against obesity, as shown by computed tomography (CT) images and reduced expression of genes linked to fat cell development.

Several studies have also confirmed the anti-obesity effects of fermented and non-fermented gochujang. In addition, gochujang also improves lipid profiles and reduces visceral fat levels, while cheonggukjang improves lipid metabolism and shows anti-obesity effects.

Persimmon vinegar has been shown to be effective in regulating blood sugar levels, body weight, and improving fat metabolism. These effects are likely due to the high organic acid content in this product, some of which include acetic, citric and malic acids.

Diabetes mellitus

The metabolites and active ingredients contained in kimchi are likely to support the effective treatment of diabetes. In fact, in vivo results have shown that four weeks of kimchi consumption successfully reduced blood sugar levels in an animal model of type 2 diabetes.

When obese people consume gochujang, their insulin sensitivity generally improves, which regulates their glucose levels. In addition, Cheonggukjang has a high fiber content with a low glycemic index, making it suitable for controlling blood sugar levels.

Cheonggukjang also contains a trypsin inhibitor, which increases insulin sensitivity and secretion. In clinical settings, consuming Cheonggukjang for eight weeks has been shown to reduce fasting blood glucose levels, low-density lipoprotein cholesterol (LDL-C), and total cholesterol levels. This product also suppresses a-glucosidase activity, thereby improving insulin resistance.

Cucumber vinegar has also been shown to regulate insulin levels.

Lipid profile

Kimchi inhibits lipid production in blood vessels. Additionally, consuming aged kimchi lowers pro-inflammatory cytokine levels, which are often linked to atherosclerosis.

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In obese individuals, aged kimchi has been shown to lower blood pressure, fasting blood sugar, and body fat percentage, all of which are risk factors for metabolic syndrome. In healthy individuals, consumption of cabbage kimchi has been associated with reduced blood LDL-C/HDL-C ratio, triglycerides (TG), and atherosclerosis index. Additionally, consuming fresh and fermented kimchi may improve fat metabolism, obesity, and inflammation in prediabetics.

Doenjang reduces the risk of cardiovascular disease and atherosclerosis by lowering LDL-C, total cholesterol and very low-density lipoprotein (VLDL)-C levels and inhibiting thrombin production and lipid synthesis and delaying fibrin coagulation. In addition, this food product also suppresses thrombolysis and platelet aggregation.

Fermented gochujang has a positive effect on lipid metabolism and has been shown to reduce hyperlipidemia, LDL-C, total cholesterol levels and obesity.

Protease present in Cheonggukjang suppresses cholesterol synthesis and has antithrombotic effects. Cheonggukang is also rich in indigestible saccharides and fiber, which reduce the absorption of total cholesterol and triglycerides and promote fecal lipid excretion, thereby helping to prevent atherosclerosis.

Clinically, consumption of Cheonggukjang had an anti-atherosclerosis effect in obese individuals. Cheonggukjang also appears to reduce the index protein associated with atherosclerosis.

Gastrointestinal effects

Microorganisms in kimchi act as probiotics, which have a positive effect on intestinal health. Lactic acid bacteria in kimchi lower the pH value in the intestine and inhibit the absorption of intestinal toxins and the proliferation of harmful bacteria. In particular, kimchi consumption is often associated with positive effects in patients with irritable bowel syndrome (IBS).

Doenjang fermentation produces vitamin B12 and K2. The Bacillus sp contained in Cheonggukjang improves overall intestinal health, facilitates intestinal movement and suppresses harmful bacteria. Regular consumption of Cheonggukjang relieves the symptoms of inflammatory colitis.

Cancer

Kimchi has anticancer and antimutagenic effects against known carcinogens, with fermented kimchi being associated with higher levels of antimutagenic effects. Cancer Preventive Kimchi (CPK) reduces the risk of inflammation and stomach cancer and relieves certain cancer symptoms.

Ganjang is also associated with certain anti-cancer properties. When sesame seeds are added to ganjang, their anti-cancer properties are enhanced. In addition, ganjang older than 15 years can significantly increase natural killer (NK) cell activity and spleen cell proliferation.

Meju, the raw material used to prepare doenjang, is susceptible to aflatoxin-producing fungi. Prolonged exposure to aflatoxin increases the risk of developing cancer.

Doenjang that is more than a year old harbors microorganisms that limit the production of aflatoxin. Prolonged fermentation time increases the anti-metastasis and anti-cancer effects of doenjang. In addition, Doenjang has tumor-suppressing and liver detoxifying effects.

Gochujang also has anti-cancer and anti-metastasis properties. The anti-cancer benefits of this food product increase with longer fermentation times, making these effects of traditional gochujang more pronounced.

Bay salt used in the preparation of jeotgal has been attributed to its antimutagenic activity. Unfermented jeotgal also shows antimutagenic activity.

The antioxidant effect of Cheonggukjang is proportional to the content of isoflavones and polyphenols.

The immune system

Consuming kimchi in sufficient quantities can reduce the severity of allergic rhinitis, atopic dermatitis and asthma. Similarly, doenjang boosts immunity and is associated with antioxidant, anti-inflammatory and immunomodulatory activities.

Cheonggukjang has immunomodulatory properties, improves immunological functions and relieves allergies. Likewise, Jeotgal has anti-inflammatory properties and broader anti-allergic effects.

Oxidative stress and aging

Ripened kimchi is composed of several antioxidant substances, including vitamins C and A, lactic acid bacteria and various metabolites, all of which help break down free radicals. When mustard leaves are used to prepare kimchi, anti-aging effects are achieved through its ability to reduce the production of free radicals in the brain.

Cheonggukjang is also composed of several compounds that can reduce oxidative stress and inflammation, including isoflavones, glycans, peptides, fiber and microorganisms.

Reference:

• Jung, S., Chae, S., & Shin, D. (2022). Fermentierte Lebensmittel aus Korea und ihre Funktionalitäten. Fermentation. doi:10.3390/fermentation8110645

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