Kimchi and its antiobesity and anticancer functions

Abstract

Kimchi is a Korean traditional vegetable fermented food with lactic acid bacteria (LAB). Fermented kimchi contains live LAB (probiotics), dietary fibers (prebiotics) and dead LAB and fermented metabolites (postbiotics), and it may have various health benefits. The taste and functionalities of kimchi are dependent on its main ingredients and subingredients, fermentation conditions, LAB in the fermentation, etc. There are many types of kimchi, but Baechu kimchi is the most popular and commonly used kimchi in Korea. Baechu kimchi is prepared by LAB fermentation of Baechu cabbage mixed with other subingredients such as radish, green onion, red pepper powder, garlic, ginger and fermented small sea fishes. Kimchi contains high levels of vitamins, minerals, dietary fibers and other functional components and fermented metabolites. Various studies have reported on kimchi and its antimutagenic and anticancer, antioxidative and antiaging, antiatherosclerotic, antidiabetic, antiobesity, and anti-inflammatory effects. Fermented kimchi contains high levels of LAB (10^8–9 CFU/g) and LAB also contribute functionalities to kimchi. We will discuss the process of manufacturing kimchi, fermentation of kimchi and related microorganisms. Though it briefly discuss on the general functionalities of kimchi, we will focus on the history and functions of the antiobesity, anticancer, and anti-inflammatory effects of kimchi in detail with better taste and preservation period. To increase the antiobesity and anticancer functions of kimchi we will introduce kimchi recipes, salt kinds, other added ingredients, etc. It was finally discussed on postbiotics in kimchi and their health benefits.

Introduction

Salted vegetables (e.g., Jeo in Chinese character), a type of macerated vegetable were consumed 3C or 4C, AD in Korea. Jeo is regarded as a precursor of kimchi and is estimated to have been consumed in the Gojoseon era (1C, BC) during the Iron Age. Thus, kimchi originated at least 2000 years ago [1]. Kimchi is a Korean fermented vegetable food and a side dish served at every meal among Koreans. Korean meals are organized around a table, rice is the main food, there are other side dishes, such as kimchi, soy sauce, and soup, and the number of side dishes increases depending on the social class or wealth, such as 3, 5, 7, 9, and 12 chubs, depending on the number of other side dishes. There are 161–187 types of kimchi, but among them, Baechu cabbage kimchi accounts for more than 70% of kimchi; therefore, kimchi usually refers to Baechu kimchi [2].

Baechu kimchi is a lactic acid fermented food made with Baechu cabbage as its main ingredient; it is pickled in salt, drained, and seasoned with natural lactic acid bacteria. Fermentation is important, and the taste and health functionality of kimchi can be changed depending on the ingredients and amounts, the kimchi manufacturing method, and the storage method, such as the use of a kimchi refrigerator. Baechu cabbage and radish, the main ingredients of kimchi, are cruciferous vegetables, seasonings such as red pepper powder, garlic, ginger, and green onion are useful troves of phytochemicals, and fermentation with lactic acid bacteria (LAB), which are probiotics, and dietary fiber from vegetables, which becomes a raw material as prebiotics. After salting the cabbage, it is fermented with approximately 10⁴ CFU/g of lactic acid bacteria naturally present in the cabbage at home, and LAB starters (10⁶ CFU/g) can be added in the industry. After fermentation of kimchi is completed, the number of lactic acid bacteria increases to 10⁹ CFU/g, becoming a probiotic food. Even after fermentation, the number of dead cells increases as much as the number of viable cells, and heat-treated kimchi such as kimchi stew or kimchi pancakes contain dead cells. Therefore, kimchi has probiotics (live bacteria), prebiotics, and postbiotics (dead bacteria), and the bioactive compounds of fermentation products (organic acids, vitamins, minerals, flavor compounds, phytochemicals, etc.) produced during kimchi fermentation are mixed with the above components and play important roles in health functionality [3].

Kimchi has various health benefits such as antioxidant, antiaging, anticancer, antiobesity, and immune enhancing effects due to its nutrients, bioactive compounds, and fermentation components. Additionally, the kimchi LAB derived from kimchi themselves have health-improving effects. Most kimchi is eaten at home, and especially before winter, it is held annually to put a large amount of kimchi to eat in winter through an event called Kimjang. The history, types, manufacturing methods, fermentation, functionality, etc. of kimchi were described in several places [2,3,4,5,6,7]. About 50% of consumers buy kimchi manufactured by industrial companies, but Koreans prefer kimchi made at home. Heterofermentative LAB improve taste, and the LAB used in kimchi produced by industrial companies these days are heterofermentors of Leuconostoc, Weissella, and Lactobacillus [8]. To improve taste and functionality, starters with good functionality are also used. The use of starters not only improves the taste of kimchi, but also improves its marketability and various customized functions. In this paper, we briefly introduce the processing and preparation method and kimchi fermentation and LAB in kimchi, and explains the antiobesity and anticancer effects in detail among the functionalities of kimchi.

Preparation methods for kimchi

Standardized kimchi recipe

The standardized recipe for Baechu kimchi which is representative Korean kimchi is as follows. The standardized composition of baechu kimchi recipe from scientific papers, cookbooks, recipes from kimchi companies, family traditions, etc. [9,10,11] is as follows: brined baechu cabbage (100%) is mixed with 2.5 ± 0.3% or 3.5 ± 0.8% red pepper powder, 1.4 ± 0.4% crushed garlic, 0.6 ± 0.3% crushed ginger, 1.0 ± 0.3% sugar, 13.0 ± 7.0% sliced radish, 2.0 ± 0.5% cut green onion, 2.2 ± 1.6% anchovy fermented juice, and a final salt content of 2.5–2.7% (1.5–3.5%). Various kinds of jeotgals such as salted and fermented fish and shellfish could be used, however, anchovy fermented juice and salted small shrimp were the main jeotgals used to increase the taste of kimchi. Cho et al. [10] indicated that various other subingredients could be added such as mustard leaf, water dropwort, shredded red pepper, carrot, pear, apple, chestnut, oyster, dried pollack, cutlass fish, glutinous rice paste, and sesame seeds according to preferences related to taste, family tradition, and availability in the region.

Standardized processing and preparation methods

Preparing kimchi differs depending on the ingredients used, family preferences, regional customs, etc. The process consists of preparation and pretreatment of the raw ingredients, mixing the ingredients, packaging, and fermentation. Pretreatments of the raw ingredients included grading, washing, and cutting. Other ingredients are also graded, washed, cut, sliced, or chopped for proper mixing.

The processing and preparation of kimchi are shown in Fig. 1. Beachu is prepared by two major methods. One is tongbaechu kimchi, a more common kimchi preparation using whole cabbage (tongbaechu), preserved for the long-term winter season which is typical of kimchi prepared at home for kimjang. The other method involved cutting of matbaechu kimchi (cut the cabbage 3–5 cm in length). In preparation for tongbaechu kimchi, baechu is cut lengthwise into 2 or 4 parts from the bottom to the cabbage head. The cut cabbages are treated with dry salt (usually bittern-reduced solar salt) or with 10% brine for 10 h. The brined cabbage is rinsed to remove excess salt and then allowed to drain for 3 h. A premixture of spices and other subingredients, according to the recipe, is packed between the layers of the cabbage leaves. The stuffed cabbage is wrapped with outer leaves, which removes the oxygen, and then packed into containers (traditionally in clay pots, called Ongi). Ongi may allow for facultative anaerobic conditions for LAB fermentation.

Fig. 1

Standardized diagram for the preparation of Baechu cabbage kimchi. ¹Cutting methods: Tongbaechu kimchi (2 or 4 pieces of whole cabbage), Matbaechu kimchi (3–5 cm cut)

Kimchi fermentation and LAB in kimchi

Kimchi fermentation occurs naturally; however, active starters can be added in industry. The main endogenous microorganisms, LAB, and ferment sugars such as glucose, fructose, etc. are found in cabbage and subingredients. Various chemical, physical, and biological factors may also contribute directly to the growth of LAB and to the extent of fermentation. Several environmental factors influence kimchi fermentation such as type of microorganisms (MOs), salt concentration, fermentable carbohydrates, other available nutrients, presence of inhibitory compounds, O₂ level, pH, and fermentation temperatures. The temperature, salt concentration, and pH have major effects on the rate and extent of fermentation by LAB. It takes a shorter time when the temperature is increased and the salt concentration decreased.

Fermentation is carried out mainly by cabbage LAB after the brining process; other MOs present in ingredients other than cabbage may also be involved in the fermentation, but LAB from the brined cabbage seems to be the main natural starters [13]. It is important to maintain facultative anaerobic conditions to minimize the growth of aerobic MOs and to stimulate the growth of LAB during fermentation.

The LAB kinds and populations present during kimchi fermentation vary with pH and acidity. Kimchi fermentation can be devided into 4 stages based on acidity: initial stage (acidity < 0.2), immature stage (acidity 0.2–0.4), optimally ripened stage (acidity 0.4–0.9) and overripened stage (acidity > 0.9). The pH and acidity of optimally ripened kimchi are pH 4.2–4.5 (average 4.3) and 0.4–0.8% as lactic acid, respectively [3, 14].

Jung et al. [15] presented the phylogenetic classifications of the 16S rRNA gene sequences for kimchi LAB. In early fermentation, the proportion of unclassified phylotypic groups, including unclassified Deferribacterales and other unclassified bacteria was highest (J1-97%). Kimchi fermentation was controlled by 3 genera, Leuconostoc spp. (Leu), Lactobacillus spp. (Lab) and Weisella spp. (Wei). The genus Leu was most abundant during kimchi fermentation, following Lab and Wei. Leu dominated at the beginning stages. The abundance of Lab and Wei increased as the fermentation progressed. After the middle stage, Leu, Lab and Wei became the predominant bacterial groups in the microbial community, and the abundance reached ~ 80% after day 23. When the unclassified phylotypic groups were excluded from the analysis, the 3 predominant bacterial groups constituted more than 98% of all bacterial groups. Thus the representative genera involved in kimchi fermentation are 3 genera of Leu, Lab and Wei, and the major LAB compositions are depending on the fermentation time, temperature and other fermentation conditions; however, better starters are employed for constant quality, taste and specific functionalities [16].

LAB communities found in 9 commercial kimchi samples in markets from representative Korean kimchi companies were studied [8]. The total LAB counts ranged from 1.3 $\times$ 10⁷ to 1.6 $\times$ 10⁹ CFU/g (mean was 7.7 $\times$ 10⁸ CFU/g). pH values were from 4.3 to 4.7 (mean was 4.4). Weisella, Lactobacillus and Leuconostoc were the dominant genera accounting for 52%, 28%, and 20%, respectively, of the identified genera by a pyrosequecing method. Weisella. considered Leuconostoc subspecies before 1999 [17]. Thus, Leu and Lab were the main LAB found in kimchi previously. Wei. koreensis (34.4%) was dominant, followed by Lab. graminis (12.5%), Wei. cibaria (11.2%), L. sakei (9.2%), and Leu. gelidum (8.9%), Leu. mesenteroides (3.2%), Leu. kimchii, Leu. gasicomitatum, Leu. citreum, Leu. inhae, others were also identified in the kimchi samples. The bacterial strains isolated from commercial kimchi were specially heterofermentative LAB, which gives good taste. Leu. citreum [18], Leu. mesenteroides [19], mixed cultures of Leuconostoc mesenteroides (Leu. mesenteroides) and Lactiplantibacillus plantarum (L. plantarum) [20], which showed better probiotic effects and tastes, have been employed as starters for kimchi fermentation. Better starter cultures or combinations will be employed for the kimchi industry.

Health functionality of kimchi

In the past, kimchi was used as a protective food during the winter (when there were no vegetables or fruits in winter). Additionally, vegetables contain probiotic LAB that are naturally present, making it a fermented food made with LAB. It is a naturally low-calorie food and contains vitamins, minerals, dietary fiber, and other fermented functional substances. The functional phytochemicals include isothiocyanates, indole-3-carbinol, allyl sulfur compounds (allicin, diallyl sulfide, etc.), capsaicin, β-sitosterol, ascorbic acid, carotenoids, flavonoids, tocopherol, selenium (Se), dietary fibers, polyunsaturated fatty acids (PUFA), etc. and live LAB contribute to kimchi fermentation. There are many fermentation metabolic products from the ingredients that participate. Therefore kimchi is a health food that contains probiotics, prebiotics, and postbiotics. Fermented foods are said to increase the diversity of the microbiome, suppress inflammation, and prevent chronic diseases, making them much more beneficial to health than foods that produce SCFAs through a high-fiber diet [21]. Protein and fat can also be increased by adding fish, shellfish, and meat, and functionality can also be improved by adding other highly active vegetables or fruits. In addition, functional kimchi customized for disease prevention can be developed. Therefore, by adding various types of auxiliary ingredients and necessary ingredients, the functionality can be further improved while maintaining its taste.

The functionality of kimchi is 1. Antioxidant and antiaging effects; 2. Food sources of probiotics, prebiotics, and postbiotics; 3. Cancer-prevention effect; 4. Improving of colon health; 5. Control of lipid profiles and metabolic syndrome; 6. Control and reduction in body weight; 7. Others (promotion of immune function and appetite, etc.) [2,3,4,5]. This review mainly reports the antiobesity and anticancer effects of kimchi.

Antiobesity effect of kimchi

Antiobesity effects of kimchi in vivo and in human studies

The SD rats were fed diets containing RPP (red pepper powder) or kimchi powder with a high fat (HF) diet. When the rats were fed a 5% RPP with HF diet, the body weight (BW) significantly decreased to 311.0 ± 9.5 g compared to that of HFD only group (338.7 ± 13.4 g) after 4 weeks of feeding. However, 10% kimchi in the HF diet (containing the same level of 5% RPP as that of dried kimchi) decreased the BW to 302.6 ± 11.3 g (p < 0.05), which was the same as the BW of normal mice of 305.7 ± 12.7 g [22]. RPP contains capsaicin that gives hot taste of kimchi and stimulating spinal nerves and subsequently releasing the catecholamine in the adrenal glands. This can promotes metabolism and the expenditure of energy [23]. In the organ weights of the rats, kimchi significantly reduced the weights of liver, epididymal fat pad and perirenal fat pad, although the weights of the spleen and kidney did not different among the groups. The antiobesity effect of kimchi in rats is due to the combined effects of the kimchi ingredients of cabbage, radish, RPP, garlic, ginger [24, 25], fermented products, LAB, etc. [26,27,28,29,30].

Baechu kimchi which has RPP showed antiobesity; however, whitish kimchi (called Baek kimchi) without RPP also revealed strong antiobesity effect [31]. Yoon et al. [25] reported that major Korean spices (RPP, garlic and ginger) in kimchi exhibited antiobesity effects on SD rats fed a high fat diet. Garlic and ginger had better antiobesity effects than RPP. The garlic and ginger diet groups had markedly lower weights of liver, epididymal and perirenal fat pads, and also decreased TG, and total cholesterol (TC) levels in serum, liver and the fat pads compared to the other groups.

Kimchi has shown antiobesity effects in humans. Kimchi capsules (500 mg/capsule) were prepared with freeze dried kimchi powders (3 and 6 g/days) for the groups of obese women. They were exercised aqua aerobics for 1 h once a week [32]. Body weight and BMI significantly decreased after 8 weeks with 3 g or 6 g of kimchi capsules/day supplementation. The body weights decreased from 64.5–65.4 kg to 58.8–59.5 kg (Fig. 2A) and BMI also decreased from 25.6–25.9 to 23.3–23.7 for the first 8 weeks. TG levels decreased from 125.8–142.7 (pre) to 63.8–65.4 mg/dL (post). HDL increased from 28.9–29.4 (pre) to 44.6–47.4 mg/dL (post) (Fig. 2B). This study indicated that the visceral fat area and the levels of serum TG and HDL were modulated by the administration of kimchi capsules.

Fig. 2

Changes in the body weight (A), and triglyceride and HDL levels after 8 weeks (B) of obese women who consumed kimchi capsules as a supplement to exercise. DK, Diet kimchi; DK0, obese woman who had not taken kimchi capsules; DK3, obese woman who had taken 3 g of kimchi capsules; DK6, obese woman who had taken 6 g of kimchi capsules [32]. ^*p < 0.05

The consumption of kimchi reduced body weight, BMI and % body fat in over weights and obese subjects which might reduce the risk for CVD and metabolic syndrome [26]. The authors indicated that, compared with fresh kimchi fermented kimchi intake decreased the waist-to-hip ratio, fasting blood glucose, fast insulin, total cholesterol, MCP-1 and leptin levels. They concluded that the maturity of kimchi fermentation affects obesity, lipid metabolism and inflammatory processes. Aerobic exercise combined with kimchi supplementation had a greater effect than exercise alone or kimchi alone. Kimchi supplementation combined with exercise could decrease obesity and improve plasma lipid profiles in obese middle school girls [33].

Antiobesity kimchi with green tea leaves

To increase the antiobesity functionality of kimchi, Choi [34] developed kimchi by adding green tea leaves. Kimchi with green tea leaves (GTL) inhibited the growth of 3T3 F442A cells. In addition, regarding lipid metabolism in rats, it was reported that the group administered GTL kimchi had the lowest weight gain and dietary efficiency, and the lipid peroxide content was low. Lee et al. [35] confirmed the antiobesity effect of FK (functional kimchi) using 5% green tea leaves and bamboo salt and MSFK (mixed starter-fermented functional kimchi) with starters of Lactiplantibacillus plantarum (L. plantarum) and Leuconostoc mesenteroides (Leu. mesenteroides). FK and MSFK significantly reduced body weight compared to that in the HFD group (p < 0.05). A decrease in serum TG, TC, low-density lipoprotein cholesterol (LDL), and leptin and an increase in the amount of high-density lipoprotein cholesterol (HDL) and adiponectin were confirmed. The levels of the adipogenesis-related factors CCAAT/enhancer binding protein α (C/EBP-α) and peroxisome proliferator-activated receptor-γ (PPAR-γ) in the liver were also decreased. Hong et al. [36, 37] developed kimchi (catechin functional kimchi, CFK) by adding catechin, an active ingredient in green tea that has antiobesity effects, and lactic acid bacteria (LAB) as a starter. Four types of kimchi (CK, commercial kimchi; SK, standard kimchi; GFK, GTL functional kimchi; CFK, catechin functional kimchi) were orally administered to C57BL/6 mice along with a 45% high-fat diet for 16 weeks, and body weight changes in each group were evaluated. The CFK group weighed 41.17 ± 3.00 g, a significant decrease of 15.95% compared to that of the HFD group (48.98 ± 2.18 g) (p < 0.05), and showed the highest weight loss effect was observed among the groups that were administered the other three types of kimchi (CK, SK, or GFK) (Fig. 3). Moreover, CFK reduced adipocyte and crown-like structures in liver and epididymal adipose tissues [37]. Compared to those in the groups that administered kimchi (CK, SK, GFK, and CFK), the HFD group exhibited irregular cell arrangement and lipid accumulation around the central vein of liver tissue. On the other hand, the number and size of fat globules in liver tissue in the groups that were administered kimchi were significantly smaller than those in the HFD group (p < 0.05). In particular, it decreased by 36.67% in the group that was administered CFK, demonstrating the effect of suppressing fat accumulation in the liver. In the epididymal fat tissue, the HFD group accumulated lipids, increased the volume of adipocytes, and showed irregular cell arrangement compared to the groups that were administered kimchis. It was significantly reduced by 53.05% in the CFK group (1101.46 ± 211.76 μm²) compared to the HFD group (2346.04 ± 433.29 μm²) (p < 0.05). In addition, it was significantly lower (59.24%) than that in the Salt group (2702.08 ± 476.13 μm²), which is thought to suppress obesity more than NaCl is due to the various minerals contained in the solar sea salt used to make kimchi. In liver and epididymal fat tissues, the protein expression of adipo-/lipogenesis-related genes such as C/EBPα, PPARγ, sterol regulatory element-binding protein-1 (SREBP-1), lipoprotein lipase (LPL), diacylglycerol O-acyltransferase (DGAT)1, and DGAT2 was significantly lower in the CFK group than in the HFD group, and the protein expression of lipolysis-related genes such as hormone-sensitive lipase (HSL) and carnitine palmitoyl transferase 1 (CPT-1) was increased. Additionally, the protein expression of inflammation-related genes was decreased in epididymal fat tissues. The protein expression of TNF-α in the CFK group was significantly lower than that in the HFD group, and the TNF-α expression was 5.06 times lower in the CFK group than in the Salt group (p < 0.05). The protein expression of IL-6 in the CFK group was significantly lower (68.58%) than that in the HFD group. Obesity is also known to affect the intestinal microbial community [38]. Bacteroidetes in the HFD group was only 5.64%, and the abundance of Firmicutes, which is known to promote weight gain observed in obesity [39] was 87.15%, an increase of 18.03% in Firmicutes (69.12%) compared with those in the Nor group. NaCl reportedly affects intestinal microorganisms, as the Salt group presented a greater abundance of Firmicutes (84.51%), and a lower levels of Bacteroidetes (3.32%) than the HFD group. In contrast, Bacteroidetes (7.61%) increased and Firmicutes (82.21%) decreased in the CFK group. Everad et al. [40] reported that body weight, fat mass, liver steatosis, and inflammation were reduced, intestinal Bacteroidetes was increased and Firmicutes was decreased in mice model of obesity and type 2 diabetes. Thus, the CFK group was reported to have an antiobesity effect by regulating the intestinal microorganisms of mice, such as increasing Bacteroidetes and decreasing Firmicutes.

Fig. 3

Effects of catechin functional kimchi (CFK) on the obesity of high-fat diet (HFD)-fed obese mice for 16 weeks of feeding. Nor, AIN-93G diet; HFD, 45% high-fat diet; Salt, 45% high-fat diet and 1.5% NaCl; CK, 45% high-fat diet and 1.5 mg/kg/day commercial kimchi; SK, 45% high-fat diet and 1.5 mg/kg/day standard kimchi; GFK, 45% high-fat diet and 1.5 mg/kg/day green tea functional kimchi; CFK, 45% high-fat diet, and 1.5 mg/kg/day catechin functional kimchi. Mean values with different letters (a–f) at 16 weeks are significantly different (p < 0.05) according to Duncan’s multiple range test [36]

As a result of confirming the antiobesity effect of kimchi according to the type of salt, it was reported that the expression of lipolysis and β-oxidation genes such as HSL and CPT-1 increased significantly in WDSK kimchi (kimchi prepared with washed and dehydrated solar salt) samples compared to kimchi samples using in other salts, increasing lipolysis and β-oxidation [41, 42]. These results are due to differences in the mineral composition of solar sea salt, and it was announced that the level of Mg was a major factor in the taste and antiobesity effect of kimchi.

Antiobesity of kimchi LAB

Kimchi LAB powder (containing 9.1% kimchi LAB extract, KL) decreased the body weight and lipid-lowering activities in SD rats fed a high fat (HF) diet. The HFK10 (10%) and HFK20 (20%) KL supplement groups had 39–46% lower body weights than did the HF diet after 17 weeks. Plasma TG, cholesterol and LDL levels significantly lowered, and high levels of TG and cholesterol were excreted in the feces [29]. Similarly, compared with those in the control group, the amount of visceral fat in the HFK10 and HFK20 groups was markedly decreased by 42 and 48%, respectively.

Moon et al. [27] reported that Wei. koreensis OK 1–6 was isolated from kimchi, and showed an antiobesity effect on 3T3-L1 cells. Spent culture media extract and the cytoplasmic fraction of Wei. koreensis OK 1–6 reduced the expression levels of lipogenic genes, and decreased TG levels in 3T3-L1 cells compared to those in the control group. The mRNA expression levels of C/EBPα, which is involved in adipocyte differentiation were significantly decreased in 3T3-L1 cells by the treatment of the Wei koreensis OK 1–6. The expressions of the aP2, FAS, and SREBP1 genes were also significantly lowered (p < 0.05). When kimchi was fermented with Wei koreensis OK 1–6 as a starter, the antiobesity effect of the kimchi markedly increased in high fat diet induced obese mice [30]. The authors indicated that the taste of Wei koreensis OK 1–6 fermented kimchi was indistinguishable from that of the traditionally fermented kimchi according to sensory evaluation.

Lee et al. [28] studied kimchi LAB, L. plantarum strains (4 × 10¹¹cells/kg/d) on their antiobesity effects. Dead L. plantarum nF1 (nLp), live L. plantarum pF1 (pLp) and live L. plantarum PNU (PNU) were studied in C57BL/6 mice fed a 45% high fat diet for 8 weeks. The body weight, and weights of the liver and epididymal fat of mice fed nLp were significantly lower than those of mice in the pLp, PNU or control groups (p < 0.05). The levels of serum TG, total cholesterol, glucose, and insulin were significantly lower in the nLp, pLp, and PNU groups than in the control group; however, the nLp group had the lowest levels. Adiponectin and HDL-cholesterol level were markedly greater in the nLp group than in the pLp, PNU and control group. Histological observation of nLp revealed low fat accumulation in the liver tissue. Kimchi L. plantarum strains significantly reduced the mRNA level of SREBP-1C, while increased PPAR-α, CPT-1 and ACO in the liver, and also increased PPAR-α and CPT-1 in epididymal fat tissues. The nLp strain of postbiotic had greater antiobesity effects on the mice than did the live pLp and PNU strains in this study. As shown in Table 1, initial body weights of the mice were 22.3–22.9 g. The final body weights after 8 weeks were 29.6 ± 1.2 g of normal group, however, HFD fed mice was 41.4 ± 1.3 g, and nLp, pLp and PNU groups were 37.5 ± 2.3 g, 38.4 ± 1.2 g, and 40.0 ± 2.8 g, and reduction rates were 35%, 28%, and 16%, respectively compared to the HFD group. Thus, live or dead, LAB have antiobesity effect depending on the strains with better serum lipid profiles and modulate antiobesity related genes in mice.

Table 1 Effects of L. plantarum strains on the body weight, food intake and food efficiency ratio (FER) of high fat diet (HFD)-induced C576L/B mice

Preventive effect of kimchi on cancer

Antimutagenic, anticarcinogenic, and anticancer effects in vitro and in vivo

Kimchi showed antimutagenic activities against aflatoxin B₁ (AFB₁) in the Ames test, and SOS chromotest in vitro [43,44,45,46], The kimchi extract also exhibited antimutagenic activity in the Drosophila wing hair spot test in vivo [47]. C3H10T1/2 cells are mouse embryo cells that form foci in culture media when exposed to carcinogens. The foci, developed as type 2 and 3, are strongly correlated with tumor formation in C3H mice, 50% and 85%, respectively [48]. When MSF (methanol soluble fr, 200 µg/mL) from 3 week fermented kimchi at 5 °C was added along with 3-methylcholanthrene (MCA) to the cells, then the numbers of type 2 and 3 foci formed decreased significantly from 7.4 to 0.8 [49].

The cell body of kimchi LAB exhibited antimutagenic activities in Ames mutagenicity test and SOS chromotest. The mutagenicities mediated by 4-NQO (4-nitroquinoline-1-oxide), MeIQ (2-amino-3,4-dimethylimidaze [4,5-f] quinooxide), Trp-P2 (3-amino-1-methyl-5H-pyrido [3-b] indole) were suppressed by kimchi LAB in both tests [50]. The LAB, Leu. mesenteroides, Lab. brevis, Lab. fermentum, L. plantarum revealed high activity of prevention the mutation. Park et al. [51] reported that the mutagenicity was found in the cell wall fraction rather than in the cytosol fraction. Glycopeptides from peptidoglycan in the LAB cell wall showed antimutagenic [52]and antitumor effect [53]. Thus whether the LAB were viable or not, the activities were effective.

The anticancer kimchi that we developed for example to improve anticancer function by the addition of functional subingredients. Organically cultivated Baechu cabbage, Chinese pepper, Korean mistletoe extract, mustard leaf, solar sea salt or bamboo salt, starter cultures of L. plantarum and Leu. mesenteroides and postbiotic of L. plantarum nF1 could be used [12].

Kimchi showed an anticancer effect on in vitro human cancer cells. The kimchi extracts inhibited the survival or growth of human cancer cells (AGS, HT-29, MG-63, HL-60, and Hep3B) in the SRB, MTT and growth inhibition tests [11, 45, 54]. The kimchi fractions also inhibited ³H thymidine incorporation in the cancer cells [55].

In vivo studies, sarcoma 180 cells were transplanted to the Balb/c mouse followed by kimchi extracts were injected, and the MSF of the kimchi treated group resulted in the smallest tumor weight of 1.98 ± 1.8 g (54% inhibition) compared to that of the control group 4.32 ± 1.5 g [56]. MSF increased the hepatic cytosolic glutathione content and the activities of glutathione S-transferase and glutathione reductase, indicating that kimchi might also be involved in the detoxification of xenotoxic materials in the liver.

Kimchi extracts enhanced the immune function of NK cells and macrophages [12, 45]. The antimutagenic, anticancer, antimetastatic and NK cell activities of kimchi could be increased by manipulating the kinds and levels of the ingredients including salt kinds and the fermentation methods [11, 54, 57]. Lung metastasis with colon 26M3.1 cells significantly decreased by subcutaneous administration of kimchi extract in mice following the tumor cell inoculation with common kimchi and even greater with the functional kimchi we developed [4].

Gastritis and gastric cancer prevention

Helicobacter pylori infection is considered as a major risk factor for gastric cancer. SK (standardized kimchi) and CP (cancer preventive) kimchi [58, 59] were treated in AGS gastric cancer cells and RGM-1, nontransformed gastric epithelial cells. As shown in Fig. 4A, CP kimchi (CPK) was cytotoxic at > 5 mg/mL in AGS cells; however, in nontransformed gastric mucosal cells from RGM-1, no cytotoxicity was detected. CPK was more cytotoxic to AGS cells than SK, but not to normal cells, which indicated that CPK selectively induced cytotoxicity in cancer cells. The expression of HO-1 (heme oxygenase-1) was significantly increased in both RGM-1 and AGS cells treated with CPK; however, the expression of HO-1 was markedly greater in RGM-1 cells (Fig. 4B). The cytotoxic effects of CPK were blunted in noncancer cells through increased induction of the cytoprotective gene HO-1. It seems that the increased cytotoxicity in AGS cells, and lack of cytotoxicity in noncancer cells caused by kimchi might be related to the selective apoptotic action of kimchi on the cancer cells. The western blot expressions for Bax and cleaved caspase 3 increased with CPK kimchi in AGS cells [59].

Fig. 4

Biological actions of standard kimchi (sKimchi) and cpKimchi; comparison in an in vitro H. pylori cell model. A Cell survival assessed by MTT assay. MTT assay were performed on AGS cells (up) and RGM-1 cells (down) challenged with 1, 2.5, 5, or 7.5 mg/ml sKimchi and cpKimchi soluble extracts. Kimchi at concentrations greater than 5 mg/ml had significant cytotoxic effects only on AGS cells and not on RGM-1 cells even after kimchi treatment at concentrations greater than 5 mg/ml. B Western blot of HO-1 after each kimchi extract [59]

Kimchi samples were administered to chronic H. pylori-initiated and high salt diet-promoted gastric tumorigenesis mice model. Erythematous and nodular changes, mucosal ulcrative and erosive lesions in the stomach were observed at 24 weeks, but CPK administration significantly ameliorated these changes. Scattered nodular masses, some ulcers, and thin nodular gastric mucosa were noted after 36 weeks in H. pylori infected mice; however, these gross lesions were decreased in the CPK group. Protein expressions of COX-2, IL-6, activated NF-κB, STAT 3, etc. were observed in the H. pylori-infected group related to tumorigenesis, but these factors were significantly reduced in the CPK group.

Long term intake of CPK prevented H. pylori induced gastric tumorigenesis in C57BL/6 mice [59]. H. pylori initiated high salt diet feeding promoted, gastric tumors and a severe degree of chronic atrophic gastritis at 36wk. Pathology revealed that these gross lesions were severe chronic atrophic gastritis, gastric ulcers, gastritis, adenoma and adenocarcinoma. The whole gross lesion index was significantly greater than in the control group, but was significantly lower in the group administered CPK. Similar results were observed for gross appearance according to the pathological score analysis. The control group exhibited significant tumorigenesis according to the gross observation, adenoma or adenocarcinoma, but gastric tumorigenesis was markedly reduced with CPK administration. Thus CPK, which is a cancer preventive ingredients for kimchi significantly prevented for gastric cancer in mice.

Kil et al. [60, 61] reported that 300 g of kimchi/day was administrated to H. pylori infected subjects during the kimchi phase, followed by 4 week of control phase (60 g of kimchi/day). Similarly, delta over baseline (DOB) level during the kimchi phase was lower than that during the control phase (p = 0.9439). Kimchi intake did not significantly reduce H. pylori levels in a short period of time in a clinical trial; however, functional kimchi and Lactobacillus sp. can inhibit the growth of H. pylori. Lee and Chang [62] isolated L. plantarum NO1 and the culture medium of L. plantarum NO1 reduced (40–60%) the urease activity of H. pylori KCCM 41756, resulting in anti-H. pylori activity.

Colon cancer prevention and colon health benefits

Colorectal cancer (CRC) is associated with IBDs (inflammatory bowel diseases), which include ulcerative colitis (UC). Chronic inflammation is important for the pathological process of CRC. High levels of proinflammatory cytokines, overexpression of iNOS and COX-2, and other factors are also involved in colorectal carcinogenesis in mice [63, 64]. Kim et al. [58] reported that kimchi can prevent AOM/DSS induced colorectal carcinogenesis in mice. After exposure to AOM/DSS, 1.89 g/kg of ACK (anticancer kimchi) increased the colon length, decreased the ratio of colon weight/length, and lowest number of tumors. Kimchi suppressed colony-like mucosal damage and neoplasia. AOM/DSS caused histological alterations in the colonic mucosa, including infiltration of inflammatory cells into the lamina propria, loss of crypts and adenocarcinoma development. Low grade dysplasia was observed in the colon tissue of the ACK-treated mice, and colonic epithelium was restored.

ACK can decrease the mRNA levels of proinflammatory cytokines (IL-6, TNF-α, and IFN-γ), and the mRNA and protein expression on p53 and p21 increase in colon tissues. Kim et al. [58] shows the control significantly increased the mRNA and protein expression of iNOS and COX-2 in the colorectal tissues of the mice; however, the kimchi treatment decreased the mRNA and protein levels. Similarly, compared with the control, expression of these genes was reduced by almost 50–80%. Kimchi suppressed AOM/DSS induced colorectal carcinogenesis in Balb/c mice. In particular, the addition of health-promoting subingredients to ACK significantly exacerbates its ability to prevent colon carcinogenesis [58].

Kimchi also showed a beneficial effect on colon health by increasing probiotic LAB from kimchi and decreasing toxic enzyme activities and pH in the colon [60]. The counts of Lactobacillus sp and Leuconostoc sp in the feces significantly increased during the kimchi phase (300 g kimchi/day for 4 weeks). β-Glucosidase and β-glucuronidase, which can convert procarcinogens to carcinogens in the colon, were significantly decreased, and the pH was also decreased during the kimchi phase. Kim et al. [65] studied the effect of kimchi consumption on IBS patients in clinical trials. Kimchi intake effectively reduced IBS symptoms and inflammation. Three kinds of kimchi samples (SK, nLp SK and FK) (210 g kimchi/day) were supplied for 12 weeks. Dietary fiber intake increased after the intervention. The IBS symptoms (abdominal pain or inconvenience, desperation, incomplete evacuation and bloating), defecation time and stool type were all significantly improved. The serum levels of the cytokines of IL-4, 10, and 12 were significantly lowered in the nLP SK (L. plantarum nF1, postbiotic added to SK, standardized kimchi) and FK (functional kimchi). In addition, MCP-1 (monocyte chemoattractant protein-1) was decreased in the nF1 SK group. Fecal β-glucosidase and β-glucuronidase were significantly decreased in the IBS patients who consumed the three kinds of kimchi samples.

The kinds of salt affect the taste and functionalities of kimchi

Most fermented foods in Korea, especially kimchi and soybean fermented foods, use salt(generally solar sea salt) for fermentation by microorganisms, including LAB, for long periods of preservation. When salting cabbage in kimchi preparation the levels of spoilage and pathogenic microorganisms are markedly reduced; however, LAB that can survive in salted conditions can multiply and become the main starters for kimchi fermentation. The salt content of traditional kimchi products was 1.5–5.0%, depending on the regional temperature, preference for kimchi preparation. We have studied various levels and kinds of salt to improve the taste and functionality of kimchi. Typical kimchi that contained 3% salt had an antimutagenic effect on MNNG (N-methyl-N´-nitro-N-nitroguanidine), but a much greater percentage of kimchi salt (9.5–10.5%) exhibited a comutagenic effect on MNNG [43].

The quality and anticancer effect of kimchi are affected by changing various kinds of salt [66]. Purified (> 99% NaCl), solar sea salt (nautral sea salt), natural sea salt without bittern (NS-B), and guwun salt (baked salt) were used for the preparation of kimchi. The tastes and anticancer effects of NS-B and baked guwun salt were better than those of purified salt, which does not have sea minerals.

Cui [67] prepared SK (standardized kimchi with general solar sea salt), ACK (anticancer kimchi with general solar sea salt), ACBK (anticancer kimchi with three times baked (3×) bamboo salt), and ACBSK (anticancer kimchi with 3× bamboo salt with starter of L. plantarum). The bamboo salt used in kimchi increased the LAB counts, springiness of the kimchi, and exhibited greater antioxidative and anticancer effects on human colon cancer cells than SK and ACK.

As shown in Fig. 5A, the overall acceptability of ACBK was markedly greater than that of ACK according to the sensory evaluation of the kimchis. The ACBK and ACBSK groups also exhibited significantly increased anticancer effects on the growth of HT-29 human colon cancer cells in MTT assay (Fig. 5B). Cytokines and apoptosis related genes were modulated by changing salt, bamboo salt in kimchi (ACBK) from general solar sea salt (SK, ACK) during kimchi preparation for AOM/DSS induced colon cancer in vivo.

Fig. 5

Sensory evaluation of bamboo salt (3 times baked) added kimchi (optimally ripened) after 3 weeks fermentation at 4 °C (A). And inhibitory effect of the kimchi extracts on the growth of HT-29 human colon carcinoma cells (B). Means with different letters on the bars are significantly different (p < 0.05) according to Duncan’s multiple range test. SK: standardized kimchi, ACK: anticancer kimchi, ACBK: anticancer kimchi prepared with bamboo salt, ACBSK: ACBK + starter of L. plantarum

The washed and dehydrated solar sea salt or solar sea salt that removed bitterns for 3 years naturally exhibited a better taste in kimchi and the best anticancer and antiobesity effects [42]. The salt that contains sea minerals and appropriate Mg content were very important factors for the kimchi tastes and functionalities. When the concentration of Mg, K, and S contents removed about 30–60% from the general solar sea salt, the taste, anticancer, and antiobesity activities of the kimchi increased. They employed an experiment on a combined animal model of colorectal cancer and obesity, and the results were significantly affected by the kinds of salt used. WDSK-S (washed-dehydrated solar salt brined kimchi with a starter of L. plantarum) had the best taste, and anticancer and antiobesity effects on the kimchi, followed by WDSK (washed dehydrated solar salt brined kimchi) and CSK (conventionally manufactured solar salt brined kimchi), and PSK(purified salt brined kimchi). PSK exhibited the lowest overall acceptability of the kimchi panel for taste, anticancer and antiobesity activities. Other data on liver wt, spleen wt, epididymal fat wt and histopathological changes in the mice also showed the same trends in the order of WDSK-S, WDSK, CSK and PSK. The anti-inflammatory effect was the highest in WDSK-S and the activity was the highest in the order of WDSK-S, WDSK, CSK and PSK. Thus the type of salt is an important factor, and these results indicated that LAB fermentation is strongly influenced by the type of salt, specially the optimal mineral levels of the salt for fermentation.

The mineral content of solar sea salt can be affected by the marine environment, processing methods of the sea salt. The ICP-OES data demonstrates that the Mg and S contents in WDS (washed-dehydrated solar salt) were 3 times lower than CS (conventional manufactured solar salt) and FS (filtered sea water solar salt). Mg and K cause a bitter taste [68]. Kimchi prepared with WDS which reduces Mg levels exhibits a significantly better taste and greater anticancer effect [69]. Mineral composition analysis revealed that the Mg and S contents in the 4 types of solar sea salt were different depending on the processing method. Mg and S contents in WDS were reduced by 47.5% and 30.9%, respectively, compared with those in CS. In our studies, when Mg was maintained at an optimal level, which was indicated by a bell shape curve, it exhibits greater anticancer and antiobesity effects. This means that an appropriate level of Mg in the salt for kimchi preparation, especially for kimchi taste and functionality, can be improved [69]. We recommend that Mg contents range from 7.6–9.3 kg⁻¹ and that S contents range from 4.2–4.7 kg⁻¹ [69]. WDSK (washed-dehydrated solar salt brined kimchi) had the best taste and the best anticancer effect on HT-29 human colon carcinoma cells, as shown by p21 and p53 expression. WDSK had the greatest taste and anticancer effect, followed by DSK (dehydrated solar salt kimchi) FSK (filtered solar salt kimchi), and CSK (conventional manufactured solar salt kimchi).

Postbiotics in kimchi

Kimchi, especially from Kimjang culture in Korea, is aged from early winter to the following spring, and Koreans like aged kimchi to make side dishes and various cuisines. They can use heated kimchi side dishes, such as kimchi jigae (kimchi stew), or kimchi jeon (pancake).

Postbiotics and their functions

The number of dead LAB cells markedly increased in a manner dependent upon ripening or an increased fermentation period. Recently, postbiotics were defined as intact inanimate dead microbial cells and/or microbial cell fragments/structures, with or without metabolites and end products, that confer a health benefit on the host [70]. The components include intact inanimate microbial cells such as microbial cell fragments/structures of cell walls, membranes, exopolysaccharides (EPS), cell wall anchored proteins, pili, etc., and with or without metabolites or fermented products of organic acids, short chain fatty acids (SCFA), bacteriocins, proteins, enzymes, etc.

Cell wall materials in the microorganisms are important in postbiotics for the health functions [71]. There are pili, cell wall associated proteins, secreted proteins, S-layer proteins, EPS, peptidoglycan, wall teichoic acid (WTA), lipoteichoic acid (LTA), etc. in the inanimate or dead microbial cells.

Many recent studies have been carried out on the use of probiotics, prebiotics, postbiotics, human microbiome dysbiosis agents and fermented foods for the benefit of the health of the host and microbiota. Postbiotics have been used with different terms in the literature. They used heat killed probiotics, nonviable probiotics, paraprobiotics, tyndallized probiotics and postbiotics; however, postbiotics have emerged as the most common term [70].

Teame et al. [71] divided the cell structural components and metabolites of probiotics into paraprobiotics and postbiotics, respectively. The paraprobiotics used were peptidoglycans, surface proteins, cell wall polysaccharides, teichoic acid, lipoteichoic acid, EPS, S-layer proteins, pili proteins and moonlight protein. Secreated proteins and peptides, protein p40 and p75, aggregation-promoting factors, bacteriocins, SCFA, conjugated linoleic acid (CLA), neurotransmitters, etc. are used as the postbiotics. They can have positive effects on the host with immunomodulatory effect, antitumor, barrier preservation and antimicrobial activities.

SCFAs are an important metabolites that produced by the gut microbiota from fibers, oligosaccharides, and polysaccharides, and have positive effects on the host [72]. SCFAs are (1) regulators of gut metabolism, proliferation and differentiation; SCFAs especially butyrate are an energy source for intestinal epithelial cells (IECs) that are oxidized by β-oxidation in the mitochondria. The gut microbiota communicates with host cells via SCFAs and modulates a variety of cell mechanisms, Butyrate favors cell differentiation and inhibits proliferations. SCFA initiate apoptosis in cancer cells, and activation of Bax, caspase 3, p21, and p27 in cancer cell growth [73]. (2) SCFAs regulate gut endocrine functions; SCFAs increase the differentiation of epithelial cells into L-cells with higher GLP-1, PYY and serotonin production [74,75,76,77]. (3) SCFAs such as butyrate reduces epithelial permeability by regulating of occludin, zonulin and claudins [78] and increases Muc-2 production both in vitro and in human colonic biopsies in the barrier function [79, 80]. SCFAs also have anti-inflammatory effects by upregulating anti-inflammatory cytokines and downregulating proinflammatory cytokines [81].

EPSs (exopolysaccharides) are also important components of postbiotics. EPSs are glycan structures on the bacterial cell wall, It acts as polymers that directly influence bacterial interactions with their host. EPSs play a role in bacterial adhesion to the host epithelium of the gastrointestinal tract (GIT) through influencing on immune responses and the intestinal microbiota. The functions of the EPSs [82] are as follows. (1) Fermentation of EPSs by the intestinal microbiota results in the formation of SCFAs; EPSs can be used as prebiotic food supplements and are selectively utilized by host microorganisms [83] and produce SCFAs. (2) The effect of EPSs on bacterial adhesion to the intestinal epithelium; EPSs which is in surrounding the bacterial cell wall can shield surface proteins for adhesion. EPSs can reduce the adherence of pathogens to intestinal cells by shielding surface macromolecules from binding to adhesins [84]. (3) EPSs can maintain epithelial barrier integrity. The integrity of the host epithelial cell layer can be influenced by EPSs of various bacteria. Epithelial cells are sealed together by tight junctions. And (4) EPSs influence different cell types of both the innate and adaptive immune systems. EPSs can interact with different pattern-recognition receptors (PRRs) on immune cells, like TLR (Toll-like receptors), Dentin-1, etc. EPSs can also influence immune responses, B cells produce IgA, and naïve T cells become Th1, Th2 and Treg cells, which produce cytokines for further immune responses.

Mechanisms of postbiotics were postulated. (1) modulation of the resident microbiota, producing organic acids such as lactic acid, SCFAs, bacteriocins, adhesins, etc. (2) Enhancement of epithelial barrier function by SCFAs, EPSs, etc. (3) Modulation of systemic and local immune responses. (4) Modulation of systemic metabolic responses by bile salt hydrolase (BSH), succinate, vitamins, etc., and (5) systemic signaling via the nervous system by producing serotonin, dopamine, γ-aminobutylic acid (GABA), etc. [70]. The underlying mechanisms can be similar to those known for probiotics acting independently or in combination as postbiotics have heterogeneous mixtures of components. Bioactive compounds can be synthesized by resident microbiota and host epithelial cells though they are inanimate.

Dead Lab. paracasei D3-5 fed older mice maintained better physical and cognitive functions with reduced leaky gut and inflammation, showing antiaging effects [85]. Cell wall-derived LTA (lipoteichoic acid) was the key component responsible for enhancing Muc2 mRNA expression and mucin production from goblet cells. LTA activates TLR2 signaling and initiated downstream signaling cascade through the phosphorylation of p38-MARK [86]. LTA increased phospho-p38-MARK signaling, and Muc2 expression and goblet cell mass. LTA also downregulates NF-кB mediated proinflammatory responses in the intestine. Thus, LTA from the cell-wall in the postbiotics may prevent age-related gut microbiome dysbiosis, leaky gut, and inflammation.

Kimchi postbiotics and fermented foods

L. plantarum nF1 was isolated from kimchi, then it was pretreated with heat and nanodispersion process as postbiotics. nLp (nanometric L. plantarum) showed immunostimulatory activities, and increased IL-12 and IFN-γ production [87]. Heat treated dead L. plantarum (nLp) in our studies showed various functionalities. nLp increased immune functions. Choi et al. [87] reported that immunosuppressed by cyclophosphamide (CP) Balb/c mice significantly enhanced production of splenic cytokines of IL-12, TNF and IFN-γ. In addition, nLp also elevated NK cell activities and the serum levels of TNF, IL-2, and IL-12 in CP induced immunosuppressed mice [88]. nLp enhanced immune system when combined with several general foods, especially, when nLp added to yogurt and kimchi, the immune functions (cytokines, NK cell activity, etc.) greatly increased [65, 89, 90].

Lee et al. [91] studied on nLp and the addition of nLp to kimchi on DSS (dextran sulfate sodium)-induced mouse model of colitis. The nLp and nLp-kimchi fed animals presented lower levels of proinflammatory cytokines and inflammatory genes in the serum and colon tissues; lower levels of total bacteria; but higher counts of LAB in the feces; and lower activities of fecal β-glucosidase and β-glucuronidase. Thus, kimchi with nLp decreased DSS-induced colitis. Dead nanosized L. plantarum (nLp) inhibited AOM/DSS induced colon cancer in Balb/c mice [92]. The postbiotics, nLp had greater anticolorectal cancer activity than did of live, pure or intact L. plantarum (pLp). Furthermore, nLp strongly suppressed expression of the induction of inflammation, and increased cell cycle arrest and apoptosis markers in colon tissues, and enhanced IgA secretion.

Our recent study shows that the consumption of nLp in infants for 8 weeks with 5.0 × 10¹⁰/day significantly increased SCFAs production almost 5–8 times compared to that in the control group. We also observed that the microbial community markedly changed in the infant. Veillonella and Bifidobacterium levels significantly increased (p < 0.005); however, Bacteroides, Prevotella and Streptococcus abundances significantly decreased (p < 0.001) in the feces.

Fermented foods may be powerful modulators of the human microbiome-immune system axis and provide means to combat noncommunicable chronic diseases (NCCDs) [21]. They compared high fermented food diets (HFFD) and high fiber diets (HFD) in clinical studies. Fiber intake shifts the carbohydrate (CHO) processing capacity and metabolic output of the microbiota. The HFD increased 11-different CHO-active enzymes, and increased soluble fiber was less effective in improving inflammatory markers with decreased microbiome richness. However, in the HFFD, host inflammation markers decreased. In particular, the inflammatory cytokines of IL-6, and IL-12β decreased. HFFD increased microbiota diversity and decreased inflammatory markers and signals. The participants consumed a variety of fermented foods, such as yogurt, kefir, cottage cheese, kombucha, vegetable brine drinks, fermented vegetables, kimchi, etc. Thus, the diet, especially kimchi which contains good phytochemical vegetables, probiotics, prebiotics and postbiotics with fermented metabolites can modulate the gut microbiome and can impact the immune system and serve as a preventative food for NCCDs.

Healthy functional kimchi recipes could be developed. We have prepared kimchi with healthy food ingredients and fermented it with starters of L. plantarum and Leu. mesenteroides and better salt (washed-dehydrated solar salt or bamboo salt), and organic ingredients, especially organically cultivated baechu cabbage with postbiotics (Dead-nanosized L. plantarum nF1). Kimchi has increased antiobesity and anticancer activities and even better anti-inflammation and immune functions.

Conclusion

The main raw materials of kimchi are vegetables and condiments. The main ingredients are Brassica cabbage and radish, and the rest are seasonings such as red pepper powder, garlic, and ginger, which are good for taste and health. During natural fermentation, probiotic lactic acid bacteria (LAB) are present, and when fermented, LAB levels increases to 10^8–9 CFU/g, becoming probiotic foods. The dietary fiber present in the ingredients becomes a prebiotic source, food for the LAB, and a source of dietary fibers for humans. As kimchi is fermented, the number of dead bacteria that have passed the death phase increases during the growth and fermentation process, and when kimchi is heated during cooking, many of the LAB become dead cells, postbiotics.

Postbiotics are particularly involved in not only intestinal health but also the population of beneficial bacteria in the intestines, making the intestinal bacterial community beneficial to health. As kimchi is ripened, fermented metabolites produced from various phytochemicals, and other metabolites such as SCFAs can be produced in the gut from the intake of kimchi, resulting in health benefits. These combined compounds play major roles in suppressing inflammation and enhancing immunity. The type and amount of ingredients used are important, and if organic vegetables and good salts such as bamboo salt or washed and dehydrated solar sea salt are used for fermentation at least, kimchi with high antiobesity and anticancer activities can be produced. When fermentation conditions such as starters, temperature, oxygen levels, etc. are well controlled, the functionality even more increases. In addition, kimchi can be prepared with customized ingredients for specific disease prevention or health promotion purposes.