[www.mdpi.com]

There are two main methods through which foods are fermented. Firstly, foods can be fermented naturally, often referred to as “wild ferments” or “spontaneous ferments”, whereby the microorganisms are present naturally in the raw food or processing environment, for example sauerkraut, kimchi, and certain fermented soy products.

Secondly, foods can be fermented via the addition of starter cultures, known as “culture-dependent ferments”, for example kefir, kombucha and natto [2]. One method of performing a culture-dependent ferment is “backslopping”, in which a small amount of a previously fermented batch is added to the raw food, for example sourdough bread [1]. Starters used to initiate fermentation can be either natural (e.g., backslopping), or selected commercial starters to standardize the organoleptic characteristics of the final product [3].

Kombucha has been shown to exert effects in animal studies on blood glycaemia [72], oxidative stress [73], diabetes-induced weight loss [74], chemically-induced nephrotoxicity [75], hypercholesterolaemia [72,76] and indomethacin-induced gastric ulceration [77]. Compounds hypothesised to play a role in these beneficial effects include d-saccharic acid-1,4-lactone (DSL). This is produced by Gluconobacter during fermentation [78,79], and in rats, inhibits oxidative stress and diabetes-induced renal damage [80] and acetaminophen-induced hepatic injury [81].

Sauerkraut is one of the few fermented foods for which there is a clinical trial in functional bowel disorders. A randomised double-blind trial compared the effects of sauerkraut containing viable lactic acid bacteria (LA on gastrointestinal symptoms and microbiota in 58 patients with irritable bowel syndrome (IBS) of any subtype diagnosed using Rome III criteria [18]. Patients were randomised to consume 75 g/day pasteurised (control) or unpasteurised (intervention) sauerkraut containing LAB for 6 weeks. There was a significant reduction in IBS Severity Scoring System (IBS-SSS) score between baseline and end of trial in both study groups

Fermented soy products have been proposed to have beneficial effects on health, including purported “anti-carcinogenic”, “anti-diabetic”, “antioxidant”, “anti-inflammatory” and “anti-hyperlipidaemic” effects, although much of the existing evidence is limited to in vitro and animal studies [107].

Tempeh has been associated in vitro with greater free-radical and superoxide scavenging ability than unfermented soybeans [115], which may relate to changes in polyphenol content and digestibility in soybeans following fermentation [116,117].

The fermentation of Natto produces a number of bioactive factors, including nattokinase, bacillopeptidase F, vitamin K2 and dipicolinic acid [108].

A peptide with antibacterial activities against Streptococcus pneumoniae and Bacillus subtilis has been isolated from Natto [121], with potential clinical importance in treating S. pneumoniae infections

Nattokinase has direct in vitro [123] and in vivo [124] fibrinolytic activity, in addition to increasing tissue plasminogen activator [125] and reducing platelet aggregation [126]. Anti-thrombotic and anti-hypertensive activities of nattokinase have been demonstrated in small RCTs in humans [127,128].

A range of miso samples have also been shown to contain Lactococcus sp. GM005, which produces a bacteriocin with strong antibacterial activity that inhibits the growth of a range of bacteria, including Bacillus subtilis, Pediococcus acidilactici and Lactobacillus plantarum [130,131].

The high soy intakes in China and Japan have historically been hypothesised to contribute to the relatively low rates colon and prostate cancers in these countries [133]. One proposed mechanism to support this hypothesis is the high concentrations of isoflavones genistein and daidzein found in soybeans [134].

To produce kimchi, the cabbage is brined and drained, then the rest of the seasonings, spices and food products are added and mixed with the cabbage, and finally, fermentation takes place (134). The fermentation occurs spontaneously by the microorganisms naturally found on the cabbage and foods included in the mixture, although starter cultures may be used for commercial production of kimchi [20].

An animal study showed that kimchi consumption, which contained Leuconostoc mesenteroides DRC 0211, may exhibit potential weight control properties in mice via reducing hepatic mRNA expression of adipogenesis-related genes and inflammation-related monocyte chemotactic protein-1 and interleukin-6 in epididymal fat tissue [148].

A human study demonstrated that consumption of kimchi fermented for 8 weeks led to changes in expression of genes related to metabolic pathways and immunity [150]. In a mouse colitis model, Lactobacillus paracasei LS2, a strain isolated from kimchi, decreased cytokine production, myeloperoxidase activity, and the number of macrophages and neutrophils in the lamina propria lymphocytes, suggesting a potential anti-inflammatory effect [151].

It is worth noting the difficulty in undertaking and replicating fermented food studies given the significant variability of cultures and ingredients present even within food categories, which may partly explain heterogeneous findings.

The high soy intakes in China and Japan have historically been hypothesised to contribute to the relatively low rates colon and prostate cancers in these countries [133].

Apparently the soy intake of Chinese and Japanese populations is not all that high. I have read this many times over the years from several different sources. It is true that traditional Japanese have miso soup every day, but the soy content, while healthful (for reasons other than isoflavone content) is low. You know - like a teaspoon per bowl of soup.

FWIW and jes' passing it along.

Thanks. I took a quick look but don't know much

[thesoynutritioninstitute.com]

Quote
One analysis from the Shanghai Women’s Health Study (n=45,694) reported that daily mean intake of soy protein was 8.8 ± 6.3 grams.1 But the range of soy intake was wide. Slightly more than 2 percent of the women consumed at least 25 grams of soy protein per day while around 9 percent consumed less than 2.5 grams per day. The Shanghai Men’s Health Study (N=54,219) reported that daily mean intake of soy protein was 12.5 ± 7.94 grams.2 However, soy consumption varies considerably throughout China, and in some regions is one-third to one-half lower than in Shanghai.

Soy intake in Japan is more consistent throughout the country and is similar to what is found in Shanghai. Men enrolled in the Takayama Study (N=13,888) consumed 11.3 ± 7.8 grams of soy protein per day and women (N=16,424) consumed slightly less at 10.5 ± 7.0 grams.3 A much smaller study by the same author reported an intake of only about 8 grams of soy protein per day for men and 7 grams for women. But in both Japan and Shanghai, individuals in the fourth quartile or fifth quintile intakes consumed 15 grams or more of soy protein daily. The type of soy consumed varies among countries as well. In China, Singapore and Hong Kong, unfermented soyfoods, particularly tofu and soymilk, are the most commonly consumed products. 4 In Japan, about half of soy intake comes from the fermented foods natto and miso and the rest is tofu. 5,6

Finally, soy protein intake can be used to estimate isoflavone intake. In traditional soyfoods like tofu, soymilk and tempeh, each gram of protein is associated with approximately 3.5 mg of isoflavones. More refined products (such as isolated soy protein) are typically much lower in isoflavones, however, which are lost during processing. While soyfoods consumption varies greatly throughout Asia, the research answers important questions about intake. It is clear that soyfoods play an important role in the diets of many Asians and that both fermented and non-fermented foods contribute to intake.