Fermented Foods - How do they Actually Work?
Fermented Foods - How do they Actually Work?
The production of fermented foods and beverages was originally performed to enhance the shelf-life of perishable raw materials of agricultural and animal husbandry origin. Today, this bioprocess technology aims at the use of microorganisms and their enzymes, through acidification, alcoholisation, proteolysis, and/or amino acid conversions, to make products with desirable quality characteristics regarding shelf-life, texture, taste, mouthfeel, flavour, and colour. Moreover, it plays an important role not only in producing nutritious foods in a natural, rather cheap, and sustainable way worldwide but also in manufacturing foods with health-promoting properties.
Lactic acid bacteria (LAB; Firmicutes), yeasts (Fungi), and moulds (Fungi) are predominant in fermented dairy, meat, cereal, vegetable, alcoholic, and other fermented foods and beverages. Also, coryneforms (Actinobacteria) and acetic acid bacteria (AAB; a-Proteobacteria) play a pivotal role in the production of some of these products.
However, AAB are not studied to the same extent as many other food-grade and industrially important microorganisms. AAB are predominantly known for their use in the production of vinegar, vitamin C, and cellulose. Moreover, AAB are regarded as undesirable spoilers in alcoholic fermentations (wine, cider, and beer).
Cultivation and identification of acetic acid bacteria
One of the reasons why AAB have not been studied widely is that their cultivation, isolation, and identification is cumbersome, in particular during spontaneous food fermentation processes harbouring a wide variety of microorganisms and where they often occur as viable but not culturable (VBNC) cells. Challenging plating of AAB could be accommodated by optimising a selective agar medium, in particular modified deoxycholate–mannitol–sorbitol agar . Also, discriminatory high-throughput dereplication and identification techniques and high-throughput sequencing facilitate the determination of the abundance and functionalities of AAB in fermented foods and beverages.
Ecophysiology of Acetic acid Bacteria
AAB are commonly found on plants, flowers, and fruits. These aerobic environments are rich in carbohydrates, sugar alcohols, and/or ethanol. This enables AAB to rapidly and incompletely oxidize these substrates into organic acids for energy production through a specific respiratory chain. Consequently, an acidification of the environment takes place, thereby preventing the growth of competitors, while the producing cells possess several mechanisms to tolerate the acidity. Also, they can utilize the accumulated organic acids later to further sustain their growth. AAB cells capable of cellulose production form biofilms that allow their retention on the culture surface, which is favourable for the survival of these strictly aerobic bacteria. All these physiological features explain their occurrence and underlines their functional role in the production of diverse fermented foods and beverages such as lambic beer, water kefir, kombucha, and cocoa. Alternatively, AAB are associated with different plant and insect species, thereby promoting the growth and development of these species.
Kombucha
Kombucha is prepared with water, sugar, tea, and a kombucha culture (‘tea fungus’) in open vessels at room temperature for 1–3 weeks. This non-alcoholic beverage possesses a sharp acidity and specific flavour. The kombucha cellulose layer that composes the tea fungus and maintains the cells in close contact with oxygen is a consortium of bacteria (AAB and LAB) and yeasts responsible for the fermentation process, as revealed by metagenetic analysis.
The Health Benefits of Kombucha
Recently, several research studies have focused on enhancing the beneficial health potential of fermented herbal infusions. For example, a recent study reported that fermentation process with kombucha enhanced the phenolic content, antioxidant activity and α-amylase inhibitory activity in five commonly consumed teas. Similar results were observed by other scientists in fermented lemon balm (Melissa officinalis L.) infusion; they reported an enhancement of phenolic compounds such as rosmarinic, caffeic and ferulic acids (1.3-, 1.9- and 4.6-fold higher, respectively), as well as major antioxidant activity against DPPH radicals than in unfermented infusions.
The beneficial effects of these fermented beverages are attributed to the presence of restructured polyphenols, gluconic acid, glucuronic acid, lactic acid, vitamins, amino acids, antibiotics and a variety of micronutrients produced during fermentation.
The Fermentation Process
The fermentation process involves the activity of yeasts that ferment glucose and fructose to ethanol, which is then oxidized to acetic acid by acetic acid bacteria (AAB). The main source of carbon in this process is sucrose. The sugar is hydrolyzed by the enzyme invertase from the yeast present in the kombucha consortium, producing ethanol via the metabolic pathway of glycolysis, with a preference for fructose as the substrate. Subsequently, AAB convert glucose and ethanol into gluconic and acetic acids.
Which Bugs make Kombucha?
The most prevalent core microbiota in kombucha fermentation are AAB (high counts), which include Komagataeibacter and Gluconobacter species; Acetobacter species are less abundant. Komagataeibacter xylinus is responsible for the cellulose formation. Other AAB species have potential in both producing cellulose and fixating nitrogen. Although the microbial community composition of kombucha depends on the growth conditions of its members, such as available energy sources, temperature and oxygen tension, AAB are part of the relatively stable bacterial community and are responsible for the production of acetic acid (from ethanol), gluconic acid (from glucose), glucuronic acid (from glucose; detoxifying properties), and D-saccharic acid-1,4-lactone (from glucose; radical-scavenging; some Gluconacetobacter species). Hence, optimisation of production yields of glucuronic acid and antioxidative activities of kombucha is of importance.
Kombucha Kills Bugs – The Isorhamnetin Factor
The emergence of multi-drug-resistant enteric pathogens has prompted the scientist community to explore the therapeutic potentials of traditional foods and beverages. A recent study was undertaken to investigate the efficacy of Kombucha, a fermented beverage of sugared black tea, against enterotoxigenic Escherichia coli, Vibrio cholerae, Shigella flexneri and Salmonella Typhimurium followed by the identification of the antibacterial components present in Kombucha.
Kombucha fermented for 14 days showed maximum activity against the bacterial strains. Its ethyl acetate extract was found to be the most effective upon sequential solvent extraction of the 14-day Kombucha. This potent ethyl acetate extract was then subjected to thin layer chromatography for further purification of antibacterial ingredients which led to the isolation of an active polyphenolic fraction.
Catechin and isorhamnetin were detected as the major antibacterial compounds present in this polyphenolic fraction of Kombucha by High Performance Liquid Chromatography. Catechin, one of the primary antibacterial polyphenols in tea was also found to be present in Kombucha. But isorhamnetin is not reported to be present in tea, which may thereby suggest the role of fermentation process of black tea for its production in Kombucha. This is the first report on the presence of isorhamnetin in Kombucha. The scientists concluded that Kombucha can be used as a potent antibacterial agent against entero-pathogenic bacterial infections, which mainly is attributed to its polyphenolic content.
Kombucha Reduces Blood Pressure
In recent years, the consumption of herbal infusions around the world has increased due to their beneficial health effects. These beverages are prepared by placing a small amount of the selected plant material in freshly boiled water, allowing the preparation to steep for a short period of time. Although herbal infusions do not have any particular nutritional value, they represent an important source of bioactive compounds such as polyphenols. It has been shown that these compounds can act by diverse mechanisms providing significant protection against chronic diseases. For example, the consumption of some herbal polyphenols with antioxidant activity may regulate hypertension through inhibition of the angiotensin-converting enzyme (ACE), a key component in the renin-angiotensin aldosterone system which regulates blood pressure.
A recent study has demonstrated that fermentation of Litsea glaucescens and Eucalyptus camaldulensis infusions with kombucha consortium modifies their concentration of phenolic compounds, and their antioxidant and antihypertensive activities. Fermented beverages exhibited increased free radical scavenging activities. Additionally, it is interesting to note that E. camaldulensis and L. glaucescens can be considered as natural sources of biocompounds with antihypertensive potential (especially the latter) either as infusions or fermented beverages.
Foot in Mouth Disease
The foot and mouth disease virus (FMD) is sensitive to acids and can be inactivated by exposure to low pH conditions. Spraying animals at risk of infection with suspensions of acid-forming microorganisms has been identified as a potential strategy for preventing FMD. Kombucha is one of the most strongly acid-forming symbiotic probiotics and could thus be an effective agent with which to implement this strategy. Moreover, certain Chinese herbal extracts are known to have broad-spectrum antiviral effects. Chinese herbal kombucha can be prepared by fermenting Chinese herbal extracts with a kombucha culture. Previous studies demonstrated that Chinese herbal kombucha prepared in this way efficiently inhibits FMD replication in vitro.
To assess the inhibitory effects of Chinese herbal kombucha against FMD in vitro, swine challenged by intramuscular injection with the FMD. After treatment with Chinese herbal kombucha were partially protected against infection, as demonstrated by a lack of clinical symptoms and qRT-PCR analysis. In a large-scale field trial, spraying cattle in an FMD outbreak zone with kombucha protected against infection. Chinese herbal kombucha may be a useful probiotic agent for managing FMD outbreaks.
What about alternate Kombuchas?
Black tea infusion is the common substrate for preparing kombucha; however other sources such as oak leaves infusions can be used for the same purpose. Almost any white oak species have been used for medicinal applications by some ethnic groups in Mexico and could be also suitable for preparing kombucha analogues from oak (KAO).
A recent study was undertaken to investigate the antioxidant activity and anti-inflammatory effects of KAO by examining its modulation ability on macrophage derived TNF-alpha and IL-6. Herbal infusions from oak and black tea were fermented by kombucha consortium during seven days at 28C.
Levels of pro-inflammatory cytokines IL-6 and TNF-alpha were significantly reduced by the sample treatment of KAO. Likewise, NO production was lower in treatment with kombucha and KAO compared with LPS-stimulated macrophages. Fermented beverages of oak effectively down-regulated the production of NO, while pro-inflammatory cytokines (TNF-alpha and IL-6) in macrophages were stimulated with LPS. Additionally, phytochemical compounds present in KAO decreased oxidative stress.
The take home message is that kombucha made from oak leaves is anti-inflammatory and because of the polyphenols, a potent antioxidant.
Kefir
Kefir is made of small cauliflower floret-like grains added to the fresh milk. The grains are a mixture of yeasts and lactic acid bacteria within a polysaccharide and protein matrix, in a symbiotic community. The main ingredients of kefir are lactic acid, ethanol and CO2. The components of kefir complex are involved in the synthesis of anticancer bioactive components including peptides, polysaccharides and sphingolipids, playing vital roles in different signalling pathways and biological cell processes such as apoptosis, proliferation and transformation. Therefore, kefir can act as an effective agent in cancer treatment and prevention.
Kefir is acidic, partly effervescent, slightly alcoholic, milk foamy and viscous beverage with a uniform creamy and elastic consistency and sour taste, which can be easily digested. It is made from the fermentation of both traditional and commercial shapes of kefir grains with any type of semi-skimmed or skimmed pasteurized milk (got, sheep, cow, camel, buffalo).
Kefir grains composed of different microflora that is accumulating on matrix polysaccharide and protein, including lactic acid bacteria (Lactobacillus paracasei, Lactobacillus kefiri, Lactobacillus parabuchneri and Acetobacter lovaniensis) and yeast such as Saccharomyces cerevisiae and Kluyveromyces lactis. The bacteria convert the lactose to lactic acid, decreasing the milk pH, and yeasts produce ethanol and CO2 from lactic acid.
In terms of nutritional value, kefir contains at least 2.7% of protein, 0.6% of lactic acid and less than 10% of fat. Kefir is a rich source of vitamins (carotene, vitamins A, K, B1, B2, B5, C, B12 and folic acid) and amino acids (ammonia, serine, lysine, alanine, threonine, tryptophan, valine, lysine, methionine, phenylalanine and isoleucine) and mineral compositions (Mg, Ca, P, Zn, Cu, Mn, Fe, Co and Mo). It is important to note that the quality of the milk used in the process, preparation method and the presenting microorganisms in the kefir grains determine the quantity and the type of vitamin and mineral compositions.
Kefir is a traditional fermented milk containing over 50 species of probiotic microorganisms, consisting of lactic acid bacteria, yeast, and acetic acid bacteria. According to the Codex Standard for Fermented Milks (www.codexalimentarius.net), kefir is defined as fermented milk prepared from a unique starter culture known as kefir grains, which contains lactic acid bacteria such as Lactobacillus kefiri; members of the genera Leuconostoc and Lactococcus; acetic acid bacteria, and the lactose-fermenting (Kluyveromyces marxianus) and non-fermenting yeasts (Saccharomyces unisporus, Saccharomyces cerevisiae, and Saccharomyces exiguus). Many beneficial effects have been reported of both kefir and these microorganisms individually, including cholesterol-lowering effects, regulation of blood pressure, antitumor effects, wound healing, immunomodulatory effects, anti-allergenic effects, improving liver function, anti-diabetic effects, and anti-obesity effects.
Intestinal microbiota encompass a large variety of microorganisms located in the human intestinal tract with at least 1014 microbial cells originating from up to 1,000 different species. Recent studies have emphasized that the gut microbiota is not only composed of prokaryotic but also eukaryotic organisms, representing the gut mycobiota. Both the microbiota and mycobiota play critical roles in immunity, energy homeostasis, and digestion, as well as in the pathogenesis of certain systemic diseases.
Despite the numerous reviews on the multitude of beneficial health effects of kefir, there has been no systemic review conducted on the direct effect of the consumption of kefir and its microorganisms to modulate the host gut microbiota. In addition, the key attribute of kefir that sets it apart from other fermented milk products is yeast fermentation.
Modulation of Host Gut Microbiota and Mycobiota by Kefir and its Microorganisms
Along with the increasing recognition of the gut microbiota in disease and health status of the host in the last few decades, kefir and its microorganisms have been investigated for their potential to positively modulate the host gut microbiota. The early phase of this research focused on traditional culture methods to study the gut microbiota, which have been gradually replaced with targeted metagenomics approaches such as quantitative real-time polymerase chain reaction (PCR) and semi-targeted diversity analysis tools, including PCR denaturing gradient gel electrophoresis. More recently, untargeted metagenomics approaches have been introduced, including next-generation sequencing technology, which has helped to reveal many interesting and novel features of kefir.
Boosting the Good Guys!
The essential beneficial health effects of kefir and its microbiota can be attributed to their ability to increase the populations of beneficial microorganisms such as Lactobacillus, Lactococcus, and Bifidobacterium in the host gut. This effect is largely attributed to the introduction of kefir lactic acid bacterial species or strains into the host gastrointestinal tract. Considering that kefir contains very high levels of lactic acid bacteria, ranging from 8 to 10 log CFU/ml, and their excellent survivability and colonization properties, it is not surprising that kefir can increase the lactic acid bacterial population in the host.
Increasing Bifidobacterium
The increase of Bifidobacterium could be attributable to another mechanism by which the growth of resident Bifidobacterium in the host gut is promoted, because the presence of Bifidobacterium in kefir is not consistent among kefir grains – although Bifidobacterium has been detected in some kefir samples or added intentionally into kefir for improving the functionality. Indeed, research found that kefiran, the major exopolysaccharide in kefir, showed a bifidogenic effect in an animal model, suggesting that kefir-originated bioactive compounds could promote the indigenous Bifidobacterium population. It is known that kefiran administration increased the number of goblet cells which produce mucin on the surface of the intestinal lumen. Increased mucin availability in the intestine could result in the bifidogenic effect by kefiran, as mucin is a well-known nutritional source for Bifidobacterium.
Killing the Bad Guys
This phenomenon of lactobacilli-Enterobacteriaceae antagonism is a well-established example of gut microbial interaction, in which as the proportion of lactobacilli in the host gut increases, the population of Enterobacteriaceae decreases, and vice versa. As enriched lactic acid bacteria acidify the host gut by producing a variety of organic acids, this provides an unfavorable environment for acid-sensitive Enterobacteriaceae. In addition, kefir lactic acid bacteria compete with Enterobacteriaceae for nutrition and adhesion sites and produce a bacteriocin or antimicrobial exopolysaccharides against them. Other opportunistic pathogens such as Clostridium, Pasteurella, Flexispira, and Bacteroides are also inhibited by the consumption of kefir and its constituent microorganisms.
The Overall Effect of Keifer on the Gut
Overall, research concludes that kefir has broad and significant impacts on the gut bacterial population. It is noteworthy that although single probiotic agents generally colonize the host intestine, changes of the gut microbiota are not always guaranteed as a consequence. Given the multiple advantages of kefir to host health, powerful improvement of the gut microbiota by kefir consumption could promote its reputation as a high-functional probiotic food.
Link between the modulatory effect of kefir on the host gut microbiota and health benefits
It is well known that the gut microbiota is a virtual organ system that is important for the maintenance of health and well-being. Dysbiosis in this consortium induced impaired host homeostasis, which ultimately led to the emergence of clinical diseases. We have here provided a review on the emerging evidence of kefir to improve gut microbiota by increasing beneficial and decreasing harmful microbiota. In addition, many studies have reported the beneficial health effects of kefir consumption in the host, which have been experimentally and clinically demonstrated. A number of studies have suggested a relationship between these observed health effects and modulation of the intestinal microbiota.
Keifer may Reduce Obesity
For example, kefir consumption was found to prevent the development of obesity and non-alcoholic fatty liver diseases in high-fat diet-fed mice, based on a significant decrease in body weight gain, adiposity, and hepatic accumulation of lipid droplets. Moreover, correlation analysis indicated that these effects were significantly related to the kefir-induced increase in the populations of Lactobacillus and Candida, which promoted fatty acid oxidation in the adipose tissues and liver. In addition, Lactobacillus kefiri isolated from the same kefir grain increased the population of Lactobacillus in high-fat diet-fed mice, and prevented obesity by dual functions, including direct reduction of cholesterol in the lumen and upregulation of fatty acid oxidation in adipose tissues. In humans, researchers found that kefir consumption improved the serum lipid profile in overweight or obese women, which led to several hypotheses such as that kefir microorganisms in the gut might produce short-chain fatty acids and bile salt hydrolases, assimilate the exogenous cholesterol, or regulate gene expression to alter systemic lipid metabolism.
Kefir helps Obesity by Boosting Akkermansia
Physiological properties of water-soluble exopolysaccharides (EPS) and residues after EPS removal (Res) from the probiotic kefir were determined in high-fat (HF) diet-fed mice. EPS solutions showed rheological properties and lower viscosity compared to those of β-glucan (BG). EPS significantly suppressed the adipogenesis of preadipocytes in a dose-dependent manner. Mice were fed HF diets containing 5% EPS, 5% BG, 8% Res, or 5% microcrystalline cellulose (control) for 4 weeks.
Compared with the control, EPS supplementation significantly reduced HF diet-induced body weight gain, adipose tissue weight, and plasma very-low-density lipoprotein cholesterol concentration (P < 0.05). Res and BG significantly reduced body weight gain; however, reduction in adipose tissue weight was not statistically significant, suggesting that the antiobesity effect of EPS occurs due to viscosity and an additional factor.
The bottom line is that EPS from kefir supplementation significantly enhanced abundance of Akkermansia spp. in feces. This indicates that EPS shows significant antiobesity effects possibly via intestinal microbiota alterations.
Kefir and Cancer
In recent studies, the role of probiotics in health care is getting more attention and has been shown that lactic acid bacteria (LAB) as probiotics have a therapeutic effect in different diseases such as rheumatoid arthritis and cancer. Previous studies suggest that the probiotics, especially LAB, in addition to inducing apoptosis, have different anticancer properties including anti-proliferative, anti-inflammatory, antioxidative and anti-mutagenic effects.
Evidence shows the main polysaccharide of kefir, kefiran, has very important physicochemical properties that increase the viscosity and viscoelasticity of acid milk gels, and kefiran can improve the rheological properties and increase the viscosity. In addition, kefiran can be used as an antioxidant, anti-tumor and antimicrobial agent. On the other hand, kefir has positive effects on the immune system and cholesterol metabolism, improvement of bone health and lactose tolerance. Consequently, it is favorable that kefir intake may have a potential role in cancer prevention and treatment.
- Kefir intake decreases the secretion of TGF-α, TGF-β and Bcl2 and increases the secretion of bax leading to induction of apoptosis.
- Active peptides of kefir induce ROS-mediated apoptosis and activate Ca−/Mg−-dependent endonucleases for DNA cleavage.
- Low secretion of TGF-α and TGF-β induces the antiproliferative effect in cancerous cells.
- Sphingomyelins in kefir increase secretion of interferon-β, an anti-proliferative cytokine.
Anti‑carcinogenic effect of Kefir
Two mechanisms through which kefir induces anti-carcinogenic effect are as follows
Reducing Constipation and Oxidation
In addition, scientists demonstrated the constipation-alleviating effects of kefir, suggesting that the decreased proportion of members of the genus Clostridium by Lactobacillus kefiranofaciens may play a role in improving the defecation of mice. With respect to antioxidative effects, researchers proved that the administration of Lactobacillus plantarum YW11 from kefir increased the short-chain fatty acid-producing genera Blautia, Butyricicoccus, and Allobaculum, resulting in an increased level of short-chain fatty acids in the gut. This was significantly correlated with reduced oxidative stresses in a D-galactose-induced aging mouse model. In addition, scientists found that Lactobacillus plantarum MA2 from kefir successfully colonized the murine gut, decreased the serum and hepatic malondialdehyde levels, and increased the antioxidative enzyme activities, thereby exerting antioxidative effects.
Kefir-Fermented Sheep's Milk
Fermented milks are a source of bioactive peptides and may be considered as functional foods. Among these, sheep's milk fermented with kefir has not been widely studied and its most relevant properties need to be more thoroughly characterized. A study was set out to investigate and evaluate the antioxidant and antimicrobial properties of peptides from fermented sheep's milk in Brazil when produced by using kefir.
The chemical and microbiological composition of the sheep's milk before and after the fermentation was evaluated. The changes in the fermented milk and the peptides extracted before the fermentation and in the fermented milk during its shelf life were verified. The antimicrobial and antioxidant activities of the peptides from the fermented milk were evaluated and identified according to the literature. The physicochemical properties and mineral profile of the fermented milk were like those of fresh milk.
A high antioxidant activity was observed in the peptides extracted from fermented milk (3.125 mg/mL) on the 28th day of storage. Two fractions displayed efficient radical scavenging properties. At least 11 peptides distributed in the different fractions were identified by tandem mass spectrometry. This sheep's milk fermented by Brazilian kefir grains, which has antioxidant and antimicrobial activities and probiotic microorganisms, is a good candidate for further investigation as a source for bioactive peptides. The fermentation process was thus a means by which to produce potential bioactive peptides.
Helping Constipation
Constipation is a serious problem for persons with mental and physical disabilities in Japan. However, prophylaxis is extremely difficult because the major causes of constipation in these individuals are related to their mental and physical disabilities. Constipation can be successfully treated with glycerol enemas (GEs) and other treatments. As constipation is a lifetime issue for these persons, dietary regimens to prevent constipation can be important.
A study evaluated the probiotic effects of kefir-fermented milk for preventing constipation in 42 persons with mental and physical disabilities. The participants were administered 2 g of lyophilized kefir with each meal for 12 weeks and their bowel movements, the administration of GE and other aperients, and stool shape were recorded.
The intake of kefir significantly reduced constipation, compared with the baseline status. Some individuals showed complete relief of constipation, whereas others showed no effect. Basically, despite individual variations, consuming kefir daily could prevent constipation.
Saurkraut
One food group that has a long tradition of consumption by a variety of human populations is fermented food. According to researchers fermentation produces a wide range of flavors and aromas but also enriches food with proteins, vitamins, and essential amino and fatty acids and leads to a detoxification of food during the fermentation process.
Apart from fermented drinks and sauces, another classical approach is the fermentation of vegetables. In the case of cabbage, this leads to sauerkraut. Sauerkraut is one of the most common and oldest forms of preserved cabbage (Brassica oleracea convar capitata var sabauda L) or pointed cabbage (Brassica oleracea var capitata f alba). It is produced by the process of malolactic fermentation and can be traced back as a food source to the 4th century BC.3 Sauerkraut contains a large quantity of lactic acid; vitamins A, B, C, and K; and minerals and has few calories (about 80 kJ/100g). Even today in Germany, approximately 200 000 tons of cabbage are processed into sauerkraut. Between 1975 and 1980, the per capita use of sauerkraut in Germany stayed constant at 2.0 to 2.1 kg per year.3,4 Sauerkraut is also very popular in the Untied States and France, where it is also known as “German Kraut” or “Cassoulet.” Hippocrates described sauerkraut as a health food and medicinal remedy in his writing. The Romans have also valued the beneficial effect of sauerkraut. The writer Plinius Secundus wrote, “The cabbage helps to provide plenty of milk for breastfeeding mothers, it helps for cloudy eyes, positively affects headaches and is supposed to work as a cure after alcohol consumption.”5 Sauerkraut was one of the major foods in seafaring due to its high vitamin content and was used to counteract scurvy.6 In addition to these rather generally described health effects, scientific research assessed the effects and efficacy of sauerkraut. Research can be traced back to the early 20th century.
Sauerkraut Juice Kills Cancer
White cabbage is one of the most important vegetables grown both in Poland and worldwide. Cabbage contains considerable amounts of bioactive compounds such as glucosinolates, vitamin C, carotenoids, and polyphenols. Some experiments indicate that vegetables from organic production contain more bioactive compounds than those from conventional production, however, only a few studies have been conducted on cruciferous plants.
The recent study has proved that organic fresh cabbage, compared to the conventional one, contained significantly less total flavonoids in both years of experiments (3.95 ± 0.21 mg/100 g FW and 3.71 ± 0.33 mg/100 g FW), several flavonoid compounds, total chlorophylls (1.51 ± 0.17 mg/100 g FW and 1.30 ± 0.22 mg/100 g FW) carotenoids, nitrites (0.55 ± 0.04 mg/kg FW and 0.45 ± 0.02 mg/kg FW), and nitrates (0.50 ± 0.13 g/kg FW and 0.47 ± 0.11 g/kg FW).
The organic sauerkraut juice, compared to the conventional one, contained significantly more total polyphenols (5.39 ± 0.22 mg/100 g FW and 9.05 ± 1.10 mg/100 g FW) as well as several flavonoids. Only CONV sauerkraut juice produced with the highest N level of fertilization induced a statistical significant increase of the level of necrosis of human stomach gastric adenocarcinoma cell line AGS.
Experiments found that high levels of glucosinolates, ascorbigen, and ascorbic acid decrease DNA damage and cell mutation rate in cancer patients, and sauerkraut is known to have a high content of these compounds. However, the level of concentration strongly depends on the fermentation conditions of the cabbage. According to researchers, producing cabbage at low-salt concentration improved ascorbigen content, with the highest concentration being observed in low-sodium (0.5% NaCl) sauerkraut produced from cabbage cultivated in winter using natural fermentation.
Ascorbic acid content, on the other hand, was found to be higher in cabbage cultivated in summer, with fermentation reducing the content. This is supported by the studies of other researchers However, inhibition of enzymatic markers in the liver might not be seen as an indicator for anticarcinogenic activity, even if markers in the kidney show enhanced activity, which might be due to interaction effects.
Thus, the evidence base of sauerkraut for cancer currently seems to be inconclusive. This is even more questionable when considering the results of earlier research that found sauerkraut to be a risk factor for cancer. Apart from cancer-related aspects, different types of fermentation processes might also explain the results of the CASS-CHOU study on mesenteric angina, which also found significant differences between the sauerkraut products in that study.
Beer
Beer is one of the most frequently consumed alcoholic beverages in the world. Beer consumption ranks first in Europe, slightly above wine consumption, according to the World Health Organization and third amongst alcoholic beverage preferences in North America. Archaeological findings show that Chinese villagers brewed fermented alcoholic drinks as far back as 7000 BC on a small individual scale, with a production process and methods similar to those of ancient Egypt and Mesopotamia. Throughout human history, products, ingredients, procedures, and techniques have evolved due to technological advances and the implementation of industrialized processes further enhancing the long history of beer as a part of the human diet.
During the last two decades, scientific evidence has suggested that moderate consumption of alcoholic beverages has positive outcomes on different aspects of cardiovascular risk, as evidenced by Nogueira et al. who correlated regular daily intake of 330 ml of beer with positive changes in insulin sensitivity and lipid profiles. Fermented beverages have also shown positive associations with different cardiovascular disease endpoints such as coronary heart disease, peripheral arterial disease, chronic heart failure, and stroke in which regular moderate consumption of alcohol reduced the prevalence of adverse events, and fermented beverages have shown anti-inflammatory properties; these findings may explain the benefits of regular and moderate alcohol intake on cardiovascular disease risk.
Polyphenolic Compounds in Beer
Beer contains amino acids, carbohydrates, vitamins, minerals, and polyphenols. As mentioned above, beer contains a diversity of polyphenols mainly derived from hops and malt. Moreover, during the beer fermentation process, a resin produced by hops that contains monoacylphlorogucinols is converted into bitter acids such as humulones and isohumulones. These molecules act as bioactive antioxidants and provide additional beneficial effects Malt contains many free and total (bound) polyphenolic compounds; according to composition analysis using a liquid chromatography-antioxidant technique before and after fermentation, the concentrations of polyphenolic compounds may be increased by up to threefold after the fermentation process.
The main polyphenolic compounds present in beer are sinapic, ferulic, and caffeic acids. Vanillic acids are present in bound and unbound forms while 4-hydroxyphenylacetic and p-coumaric acids are present as free forms.
Beer and Menopause
Several intervention studies have evaluated the effects of beer and menopause. An 8-week, randomized, double-blind, cross-over trial showed that consuming 8-prenylnaringenin (8-PN), a characteristic polyphenol from hops and beer, resulted in a significant reduction in menopause symptoms and discomforts. Vasomotor symptoms are believed to be caused by a slight increase in body temperature in conjunction with a smaller thermo-neutral zone.
These processes are controlled by a region of the anterior hypothalamus called the thermoregulatory nucleus. This area responds to sex hormones as shown by experimental models with ovariectomized rats. These rats presented significant differences in body temperature compared to a unovariectomized control group, and the differences reversed when the rats were treated with estrogens or clonidine, an alpha adrenoceptor used for vasomotor symptom treatment, suggesting that temperature irregularities in menopause may be due to changes in the sex hormone regulatory system. In the same animal model, low doses of approximately 400 μg/kg/day of 8-prenylnaringenin were also able to alleviate menopausal vasomotor symptoms.
8-prenylnaringenin binds to both alpha and beta estrogen receptors (ER).
The effect of 8-prenylnaringenin may be explained by its strong affinity for both alpha and beta estrogen receptors (ER). The binding of 8-PN and the consequent activation of ERs lead to the stimulation of alkaline phosphatase activity and upregulate the activity of progesterone receptors and presenelin-2, both of which are estrogen-stimulated genes. In addition, low doses of 8-prenylnaringenin increase the libido of menopausal women.
The take home message
Alcohol-free beer could provide women with all the same possible benefits, without the risk of gastrointestinal pathologies and cancer that frequent alcohol consumption represents to health.
References
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Beer Polyphenols and Menopause: Effects and Mechanisms—A Review of Current Knowledge Berner Andrée Sandoval-Ramírez, Rosa M. Lamuela-Raventós, Ramon Estruch, Gemma Sasot, Monica Doménech, Anna Tresserra-Rimbau Oxid Med Cell Longev. 2017; 2017: 4749131