Fermented foods, such as sauerkraut and kombucha, have become popular for health reasons. I have made my own sauerkraut in the past and have recently made the tasty, fermented Korean side dish, kimchi. I did it not only for the taste but also for the hope that the bacteria responsible for the fermentation of the cabbage — lactic acid bacteria (LAB) — would contribute to the diversity of my gut microbiota.
As a research scientist in the field of bacterial pathogenesis, this made sense to me. Now that I have started blogging about health and fitness and have been writing more in depth articles about health related topics, I started wondering what research has been done on the health benefits of fermented foods. Can the bacteria in fermented foods even survive the harsh conditions of the human gastrointestinal (GI) tract, particularly the stomach?
I was amazed to learn that the fermentation of food has been used by humans for thousands of years as a way to preserve foods, and that the health benefits go beyond their microorganisms (don’t worry, citations are provided below). The fermentation process enhances the nutritional quality of food by contributing beneficial compounds such as vitamins, and by increasing the bioavailability of minerals. Probiotics, including those found in kimchi, have a range of positive effects on health, including the improvement of various intestinal inflammatory conditions, positive impacts on the immune system and even weight loss, and can alter the composition of the gut microbiome.
However, these effects mostly depend on whether the bacteria actually make it in sufficient numbers to the colon. And let me tell you, the journey to the colon is one harsh and dangerous ride!
What are fermented foods?
Fermentation is a mostly anaerobic process, meaning without oxygen, carried out by microorganisms or cells. These microorganisms convert sugars, such as glucose, into other compounds, such as alcohol, to produce energy to fuel their metabolism. Bacteria and yeasts — which undergo lactic acid fermentation and ethanol fermentation, respectively — are used in the fermentation of foods. The unique flavours and textures of fermented foods are due to the different species of bacteria and yeast used.
Humans have fermented foods for thousands of years throughout the world, and many dishes are unique to specific ethnic groups.1 Not only does the fermentation of foods add flavour and texture, but fermentation can also improve its shelf-life and may have been initially used to preserve fruits and vegetables during times of scarcity.2 The fermentation of food can occur spontaneously by the natural LAB surface microflora or by the use of a starter culture.3
Types of fermented foods
Lactic acid bacteria are the main bacteria in the production of fermented dairy products, such as yoghurt, cheese and kefir milk. They make lactic acid from lactose, the main sugar in milk. This increases acidity and makes life difficult for other microorganisms. The most common LAB involved in the fermentation of dairy are members of the genera Lactobacillus, Streptococcus, Leuonostoc, Enterococcus, and Lactococcus. Bifidobacteria are also included in fermented milk products.4 Most yoghurt, the fermented dairy product people know best, is produced with a culture of L. delbrueckii subp. bulgaricus and S. thermophiles.5
During the fermentation of dairy, many beneficial compounds are produced or increased by the metabolic activity of LAB, propionibacteria, yeast and mould, such as vitamin B-12, folic acid and biotin.6 Conjugated linoleic acid (CLA), a fatty acid with reported health benefits including fat loss, is also increased in fermented milk7 (I have previously blogged about CLA and found the mechanism by which it causes fat loss somewhat concerning, as it may damage surrounding cells, increase fatty deposits in the liver, and make blood lipids more prone to atherosclerosis aka hardening of the arteries.) Bioactive peptides with reported antihypertensive, antimicrobial, antioxidative, and immune-modulatory activities are also released by the activity of LAB in fermented milk products.8
Another potentially beneficial compound in fermented dairy is the non-digestible carbohydrate galacto-oligosaccharide, which is synthesized by LAB from lactose. Galacto-oligosaccharide has a prebiotic effect on intestinal microbiota, meaning it probably promotes the growth of beneficial bacteria in the gut.9
In addition, yoghurt in particular is a rich source of dietary minerals, including calcium, magnesium, potassium, phosphorus, and zinc.10 The concentration of these minerals is nearly 50% higher in yoghurt than in milk,11 and they are easier to digest and absorb: the acidic environment created by fermentation with LAB can enhance the bioavailability of these minerals.
And there’s more: yoghurt is also an excellent source of essential amino acids. The amount of free amino acids is increased due to the pre-digestion of milk proteins by the activity of bacterial cultures, allowing for better protein digestibility.12
Large cohort studies conducted in the Netherlands, Sweden, and Denmark found that fermented milk products were significantly associated with decreased disease states. These disease states include bladder cancer, cardiovascular disease, and periondontitis.13-15 Based on these findings, I am going to enjoy my Greek yoghurt for breakfast even more now!
Although harmful compounds, including mycotoxins and biogenic amines, can contaminate fermented dairy products, strict regulatory standards are set by international agencies for the monitoring of these substances. Fortunately, reliable methods to detect these compounds have been developed.16-19
The fermentation by LAB is recognized as a simple and valuable method to maintain and enhance the safety, nutritional quality, and the shelf life of vegetables, particularly when access to fresh vegetables is limited. The most commercially significant fermented vegetables are:
- Cabbage, in the form of sauerkraut and kimchi
- Cucumbers, in the form of pickles
Typically the fermentation of vegetables occurs spontaneously just from the bacteria already present on the surface, but starter cultures can also be used. Starter cultures speed up the fermentation process, ensure reliability of the final product, prevent the risk of fermentation failure, and assist with the inhibition of spoilage and pathogenic microorganisms.20
Lactic fermentation has been shown to enhance the nutritional value of vegetables. When used with maize, soybeans, and sorghum (a grain), it reduces phytate content, a well-known inhibitor of iron and zinc absorption.21 It has also been shown that fermentation of maize enhances the bioavailability of iron.22 A 2015 study published in the European Journal of Nutrition found that the reason for the increased bioavailability of iron in lactic-fermented vegetables compared to fresh vegetables is due to an increase in the concentration of hydrated ferric iron (Fe3+) which may be more favourable for iron absorption.23
It is clear to me that the fermentation process boosts the nutritional quality of foods. Now, what about the impact of the actual bacteria carrying out the fermentation?
The impact of fermented foods and probiotics on the microbiome
Understanding of the importance of the human gut microbiota and microbiome to health and disease has expanded rapidly with the advances in DNA sequencing technology. (The gut microbiota is the microorganisms that inhabit the gut, while the gut microbiome is the total genome content of the gut microbiota.) Research in this field has focused on what role this complex bacterial community plays in human health and disease, and how it can be altered.
Diet is one of the main influences on the human gut microbiota.24, 25 Many food-ingested bacteria can temporarily join the gut microbiota, possibly affecting the behaviour of the resident gut microbial community. These food-ingested bacteria can be found in great numbers in fermented foods and as probiotics. Probiotics are defined as live microorganisms in food that confer a health benefit on the host.26 Here on SBM, Scott Gavura concluded, “There’s reasonably good evidence that probiotics, when taken with antibiotics, will reduce the risk of antibiotic-associated diarrhea.” In her review of Martin Blaser’s Missing Microbes, Dr. Harriet Hall wrote, “This is exciting stuff! I wish I could be alive 100 years from now to see how research into the microbiome will change the practice of medicine.”
The bacteria in fermented foods are considered probiotics.
Recent research suggests that the human gut microbiome is made up of a core population of bacteria and a variable commensal community, and it seems that bacteria ingested via food contribute to this “variable microbiome”.27 As I have already mentioned, LAB are the most widely-used strains to ferment foods. While some LAB species are thought to be permanent inhabitants of the gastrointestinal (GI) tract, other species, such as L. plantarum, L. rhamonosus, and L. paracasei appear to be temporary colonizers.28 Some species of bifidobacteria, which are found in fermented dairy, are also typical members of the transient microbiota.29
A recent study in Scientific Reports directly compared the impact of fermented and non-fermented milk products on the gut microbiome of subjects with irritable bowel syndrome (IBS). The fermented milk product altered the species of the gut microbiota more than the non-fermented milk product. Additionally, consumption of the fermented milk product decreased the “pathobionts” Bilophila wadsworthia and Clostridium sp. HGF2.30 Pathobionts is a new term describing members of the resident microbiota that have disease-causing potential.31
Bacteria derived from food appear to be members of the variable human microbiome with the ability to alter the gut microbiome. But do the bacteria we ingest in common fermented foods, such as yoghurt (and my new favourite fermented food, kimchi) actually survive once we eat them? In other words, are common fermented foods a direct source of bacteria that contribute to our microbiome?
Can bacteria from fermented foods survive the human GI tract?
Before ingested bacteria can have a beneficial impact in the human intestinal system, they must first be able to survive within the food matrix, the nutrient and non-nutrient components of food plus their interactions at a molecular level. Many factors can affect probiotic viability in the food matrix, such as the acidity, oxygen availability, concentration of sugars, moisture content, and the storage temperature.32
Immediately after swallowing, these poor little microbes must be able to withstand the hostile environment of the human upper GI tract, which includes the mouth, esophagus, stomach, and duodenum (the first part of the small intestine). After being chewed and mixed with enzymes from saliva in the mouth, the bacteria from fermented foods then pass down the throat and esophagus and into the stomach. The stomach is an extremely acidic environment (pH <3) and contains destructive digestive enzymes, such as pepsin, which break down proteins into smaller amino acid building blocks. Most ingested bacteria will not survive this first part of the journey.
Those bacteria that do survive then enter the remainder of the small intestine, where the pH rises to over 6, but they are exposed to bile and many more digestive enzymes, including amylase (which breaks starches into simple sugars), lipase (which breaks down fats), and protease (which further breaks down proteins). Some bacterial strains can recover, and even grow in the small intestine, and these cells must then continue their journey on to the colon.33 Not only must these ingested bacteria be able to survive the human GI tract, they must also be able to adhere to the gut epithelial cells in order to have any beneficial effects.34, 35
Variation in the ability of probiotic strains to survive the human GI tract has been demonstrated. Studies subjecting various strains to conditions simulating the environment of the human GI tract found that strains of B. animalis, L. casei, L. rhamnosus and L. plantarum have the greatest resilience.33, 36-38
Since many of us are familiar with yoghurt as a fermented food, I wanted to know if the bacteria within commercial yoghurts actually survive this treacherous journey. A study of 15 healthy adult volunteers looked at the effect on the fecal bacterial community of probiotic LAB in commercial yoghurt.39 The subjects were divided into three groups: one group consuming 110 grams of yoghurt A, one group consuming 180ml of yoghurt B, and the third group consuming 90 grams of yoghurt C. Everyone ate one serving per day for 20 days. The labels of yoghurt A and B stated that these products contain a probiotic Lactobacillus strain, while yoghurt C did not state this on the label.
The probiotic strains were detected in the feces of subjects consuming yoghurt A and B for up to 28 days after the first day of consumption. This showed that probiotic strains in yoghurt survive the human GI tract. The study also detected changes in the populations of bacterial groups in the fecal microbiota in all three groups.
Another similar study of 36 subjects looked at the persistence of four probiotic strains from capsules, yoghurts, or cheese at a dose of 1.9–5.0 × 109 colony-forming units (CFUs). They found that all four probiotic strains survived the GI tract and could be detected in fecal samples following consumption in all subjects. Two strains endured better, with the highest quantities recovered in the fecal samples from the yoghurt group,40 so it does seem that probiotics present in yoghurt can survive the human GI tract provided that the bacteria are present in high enough numbers in the yoghurt to begin with.
How about the LAB in kimchi? One study found that L. plantarum KC21 isolated from kimchi showed acid and bile tolerance and the ability to adhere to human intestinal cells.41 Another found that subjects who consumed 300g/day of kimchi had significantly higher counts of fecal Lactobacillus species and Leuconostoc species during the kimchi intake period.42 As with the yoghurt, these results suggest that LAB will survive in your gut if it’s present in sufficient numbers in your kimchi in the first place.
Now let’s look at the clinical studies investigating the health benefits.
Clinical studies on the health benefits of probiotics and fermented foods
Many clinical studies have investigated the effect of probiotics on human health. The reported beneficial effects of probiotic consumption include improvement of constipation, diarrhea, and intestinal inflammatory conditions (such as Crohn’s disease, ulcerative colitis, irritable bowel syndrome, and necrotizing enterocolitis),43 and the prevention of allergic disease in infants.44, 45 Furthermore, supplementation with probiotics has been shown to positively enhance immune system function,46-48 improve the symptoms of lactose intolerance, and can prevent infection with pathogenic or disease causing microorganisms.49 One promising study recently published in The Journal of Allergy and Clinical Immunology showed possible alleviation of peanut allergy in children by coadministering probiotics with a peanut oral immunotherapy. Previous studies found that administration of probiotics or peanut oral immunotherapy alone did not have this effect.80
The mechanisms by which probiotics exert these influences are not yet clear. The cells lining the intestine, the intestinal epithelial cells, are an important part of the innate or non-specific immune system and act as a link to the adaptive or specific immune system. The intestinal epithelial cells are able to recognize many bacterial components and are the first point of contact for ingested microbes.50, 51 The latest research suggests several mechanisms by which probiotic microbiota may produce health effects:
- outcompeting bacterial pathogens
- preventing attachment of pathogens to host cells52-54
- strengthening the mucosal barrier55
- release of immune-cell-stimulating and anti-inflammatory molecules (cytokines)56, 57
- the production of antimicrobial substances, including organic acids, hydrogen peroxide, and bacteriocins (small strings of amino acids that inhibit the growth of other bacteria)58, 59
Probiotics can be in food or supplements, such as pills and capsules. In 2009 the global probiotic supplement market was worth about $1.5 billion USD60 and predicted to rise to $32.6 billion by 2014.61 The probiotic industry holds about a 10% share of the global functional food market.62
How many microorganisms do you have to eat to get a benefit?
Dosages of probiotics are measured in CFUs per serving: the number of cells able to grow from a single serving (food or capsule) in a petri dish. There seems to be agreement in the literature that, for health benefits to be achieved, a dosage of 108–109 CFUs is needed.63-65 That’s one hundred million to one billion per serving. Bacteria are small!
A 2013 study published in the Journal of Applied Microbiology found between 107 and 108 CFU/ml of Lactobacillus delbrueckii subsp. bulgaricus within a commercial brand of yoghurt (Activia® from Danone) — and most people probably eat more than a fifth of a teaspoon of yoghurt at a time.66 Other studies have also found that commercial yoghurts do contain enough Lactobacillus to confer potential health benefits.67
Does kimchi have health benefits too?
Let’s zoom in on kimchi. I am a big fan of this tasty fermented side dish, and have started getting into making it at home. After looking at the studies, I am even more enthusiastic!
Kimchi has been eaten in Korea for about 2,000 years. The most popular kimchi is baechu or Chinese cabbage kimchi, which is generally made by LAB fermentation of baechu cabbage, radish, green onion, red pepper powder, garlic, ginger and fermented seafoods.68 Most kimchi contains 107 – 109 CFUs/gram of LAB. The profile of LAB species in kimchi changes with the pH throughout the fermentation process. Leuconostoc mesenteroides is present during the early stages (pH 5.64–4.27) while Lactobacillus sakei dominates in the later stages of (pH 4.15).69 Other LAB contributing to kimchi fermentation include Leu. citreum, Leu. gasicomitatum, L. brevis, L. curvatus, L. plantarum, Lactococcus lactis, Pediociccus pentosaceus, Weissella confusa and W. koreensis.70, 71
Studies investigating the potential beneficial effects of the bacteria isolated from kimchi have found the following:
- One of the LAB strains isolated from kimchi was found to have potent antioxidative activity in vitro.72
- L. plantarum from kimchi has shown various immune-modulatory activities, such as the activation and stimulation of cytokine production in mouse macrophages,73, 74 and a variety of other immune-modulating activities.75, 76
- LAB from kimchi was found to have antiobesity effects in rats77, 78 and mice.78
- LAB isolated from kimchi has shown antimicrobial activities against a range of pathogenic bacteria.41, 79
So it appears that kimchi is more than just a delicious addition to my bibimbap.
Conclusion: Fermented foods probably deserve their healthful reputation
The bacteria in fermented dairy and vegetables can survive their perilous journey through the digestive tract. Once they are there, it’s clear that they have at least some positive effects on human health, ranging from the enhanced nutritional contents of the foods themselves, to alleviation of inflammatory bowel conditions, to restoring normal gut microbiota after antibiotics, to enhancement of the immune system, and possibly even weight loss. It would be nice to know more about the mechanisms of these effects — and maybe we will know soon, because it is currently a hot area of research. I will continue to enjoy fermented foods not only for their delicious tastes and textures, but also for the health benefits. Have some fun and have a go at making your own kimchi. It is absolutely worth the effort.
Lucy Shewell, PhD, is a research scientist in the field of molecular microbiology. Her current research focuses on bacterial toxins and their interactions with host cells. Her research has been published in leading scientific journals including The Proceedings of the National Academy of Sciences and Nature Communications. In her spare time, Dr. Shewell trains for and competes in multisport and endurance races, fuels her training and racing with practical, easy to prepare, and nutritious whole foods, and researching and writing articles on topics in health, nutrition, fitness and athletic performance using quality, peer-reviewed science.
- Farnworth ER (2008). Handbook of Fermented Functional Foods (CRC Press, Boca Raton, FL, USA). ISBN 9781420053265
- Rolle R & Satin M (2002). Basic requirements for the transfer of fermentation technologies to developing countries. International Journal of Food Microbiology 75(3):181-187. PMID 12036141
- J. Karovičová, Milan Drdák, Gabriel Greif, & Hybenová E (1999). The choice of strains of Lactobacillus species for the lactic acid fermentation of vegetable juices. European Food Research and Technology 210(1):53-56. DOI: 10.1007/s002170050532
- Quigley L, et al. (2011). Molecular approaches to analysing the microbial composition of raw milk and raw milk cheese. International Journal of Food Microbiology 150(2-3):81-94. PMID 21868118
- Donovan SM & Shamir R (2014). Introduction to the yogurt in nutrition initiative and the First Global Summit on the health effects of yogurt. The American Journal of Clinical Nutrition 99(5 Suppl):1209S-1211S. PMID 24646825
- Beermann C & Hartung J (2013). Physiological properties of milk ingredients released by fermentation. Food & Function 4(2):185-199. PMID 23111492
- Hennessy AA, et al. (2012). The production of conjugated alpha-linolenic, gamma-linolenic and stearidonic acids by strains of bifidobacteria and propionibacteria. Lipids 47(3):313-327. PMID 22160449
- Parvez S, Malik KA, Ah Kang S, & Kim HY (2006). Probiotics and their fermented food products are beneficial for health. Journal of Applied Microbiology 100(6):1171-1185. PMID 16696665
- Padilla B, et al. (2012). Evaluation of oligosaccharide synthesis from lactose and lactulose using beta-galactosidases from Kluyveromyces isolated from artisanal cheeses. Journal of Agricultural and Food Chemistry 60(20):5134-5141. PMID 22559148
- USDA ARS (2013). USDA national nutrient database for standard reference, release 26. Nutrient Data Laboratory homepage.
- Wang H, Livingston KA, Fox CS, Meigs JB, & Jacques PF (2013). Yogurt consumption is associated with better diet quality and metabolic profile in American men and women. Nutrition Research 33(1):18-26. PMID 23351406
- Adolfsson O, Meydani SN, & Russel RM (2004). Yogurt and gut function. The American Journal of Clinical Nutrition 80:245-256. PMID 15277142
- Keszei AP, Schouten LJ, Goldbohm RA, & van den Brandt PA (2010). Dairy intake and the risk of bladder cancer in the Netherlands Cohort Study on Diet and Cancer. American Journal of Epidemiology 171(4):436-446. PMID 20042437
- Sonestedt E, et al. (2011). Dairy products and its association with incidence of cardiovascular disease: the Malmo diet and cancer cohort. European journal of epidemiology 26(8):609-618. PMID 21660519
- Adegboye AR, et al. (2012). Intake of dairy products in relation to periodontitis in older Danish adults. Nutrients 4(9):1219-1229. PMID 23112910
- Siddappa V, Nanjegowda DK, & Viswanath P (2012). Occurrence of aflatoxin M(1) in some samples of UHT, raw & pasteurized milk from Indian states of Karnataka and Tamilnadu. Food and Chemical Toxicology 50(11):4158-4162. PMID 22939935
- Prandini A, et al. (2009). On the occurrence of aflatoxin M1 in milk and dairy products. Food and Chemical Toxicology 47(5):984-991. PMID 18037552
- Linares DM, Martin MC, Ladero V, Alvarez MA, & Fernandez M (2011). Biogenic amines in dairy products. Critical Reviews in Food Science and Nutrition 51(7):691-703. PMID 21793728
- Redruello B, et al. (2013). A fast, reliable, ultra high performance liquid chromatography method for the simultaneous determination of amino acids, biogenic amines and ammonium ions in cheese, using diethyl ethoxymethylenemalonate as a derivatising agent. Food Chemistry 139(1-4):1029-1035. PMID 23561206
- Buckenhuskes HJ (1997). Fermented vegetables. Food Microbiology: Fundamentals and Frontiers, eds Doyle PD, Beuchat LR, & Montville TJ (ASM Press, Washington, DC), 2nd Ed, pp 595-609. ISBN 9781555811174
- Bering S, et al. (2006). A lactic acid-fermented oat gruel increases non-haem iron absorption from a phytate-rich meal in healthy women of childbearing age. The British Journal of Nutrition 96(1):80-85. PMID 16869994
- Proulx AK & Reddy MB (2007). Fermentation and lactic acid addition enhance iron bioavailability of maize. Journal of Agricultural and Food Chemistry 55(7):2749-2754. PMID 17355139
- Scheers N, Rossander-Hulthen L, Torsdottir I, & Sandberg AS (2015). Increased iron bioavailability from lactic-fermented vegetables is likely an effect of promoting the formation of ferric iron (Fe). European Journal of Nutrition. PMID 25672527
- Flint HJ (2012). The impact of nutrition on the human microbiome. Nutrition Reviews 70 Suppl 1:S10-13. PMID 22861801
- Scott KP, Gratz SW, Sheridan PO, Flint HJ, & Duncan SH (2013). The influence of diet on the gut microbiota. Pharmacological Research: The Official Journal of the Italian Pharmacological Society 69(1):52-60. PMID 23147033
- FAO/WHO (2001). Report on Joint FAO/WHO Expert Consultation on Evaluation of Health and Nutritional Properties of Probiotics in Food Including Powder Milk with Live Lactic Acid Bacteria.
- Jalanka-Tuovinen J, et al. (2011). Intestinal microbiota in healthy adults: temporal analysis reveals individual and common core and relation to intestinal symptoms. PloS One 6(7):e23035. PMID 21829582
- Reuter G (2001). The Lactobacillus and Bifidobacterium microflora of the human intestine: composition and succession. Current Issues in Intestinal Microbiology 2(2):43-53. PMID 11721280
- Turroni F, et al. (2014). Molecular dialogue between the human gut microbiota and the host: a Lactobacillus and Bifidobacterium perspective. Cellular and Molecular Life Sciences: CMLS 71(2):183-203. PMID 23516017
- Veiga P, et al. (2014). Changes of the human gut microbiome induced by a fermented milk product. Scientific Reports 4:6328. PMID 25209713
- Round JL & Mazmanian SK (2009). The gut microbiota shapes intestinal immune responses during health and disease. Nature Reviews. Immunology 9(5):313-323. PMID 19343057
- Champagne CP, Ross RP, Saarela M, Hansen KF, & Charalampopoulos D (2011). Recommendations for the viability assessment of probiotics as concentrated cultures and in food matrices. International Journal of Food Microbiology 149(3):185-193. PMID 21803436
- Derrien M & van Hylckama Vlieg JE (2015). Fate, activity, and impact of ingested bacteria within the human gut microbiota. Trends in Microbiology 23(6):354-366. PMID 25840765
- Lee YK, et al. (2000). Quantitative approach in the study of adhesion of lactic acid bacteria to intestinal cells and their competition with enterobacteria. Applied and Environmental Microbiology 66(9):3692-3697. PMID 10966378
- Ouwehand AC, Tuomola EM, Lee YK, & Salminen S (2001). Microbial interactions to intestinal mucosal models. Methods in Enzymology 337:200-212. PMID 11398429
- van Bokhorst-van de Veen H, et al. (2012). Modulation of Lactobacillus plantarum gastrointestinal robustness by fermentation conditions enables identification of bacterial robustness markers. PloS One 7(7):e39053. PMID 22802934
- Marteau P, Minekus M, Havenaar R, & Huis in’t Veld JH (1997). Survival of lactic acid bacteria in a dynamic model of the stomach and small intestine: validation and the effects of bile. Journal of Dairy Science 80(6):1031-1037. PMID 9201571
- van Bokhorst-van de Veen H, van Swam I, Wels M, Bron PA, & Kleerebezem M (2012). Congruent strain specific intestinal persistence of Lactobacillus plantarum in an intestine-mimicking in vitro system and in human volunteers. PloS One 7(9):e44588. PMID 22970257
- Uyeno Y, Sekiguchi Y, & Kamagata Y (2008). Impact of consumption of probiotic lactobacilli-containing yogurt on microbial composition in human feces. International Journal of Food Microbiology 122(1-2):16-22. PMID 18077045
- Saxelin M, et al. (2010). Persistence of probiotic strains in the gastrointestinal tract when administered as capsules, yoghurt, or cheese. International Journal of Food Microbiology 144(2):293-300. PMID 21074284
- Lim SM & Im DS (2009). Screening and characterization of probiotic lactic acid bacteria isolated from Korean fermented foods. Journal of Microbiology and Biotechnology 19(2):178-186. PMID 19307768
- Lee KE, Choi UH, & Ji GE (1996). Effect of kimchi in intake on the composition of human large intestinal bacteria. Korean J Food Sci Technol 28:981-986. Abstract
- Vitetta L, Briskey D, Alford H, Hall S, & Coulson S (2014). Probiotics, prebiotics and the gastrointestinal tract in health and disease. Inflammopharmacology 22(3):135-154. PMID 24633989
- Kirjavainen PV, Arvola T, Salminen SJ, & Isolauri E (2002). Aberrant composition of gut microbiota of allergic infants: a target of bifidobacterial therapy at weaning? Gut 51(1):51-55. PMID 12077091
- Hattori K, et al. (2003). [Effects of administration of bifidobacteria on fecal microflora and clinical symptoms in infants with atopic dermatitis]. Arerugi = [Allergy] 52(1):20-30. PMID 12598719
- Isolauri E, Arvola T, Sutas Y, Moilanen E, & Salminen S (2000). Probiotics in the management of atopic eczema. Clinical and Experimental Allergy: Journal of the British Society for Allergy and Clinical Immunology 30(11):1604-1610. PMID 11069570
- Neish AS, et al. (2000). Prokaryotic regulation of epithelial responses by inhibition of IkappaB-alpha ubiquitination. Science 289(5484):1560-1563. PMID 10968793
- Schiffrin EJ, Brassart D, Servin AL, Rochat F, & Donnet-Hughes A (1997). Immune modulation of blood leukocytes in humans by lactic acid bacteria: criteria for strain selection. The American Journal of Clinical Nutrition 66(2):515S-520S. PMID 9250141
- Lee YK & Puong KY (2002). Competition for adhesion between probiotics and human gastrointestinal pathogens in the presence of carbohydrate. The British Journal of Nutrition 88 Suppl 1:S101-108. PMID 12215184
- Creagh EM & O’Neill LA (2006). TLRs, NLRs and RLRs: a trinity of pathogen sensors that co-operate in innate immunity. Trends in Immunology 27(8):352-357. PMID 16807108
- Hughes DT & Sperandio V (2008). Inter-kingdom signalling: communication between bacteria and their hosts. Nature Reviews. Microbiology 6(2):111-120. PMID 18197168
- Botic T, Klingberg TD, Weingartl H, & Cencic A (2007). A novel eukaryotic cell culture model to study antiviral activity of potential probiotic bacteria. International Journal of Food Microbiology 115(2):227-234. PMID 17261339
- Juntunen M, Kirjavainen PV, Ouwehand AC, Salminen SJ, & Isolauri E (2001). Adherence of probiotic bacteria to human intestinal mucus in healthy infants and during rotavirus infection. Clinical and Diagnostic Laboratory Immunology 8(2):293-296. PMID 11238211
- Resta-Lenert S & Barrett KE (2003). Live probiotics protect intestinal epithelial cells from the effects of infection with enteroinvasive Escherichia coli (EIEC). Gut 52(7):988-997. PMID 12801956
- Banasaz M, Norin E, Holma R, & Midtvedt T (2002). Increased enterocyte production in gnotobiotic rats mono-associated with Lactobacillus rhamnosus GG. Applied and Environmental Microbiology 68(6):3031-3034. PMID 12039764
- Deplancke B & Gaskins HR (2001). Microbial modulation of innate defense: goblet cells and the intestinal mucus layer. The American Journal of Clinical Nutrition 73(6):1131S-1141S. PMID 11393191
- Otte JM & Podolsky DK (2004). Functional modulation of enterocytes by gram-positive and gram-negative microorganisms. American Journal of Physiology. Gastrointestinal and Liver Physiology 286(4):G613-626. PMID 15010363
- O’Shea EF, et al. (2009). Characterization of enterocin- and salivaricin-producing lactic acid bacteria from the mammalian gastrointestinal tract. FEMS Microbiology Letters 291(1):24-34. PMID 19076236
- Pridmore RD, Pittet AC, Praplan F, & Cavadini C (2008). Hydrogen peroxide production by Lactobacillus johnsonii NCC 533 and its role in anti-Salmonella activity. FEMS Microbiology Letters 283(2):210-215. PMID 18435747
- Heller L (2009). Danisco breaks down probiotics market. (Nutra Ingredients, USA).
- Cook MT, Tzortzis G, Charalampopoulos D, & Khutoryanskiy VV (2012). Microencapsulation of probiotics for gastrointestinal delivery. Journal of Controlled Release: Official Journal of the Controlled Release Society 162(1):56-67. PMID 22698940
- Starling S (2009). Probiotics must meet Europe’s new health claim laws head on.
- Oliveira RP, et al. (2009). Effect of different prebiotics on the fermentation kinetics, probiotic survival and fatty acids profiles in nonfat symbiotic fermented milk. International Journal of Food Microbiology 128(3):467-472. PMID 19000641
- Reid G (2008). How science will help shape future clinical applications of probiotics. Clinical Infectious Diseases: An Official Publication of the Infectious Diseases Society of America 46 Suppl 2:S62-66; discussion S144-151. PMID 18181725
- Govender M, et al. (2014). A review of the advancements in probiotic delivery: Conventional vs. non-conventional formulations for intestinal flora supplementation. AAPS PharmSciTech 15(1):29-43. PMID 24222267
- Herbel SR, et al. (2013). Species-specific quantification of probiotic lactobacilli in yoghurt by quantitative real-time PCR. Journal of Applied Microbiology 115(6):1402-1410. PMID 24024971
- Dunlap BS, Yu H, & Elitsur Y (2009). The probiotic content of commercial yogurts in West Virginia. Clinical Pediatrics 48(5):522-527. PMID 19246412
- Park KY, Jeong JK, Lee YE, & Daily JW, 3rd (2014). Health benefits of kimchi (Korean fermented vegetables) as a probiotic food. Journal of Medicinal Food 17(1):6-20. PMID 24456350
- Lee D, Kim S, Cho J, & Kim J (2008). Microbial population dynamics and temperature changes during fermentation of kimjang kimchi. Journal of Microbiology 46(5):590-593. PMID 18974963
- Lee JS, et al. (2005). Analysis of kimchi microflora using denaturing gradient gel electrophoresis. International Journal of Food Microbiology 102(2):143-150. PMID 15992614
- Kim M & Chun J (2005). Bacterial community structure in kimchi, a Korean fermented vegetable food, as revealed by 16S rRNA gene analysis. International Journal of Food Microbiology 103(1):91-96. PMID 16084269
- Lee J, Hwang KT, Heo MS, Lee JH, & Park KY (2005). Resistance of Lactobacillus plantarum KCTC 3099 from Kimchi to oxidative stress. Journal of Medicinal Food 8(3):299-304. PMID 16176138
- Lee JH, Kweon DH, & Lee SC (2006). Isolation and characterization of an immunopotentiating factor from Lactobacillus plantarum in kimchi: assessment of immunostimulatory activities. . Food Sci Biotechnol 15:877-883. Abstract
- Hur HJ, Lee KW, & Lee HJ (2004). Production of nitric oxide, tumor necrosis factor-alpha and interleukin-6 by RAW264.7 macrophage cells treated with lactic acid bacteria isolated from kimchi. BioFactors 21(1-4):123-125. PMID 15630182
- Jang SE, et al. (2013). Lactobacillus plantarum HY7712 ameliorates cyclophosphamide-induced immunosuppression in mice. Journal of microbiology and biotechnology 23(3):414-421. PMID 23462016
- Chae OW, Shin KS, Chung H, & Choe TB (1998). Immunostimulation effects of mice fed with cell lysate of Lactobacillus plantarum isolated from kimchi. Korean J Biotech Bioeng 13:424-430. Article
- Kim NH, et al. (2008). Lipid profile lowering effect of Soypro fermented with lactic acid bacteria isolated from Kimchi in high-fat diet-induced obese rats. BioFactors 33(1):49-60. PMID 19276536
- Kwon JY, Cheigh HS, & Song YO (2004). Weight reduction and lipid lowering effects of kimchi lactic acid powder in rats fed high fat diets. Korean J Food Sci Technol 36:1014-1019. Article
- Ahn DK, Han TW, Shin HY, Jin IN, & Ghim SY (2003). Diversity and antibacterial activity of lactic acid bacteria isolated from kimchi. Korean J Microbiol Biotechnol 31:191-196. Abstract
- Tang, M., Ponsonby, A-L., Orsini, F., Tey, D., Robinson, M., Su, E. L., Licciardi, P., Burks, W., and Donath, S., (2015). Administration of a probiotic with peanut oral immunotherapy: A randomized trial. The Journal of Allergy and Clinical Immunology. 135 (3): 737-44.PMID 25592987