Most people consider kimchi, sauerkraut, kombucha, natto, miso, and other fermented foods synonymous with probiotics. The association is quite natural: Probiotics are live microbes that produce health benefits; fermented foods have live microbes and deliver health benefits; therefore, live microbes in fermented foods must be probiotics.
This logic is tempting to accept. It sounds right. After all, what else could explain why people who eat fermented foods resolve bloating, constipation, eczema, or reduced frequency of the common cold.
Still, the question remains whether fermented foods contain probiotics? Are the live microbes in fermented foods probiotics? To answer this let’s first define probiotics and compare them to microbes in fermented foods.
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What are probiotics?
The definition for probiotics put out in 2001 by a joint Food and Agriculture Organization of the United Nations/Whole Health Organization panel (1) and reaffirmed in 2013 (2) is still the most widely accepted version today. Defined, probiotics are, “live microorganisms that, when administered in adequate amounts, confer a health benefit on the host” (2).
Most probiotics are bacteria from two groups (genera), Bifidobacterium and Lactobacillus (3), while other probiotics are yeast (Sacchromyces boulardii). Microbes are defined by three levels of classification: genus, species, and strain.
In the case of Lactobacillus rhamnosus GG, the genus is Lactobacillus, the species, Lactobacillus rhamnosus, and the strain, Lactobacillus rhamnosus GG.
Naming probiotics always requires identification at the strain-specific level, because health effects for one species may not be the same for another species within the same strain. For example, health effects for Lactobacillus rhamnosus GG may be different for Lactobacillus rhamnosus XYZ, hypothetically.
Probiotic dietary supplements aren’t the only source of probiotics on the market. Other recognized probiotics sources are probiotic drugs, medical foods, fortified foods, probiotic skin care, and infant formula. There are even probiotics available for animals animal feed.
Benefits of probiotics
Broadly speaking, probiotics yield health benefits through one or more mechanisms:
- stimulating the immune system
- reducing inflammation
- displacing harmful bacteria
- enhancing barrier function along gut lining
Probiotics yield several health benefits such as reducing diarrhea, relieving constipations and bloating, managing irritable bowel syndrome. Treatment of other diseases use probiotics in combination with other therapies.
This leads us back to our question, do fermented foods contain probiotics? The short answer is some fermented foods do but not all.
Fermented foods and probiotics
With the exception of some fermented dairy foods, fermented foods by definition cannot be considered probiotics for a few reasons.
First, not all fermented foods or beverages contain live microbes in the end product. Reviewing the definition reveals that microbes must be live upon consumption. Dead microbes, microbial products, microbial components are outside the definition of probiotics (2).
Although wine and beer require yeast for fermentation, filtration physically removes yeast before bottling. Likewise, heat deactivates yeast and bacteria in sourdough bread, and chocolate and coffee bean fermentation.
Though non-essential, other fermented foods are thermally processed to extend shelf life and improve food safety. In the case of sauerkraut that sits upon grocery shelves, heat processing (canning) extends the shelf life at room temperature. Similarly, cooking fermented sausages before eating improves food safety.
Probiotics cannot broadly refer fermented foods, since some fermented foods require processes that remove or deactivate microbes before consumption.
Second, not all fermented foods and beverages contain microbes in adequate amounts for health benefits. There is variability in the number of living microbes or colony forming units (CFU) among different types of fermented foods and within the same types of fermented food.
A 2018 review showed the range of live microorganisms in fermented foods and beverages reported in published research paper. This review collected the number of CFU across 18 types of ferments (116 different food and drink sources), and highlighted the vast range of CFUs among fermented foods: <102 to 1010 CFU/gram or mL. That means the range is less than 100 colony forming units to ten billion (4).
The study also found wide variability within the same types of ferments. For example, among 4 types of sauerkrauts, the cell count for lactic acid bacteria ranged from 104 to 108 CFU/gram. That is ten thousand to 100 million cells per gram (4).
Freshness of ingredients, salt concentration, type of fermentation vessel, and age at testing may explain the variability among these sauerkraut batches. Generally, fresher ferments have higher cell counts.
The amount of microbes in the finished product is only one part in understanding why microbes in fermented foods are not probiotic. The other part is portion size.
Researchers have suggested that consumption of 1010 cells would be necessary for changes to microbes in the gut (5). In terms of fresh sauerkraut, this means 100 grams (3/4 cup). Of course, this assumes it has at least 100 million cells (108 CFU/gram).
From a nutrition standpoint, increasing portion size of salt-based fermented foods is not the best way to ensure you meet recommendation. Increasing portion size may cause you to exceed sodium levels. Doing this could affect heart health and blood pressure regulation down the road.
Instead, a better way to ensure you get 1010 cells is to consume a variety of fermented foods with live microbes. Some with sodium and some without.
Variation of cells among fermented foods and variation in portion sizes makes it hard guarantee “adequate amounts.” This is one reason why fermented foods can’t be considered probiotics.
Third, live microbes in fermented foods are only probiotics when mixtures of microbes are characterized and confirmed for health effects. This information hasn’t been determined for microbes in ferments like sauerkraut, kimchi, and pickles.
For example, research shows that finished sauerkraut contains Lactobacillus plantarum (6), but hasn’t confirmed whether it has Lactobacillus plantarum 299V, a confirmed probiotic.
This is where science lags behind what personal experience says: fermented foods with live microbes taken in adequate amounts have health benefits.
But until research defines the strains in fermented foods, we can assume microbes in fermented foods give health benefits yet are not probiotics.
Probiotic-containing products must guarantee a minimum amount of probiotics during the whole shelf-life of the product. This amount should be a dose that links with what is needed for health benefits.
In fermented foods with live microbes, many factors affect the stability of microbes during fermentation and storage, such as temperature, pH, oxygen, and spoilage microbes.
A ferment that is kept at incorrect temperatures, for example, may see a dip in microbe levels. Therefore, fermented foods can’t always provide a guaranteed level of stability, which is needed for therapeutic results.
Benefits of fermented foods regardless of probiotics
Although microbes in fermented foods are not probiotics, there are still health benefits documented from clinical and population-based studies. These should convince us of the inherent benefit of fermented foods – probiotics or no probiotics.
Kimchi, for instance, improves fasting blood glucose and other metabolic syndrome symptoms in overweight and obese adults (7). In addition, other studies report a correlation between Korean adults who consume kimchi (and other fermented foods) and fewer cases of asthma and eczema (8,9).
A new concept presented in a 2018 research paper could explain these probiotic-like with identifying a strain-specific probiotic. It suggests that there are “shared core benefits” of microbes that are from the same species or grouping (genera) (10). That means Lactobacillus plantarum microbes may share similar probiotic action as Lactobacillus plantarum 299V. Much more research is needed in this area.
Whatever the reason, we know microbes in fermented foods are still good for health because they:
- Displace and out-complete bad microbes for nutrients
- Produce short-chain fatty acids
- Make anti-microbial agents, such as bacteriocins
- Stimulate the immune system
- Enhance the gut barrier lining
- Stimulate growth of other good microbes
- Create new nutrients, specifically B vitamins
- Stabilize phytochemicals (e.g. Betalins in beet kvass) and micronutrients (e.g. Vitamin C)
- Increase extraction of polyphenols (i.e. From grape skins in red wine)
- Activate bioactive compounds (prevents disease), and
- Remove toxic compounds from fermented foods (e.g. Cyanide in cassava).
Fermented foods with probiotics
While microbes in most fermented foods, by definition, are not probiotics, fortified yogurt and some fermented dairy drinks are exceptions.
Dairy fermentation such as yogurt requires Lactobacillus bulgaricus and Streptococcus thermophilus. However, Health Canada doesn’t recognize neither of these species as probiotics. Nevertheless, these microbes digest lactose, which makes yogurt suitable for people with lactose intolerance.
Probiotic yogurt products have added probiotic strains for characteristic flavour and functional health effects beyond what is essential.
Probiotic labelling guidelines
According to Health Canada’s guidelines for probiotic labelling, probiotic foods must contain strains with confirmed health-promoting properties. There must be at least 1 billion live cells (109 CFU) per suggested serving guaranteed throughout its shelf life (11).
Still, a University of Toronto study published in 2017 revealed that probiotic yogurt products available in Canada had levels well below those used and documented in clinical trials for produce health effects (12). This suggests that not all yogurt in Canada with probiotic labelling actually contain probiotics in adequate amounts for health effects, despite labelling guidelines by Health Canada.
Probiotic yogurt in Canada
Some brands of yogurt and kefir (a fermented dairy drink) with probiotics strains, claim to have more than 1 billion live cells are listed below. Let’s hope the 2017 study has motivated yogurt brands to set better monitoring for probiotic doses through to its expiry date.
- Yogurt: Activia, plain (10 Billion Bifidobacterium lactis CNCM I-2494 and active bacterial cultures)
- Kefir yogurt: Astro Kefir Probiotic Yogurt (2 Billion Lactobacillus acidophilus NCFM, Bifidobacterium lactis Bi-07)
- Lactose-free yogurt: iÖGO Probio Immuni-T (1 Billion BB-12® Bidobacterium Lactis)
- Kefir: LIBERTÉ 1% Plain Kefir (2 Billion Lactobacillus acidophilus NCFM, Bifidobacterium lactis Bi-07)
- Greek yogurt: Organic Meadow (1 Billion+ Lactobacillus delbrueckii subsp. bulgaricus, Streptococcus thermophilus)
Not referring to microbes in fermented foods as probiotics is to communicate truthfully with people and set them up for success. For example, eating a few sticks of lacto-fermented carrot sticks will not quench digestive discomfort in the college student with IBS or treat antibiotic-associated diarrhea in an elderly man at the hospital. A structure fermented foods plan may address these; however, issues like these often require specific probiotic supplementation in adequate doses.
The bottom line is everyone (I mean everyone) should be consuming fermented foods with live microbes daily. Even people with histamine intolerance and people who are averse to the sour, tartness of lacto-fermented foods can find a suitable ferment.
Ideally, each meal should have a splash of a fermented beverages, a sip of a gut shot, a dollop of a fermented condiment, or a small side of kimchi – whatever you best tolerate. This should be the norm, even for young children.
If you want to ensure a targeted health effects, talk to you doctor, pharmacist, or dietitian to determine whether a probiotic supplement is right for you.
Finally, remember that fermented foods are more than just good microbes. Traditionally, fermentation ensured families had food from harvest to harvest. Additionally, fermentation enhanced food safety, since acidity, salt concentration, and anaerobic environments limit many harmful bacteria. But, most importantly, fermented foods improve flavour, and, really that is what eating comes down to. We eat food that tastes good and makes us feel good!