Foods with probiotics

Which foods contain probiotics?

This question has two layers. The first is which foods contain live microorganisms. The second is whether these microorganisms meet the definition of a probiotic. The 2021 ISAPP fermented foods consensus defines fermented foods as “foods and beverages made through desired microbial growth and enzymatic conversions of food components” and clearly distinguishes between fermented food and probiotic. ^[1]

Which fermented foods contain live microorganisms?

The table below applies the ISAPP consensus classification by presence of live microorganisms (Box 1) to foods common in Türkiye. Foods not named in the ISAPP list are marked separately.

“Present” in the table (classification: ISAPP consensus ^[1]) says that the food contains live microorganisms; it does not guarantee a specific number or a health benefit. ISAPP states that the phrase “live and active cultures” can be used only if no process that would kill or remove the fermentation microorganisms has been applied and the microorganisms are at the levels expected for that type of food; for foods pasteurized after fermentation, the phrase “made with fermentation” is considered appropriate. ^[1]

How many live microorganisms are in yogurt and kefir?

The Codex fermented milk standard (CXS 243-2003) requires starter microorganisms to be viable, active and abundant in the product until the expiry date under the storage conditions stated on the product. In the table, the total of starter microorganisms is given as at least 10⁷ CFU/g for yogurt and kefir; for kefir, yeast is additionally given as at least 10⁴ CFU/g. The live microorganism requirement does not apply to products heat treated after fermentation. ^[2] According to the standard, yogurt starter is the symbiotic culture of Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus. ^[2]

The ISAPP consensus states that a single serving of many fermented foods containing live and active microorganisms, such as yogurt or kefir, can contain up to 10¹¹ lactic acid bacteria; these microorganisms are not expected to colonize the gut for long, but some are metabolically active in the gut. ^[1]

Which microorganisms are found in kefir in Türkiye?

Kefir is not a single defined strain. In a study examining the bacterial composition of kefir grains and kefir beverages collected from different regions of Türkiye with culture-independent and culture-dependent methods (Kesmen et al.), a total of 10 bacterial species were detected with the culture-independent method. In the grains the most dominant species was Lactobacillus kefiranofaciens, while in the beverages Lactococcus lactis stood out. With the culture-dependent method, the most frequently isolated species were L. lactis, Leuconostoc mesenteroides and Lactobacillus kefiri; only three species (L. lactis, L. acidophilus, S. thermophilus) were detected with both methods. The authors state that kefir products have a microflora related to production and region. ^[3] This study shows the microbiological diversity of kefirs in Türkiye; it does not show that a kefir provides a particular health benefit.

What is the difference between a fermented food and a probiotic?

For a food to be said to “contain a probiotic,” ISAPP requires that the strain be identified below species level (at the strain level), that its genome sequence be known and that the strain be present in adequate numbers throughout the product’s shelf life; the benefit must be shown by a well-controlled human intervention trial together with evidence of safety. Traditional, spontaneously fermented sauerkrauts most likely contain more than one Lactiplantibacillus plantarum strain; these strains are not considered probiotic because they are not identified and their doses are unknown. In contrast, if a clinically proven strain (for example L. plantarum 299v) is present at an effective dose and until the end of the product’s shelf life, this sauerkraut would meet the minimum criteria for a “probiotic fermented food.” ^[1] The 2014 consensus of Hill and colleagues also defines a probiotic as “live microorganisms that, when administered in adequate amounts, confer a health benefit on the host.” ^[4]

According to ISAPP, the majority of fermented foods sold commercially today are not expected to fall into the “probiotic fermented food” category. One example at the regulatory level: ISAPP reports that the European Food Safety Authority (EFSA) approved a health claim that live yogurt cultures improve lactose digestion; this claim rests on the lactase enzyme contained in the yogurt cultures (L. delbrueckii subsp. bulgaricus and S. thermophilus). ^[1]

What do “live and active cultures,” “made with fermentation” and “probiotic” mean on a label?

ISAPP distinguishes three separate kinds of label wording. For fermented foods containing live microorganisms, the phrase “contains live and active cultures” is appropriate; for foods without live microorganisms (for example, those pasteurized after fermentation), the phrase “made with fermentation” can be used. The word “probiotic” is considered appropriate only together with a supported health benefit claim and when there is strain-level evidence. The terms fermented food and probiotic cannot be used interchangeably. ^[1] The same text also reports that Health Canada recognizes more than 20 Lactobacillus genus complex and Bifidobacterium species as “probiotic” in foods, provided at least 10⁹ CFU per serving is delivered; even in this case, ISAPP emphasizes the conditions of strain identification, genome sequence and adequate numbers throughout shelf life. ^[1]

What risks are there in fermented foods?

Some components of fermented foods can pose a safety risk under certain conditions. According to the ISAPP consensus, alcohol and salt (for example in soy sauce or kimchi) are natural components of some fermented foods and should be consumed in moderation. During the fermentation of cheese, meat, vegetables, soybeans and wine, some lactic acid bacteria form biogenic amines such as histamine and tyramine from amino acids; when the host’s detoxification systems are insufficient, these can cause effects ranging from mild to severe, such as migraine. Hygiene and appropriate starter culture selection are listed among the methods used to reduce this formation. ^[1]

Is the health effect of fermented foods proven?

The evidence differs by food. According to the ISAPP consensus, more than twenty RCTs have been conducted with yogurt and fermented dairy products; milk kefir, kimchi, sauerkraut, natto, vinegar and sourdough bread have been examined in at least one RCT. For other fermented foods such as kombucha, evidence of health benefit rests mostly on chemical analyses and animal and cell culture models. ISAPP also states that most of the evidence on the association of yogurt and fermented dairy products with health rests on prospective or epidemiological studies. ^[1]

This guide does not give personal nutrition or product recommendations; for people with suppressed immunity or severe illness, the suitability of products containing live cultures is evaluated with a physician.