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Bugs in Our Guts—Not All Bacteria Are Bad
How Probiotics Keep Us Healthy

(Released September 2006)

  by Leila Kiani  


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Probiotic bacteria have a long history of association with dairy products. This is because some of the same bacteria that are associated with fermented dairy products also make their homes in different sites on the human body, including the mouth, the gastrointestinal tract and the vagina. Some of these microbes, therefore, can play a dual role in transforming milk into a diverse array of fermented dairy products (yogurt, cheese, kefir, etc.), and contributing to the important role of colonizing bacteria (6).

The consuming public may have a generally negative image of bacteria in foods, but they are aware of "live, active cultures" in fermented dairy foods, and these cultures convey a positive, healthful image. Information about probiotic bacteria can be an extension of the comfortable association of cultures in dairy products, and make it easier to communicate health messages to the public (6).

A dairy product containing probiotics makes a healthy "functional food package." In addition to the vitamins, calcium, other minerals, and protein obtained from milk products, modern research has suggested healthful properties of fermentation-derived peptides and butyric acid found in some dairy products. Dairy products have recently been shown to be important for a healthy diet, doing more than preventing osteoporosis. Consumption of three or more servings of dairy products each day has been associated with lower levels of obesity, and hence lower incidence of diabetes, hypertension and heart disease. The DASH (Dietary Approaches to Stop Hypertension) diet also recommends three servings of lowfat dairy products. Considering all these findings, dairy products combined with probiotic bacteria may translate into improved long-term health (6).

Numerous commercial products containing LAB have been associated with healthy function. Basic conditions for LAB strains to be used as probiotics have been reported to include the following: (a) general recognized as safe (GRAS) (b) able to keep their viability during processing and storage, (c) tolerant to acid and bile, (d) able to adhere to the intestinal epithelium of the hosts, and (e) antagonistic activity against bacterial pathogens (8).

Probiotics are provided in products in one of three basic ways (6):

  • as a culture concentrate added to a food (usually a dairy product) at medium levels, with little or no opportunity for culture growth
  • inoculated into a milk-based food (or dietary supplement) and allowed to grow to achieve high levels in a fermented food
  • as concentrated and dried cells packaged as dietary supplements such as powders, capsules, or tablets
Foods are the best choice for delivering probiotics due to the synergistic effect between components of foods and probiotic cultures. The natural buffering of stomach acid by food also enhances the stability of consumed probiotics. Dairy products containing probiotics provide a number of high quality nutrients, including calcium, protein, and conjugated linoleic acids. Taking supplements, although convenient, has always posed the problem of long term compliance, whereas incorporating foods containing probiotics into daily food choices can become a lifestyle habit (15).

Supplements Trade Names (5)

The dietary supplement market for probiotic cultures seems to be a more diverse and more active market than probiotics for dairy. The supplement market contains many different product formats and contents, including capsules, liquids, tablets and even food-like formats. If properly prepared and stored, probiotic bacteria can remain viable in dried form and reach the intestine alive when consumed. A diverse array of bacterial genera and species are represented in these products, including many different lactobacilli, bifidobacteria and less commonly, Enterococcus, Bacillus, Escherichia coli and yeast. Dietary supplement products are purchased primarily in health food stores or natural foods grocery stores (6).

Commercial Probiotic Strains

This table lists some commercial probiotic strains currently available. Probiotic species are listed as reported by manufacturer. This speciation may not reflect the most current taxonomy (6).

L. acidophilus NCFM®
Rhodia, Inc. (Madison, WI)
L. acidophilus SBT-2062*
B. longum SBT-2928*
Snow Brand Milk Products Co., Ltd. (Tokyo, Japan)
L. rhamnosus R0011
L. acidophilus R0052
Institut Rosell (Montreal, Canada)
L. acidophilus LA-1
L. paracasei CRL 431
B. lactis Bb-12
Chr. Hansen (Horsholm, Denmark)
L. casei Shirota*
B. breve strain Yakult*
Yakult (Tokyo, Japan)
L. casei Immunitas
Danone (Paris, France)
L. fermentum RC-14
L. rhamnosus GR-1
Urex Biotech (London, Ontario, Canada)
L. johnsonii La-1 (same as NCC533 and formerly L. acidophilus La-1)
Nestlé (Lausanne, Switzerland)
L. plantarum 299V
L. rhamnosus 271
Probi AB (Lund, Sweden)
L. reuteri SD2112
Biogaia (Raleigh, NC)
L. rhamnosus GG*
Valio Dairy (Helsinki, Finland)
L. rhamnosus LB21
Lactococcus lactis L1A
Essum AB (Umeå, Sweden)
L. salivarius UCC118
University College (Cork, Ireland)
B. longum BB5361*
Morinaga Milk Industry Co., Ltd. (Zama-City, Japan)
B. lactis HN019 (DR10)
L. rhamnosus HN001 (DR20)
Fonterra (Wellington, New Zealand)
L. acidophilus LB
Lacteol Laboratory, (Houdan, France)
L. paracasei F19
Medipharm (Des Moines, Iowa)
*strains have been awarded official functional food (FOSHU) status in Japan To have a strain added to this table, please contact with information to justify the strain's inclusion and contact information

Yogurt and milk to which probiotic bacteria have been added, such as acidophilus milk, and fermented milk products, such as kefir, are the primary food sources of probiotics in the United States. Europe and Asia lead the rest of the world in offering a variety of other food products containing probiotics. We will probably see products such as probiotic-fortified energy bars, juices, cereals and cheeses introduced into US over the next few years as well (15).

Some recent moves by U.S. food companies toward a warmer embrace of the probiotic concept are exhibited with the marketing of Lactobacillus as a dietary supplement (Culturelle) by ConA-gra (Omaha, Neb.), the entry of Dannon (Tarrytown, N.Y.) into the dairy beverage market with Actimel (labeled as a dietary supplement, containing yogurt cultures and Lactobacillus casei), and the addition by Stoneyfield Farm (Londonderry, N.H.) of four probiotics to all of its yogurt products (3).

Safety concept of microorganisms in food and feed

Europe takes a slightly different approach than the United States to issues of microorganisms and food safety. The qualified presumption of safety (QPS) approach of microorganisms in food and animal feed is a system similar in concept and purpose to the Generally Recognized as Safe (GRAS) definition used in the USA, but modified to take account of Europe's different regulatory practices. QPS provides a mechanism to recognize and give weight to prior knowledge when assessing the safety of microorganisms in food and feed production. QPS appears applicable to food, feed and microbial products from the viewpoint of safety assessment; however a number of issues need careful consideration before QPS could be introduced into the European safety evaluation (9).

diagram for QPS assessment
A general scheme for the assessment of suitability for QPS status of microorganisms

With the exception of those encompassed, in Europe, by Novel Food Regulation, microorganisms used for fermentation of food are presently not subject to community regulation. In contrast, microorganisms used as feed additives or plant protect products are comprehensively regulated. This has led to illogical situations in Europe where the same strains used freely in human foods have been the subject of stringent safety assessment when seeking community approval as a feed additive. The QPS approach represents a possible route to harmonization of approaches for the safety assessment of microorganisms used in feed/food production without introducing unnecessary measures in area where there has been no great concern about safety, while allowing more important safety concerns to be addressed. Therefore, QPS is as an operating procedure within European Food Safety Authority (EFSA) for risk assessment (9).

Many probiotic products are available. These contain various Lactobacillus strains, Bifidobacterium strains, combinations of lactobacilli and bifidobacteria and combinations of probiotics and prebiotics. Typical doses of probiotics range from one to ten billion colony-forming units (CFU). Probiotics need to be consumed at least a few times a week to maintain their effect on the intestinal microecology (5). Some strains do not lead to adverse events even if administered at a 109 - 1010 level to neonatal patients in a serious state, who appear to be the immunologically weakest of recipients, nor do these strains harm patients after highly invasive surgery on digestive organs (7). Probiotic strains can be administered to the customer in lyophilized form in sealed bags, tables or capsules, or in yogurt, other dairy products or in fruit juices. The storage time for lyophilized products is significantly longer. For each final product, the number of live cells has to be declared and the storage time at different temperature clearly stated. Today, this is the case for but a few products. Since probiotic microbes have different beneficial properties an optional product may need the combination of several strains (10).

In spite of inherent difficulties establishing good measures of probiotic efficacy, studies on lactose intolerance, diarrhea and colon cancer show that a daily dose of lactic acid bacteria is needed for any measurable effect. Unfortunately, the concentration of probiotics in food products varies tremendously and there are currently no national standards of identity for levels of bacteria required in yogurt or other fermented products. Epidemiological data on the safety of dairy products and a thorough review of the safety data suggests no evidence of probiotics being involved with human infections. However, there always remains the possibility that probiotic consumption can cause infection or other side effects and that individuals will respond in different ways to a specific strain. The food industry will need to carefully assess the safety and efficacy of all new species and strains of probiotics before incorporating them into food products (2).

✓ Contraindications

Probiotics are contraindicated in those hypersensitive to any component of a probiotic-containing product (5).

✓ Precautions

Pregnant women and nursing mothers should only use probiotic nutritional supplements if recommended by their physicians (5).

The use of probiotics for the treatment of any disorder must be medically supervised.

✓ Adverse Reactions

The most common adverse reactions to probiotics are gastrointestinal and include flatulence and constipation. Probiotics are generally well tolerated. Four cases of Saccharomyces boulardii fungemia have been reported. All of the patients had indwelling catheters, and the fungemia was thought to be due to catheter contamination (5).

There are a few reports of Lactobacillus bacteremia and endocarditis. In all cases, underlying conditions have been present, including cancer, diabetes mellitus and recent surgery (5).

In the United States, it is essential to have scientific substantiation if a statement (known as a structure/function statement) about the effect of probiotics on the normal functioning of the human body is made on a food or dietary supplement product or during promotion of the product. The burden of proof rests with the manufacturer. Although the Food and Drug Administration (FDA) does not require premarket approval of such statements, the manufacturer must provide scientific justification of any health statements if asked by the FDA (6).

Thanks to Deborah Whitman for all of her help, without which this Discovery Guide would never have been written

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