Review
Probiotics and health: new facts and ideas

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Abstract

Many trials on probiotics are now published that use established methods to demonstrate their clinical efficacy. Convincing progress has been made in the field of inflammatory bowel disease and allergy prevention in infants. Experimental studies show clear differences (and even sometimes opposite effects) between apparently closely related probiotics and suggest new mechanisms for the observed effects, such as immunostimulation by bacterial DNA and interaction with Toll-like receptors and dendritic cells in the gastrointestinal tract.

Introduction

Probiotics have been defined as non-pathogenic micro-organisms that, when ingested, exert a positive influence on host health or physiology [1]. Many physicians have long been sceptical about their efficacy, as evidence for their efficacy was low and information on the stability of the strains in the products and their survival in the gastrointestinal tract was often lacking. However, a pharmacological approach has now been used to assess the effects and pharmacokinetics [2], and both scientists and health providers are showing renewed interest. Before 1990, 22 articles on probiotics were quoted in the Medline library, whereas more than 1000 have been published in the past ten years, including more than 200 in the first six months of this year. We now know that the pharmacokinetics of probiotics varies between strains and that many are indeed effective, as shown by positive double-blind randomized controlled trials (RCTs). Probably the most interesting and unexpected data were produced in the past few years in the field of immunomodulation with probiotics: treatment of allergic diseases or inflammatory bowel diseases. We summarize here recent data and ideas.

Section snippets

Probiotics and immunomodulation

The microorganisms present in the gastrointestinal tract, including the endogenous flora, interact with the mucosal cells including epithelial cells [3••] and immune cells. Progress has been made in our understanding of the mechanism of this interaction. Considerable interest has focused on dendritic cells. Dendritic cells belong to the group of antigen-presenting cells that initiate the local immune response in the intestinal mucosa and play a pivotal immunoregulatory role in the balance of T

Probiotics and intestinal inflammation

Bacteria in the gastrointestinal tract strongly influence intestinal inflammation and the majority of inflammatory bowel diseases, both in humans and animals, are more severe in the presence of the endogenous flora. Animal studies have demonstrated that some probiotics may significantly prevent or help cure inflammatory bowel diseases. Several RCTs have now confirmed a beneficial effect in humans with pouchitis, ulcerative colitis or Crohn's disease. Gionchetti et al. [8••] performed a

Probiotics and allergy

Population-based studies suggest that increased exposure to bacteria in early life can be protective against allergy. Isolauri and coworkers 15., 16••. hypothesized that probiotics might be useful to treat or prevent allergy in infants and tested this hypothesis in two RCTs. In the first trial, 27 breast-fed infants suffering from atopic eczema were randomized to be weaned either with probiotic-supplemented extensively hydrolysed whey formula or with the same formula without probiotic [15]. The

Probiotics and intestinal microbes

Many researchers and clinicians are interested in trying to prevent or cure intestinal infections with probiotics, especially those caused by Clostridium difficile or Escherichia coli O157-H7 (see [2] and references therein). Colonization of the gastric mucosa by Helicobacter pylori is the main cause of gastritis and ulcers, and is strongly associated with gastric lymphoma and cancer. Some probiotics exert antagonistic properties against H. pylori in vitro [21]. Recent RCTs have assessed the

Probiotics to deliver active ingredients to specific targets in the gastrointestinal tract

Probiotics can be considered as an original way to deliver active constituents to targets in the gastrointestinal tract. Natural or genetically modified probiotics are a source of these constituents and also act as a vector that can protect the activities from acid in the stomach and deliver them at the site in the intestine where they should be active. It was established that yoghurt bacteria, which are easily destroyed by bile in the duodenum, deliver their intracellular lactase activity in

Conclusions

There is now real evidence that probiotics significantly influence health; however, they are not a panacea. Negative trials have also been published and should be encouraged, as one might learn from them and because no information should be hidden. New molecular tools, especially DNA microarray techniques, will allow us to further our understanding of how commensal or exogenous microorganisms modulate the expression of genes involved in several important intestinal functions including immunity.

References and recommended reading

Papers of particular interest, published within the annual period of review,have been highlighted as:

  • • of special interest

  • •• of outstanding interest

References (30)

  • P.H. Pouwels et al.

    Lactobacilli as vehicles for targeting antigens to mucosal tissues by surface exposition of foreign antigens

    Methods Enzymol

    (2001)
  • C. Dunne et al.

    Probiotics: from myth to reality. Demonstration of functionality in animal models of disease and in human clinical trials

    Antonie Van Leeuwenhoek

    (1999)
  • P.R. Marteau et al.

    Protection from gastrointestinal diseases with the use of probiotics

    Am J Clin Nutr

    (2001)
  • L.V. Hooper et al.

    Molecular analysis of commensal host-microbial relationships in the intestine

    Science

    (2001)
  • H.R. Christensen et al.

    Lactobacilli differentially modulate expression of cytokines and maturation surface markers in murine dendritic cells

    J Immunol

    (2002)

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