Explore the growth response of bifidobacteria.

Dairy foods that contain probiotic bacteria are common outside the United States. But an increasing number of U.S. cultured dairy food makers have started to add probiotics to their products to offer augmented health benefits. In order to do this, researchers have to identify and characterize probiotic cultures, then confirm their viability through a dairy product's shelf life and digestion. Milk may be the preferred vehicle for supplementing the body with these beneficial bacteria.

Scientists are investigating the growth responsiveness of bifidobacteria in the presence of various dairy components, including lactoferrin. Initial research involved assessing the effect of bovine and human iron-saturated lactoferrin, and iron-free and bovine recombinant lactoferrin, on enhancing viable cell counts of Lactobacillus and Bifidobacterium and reducing counts of potentially toxin-producing bacteria in vitro. Results from the in-vitro studies were positive.

By using an in-vivo mouse model, investigators next want to confirm the ability of lactoferrin to enhance the growth of bifidobacteria directly through viable cell counts or indirectly by reducing toxin-producing intestinal bacteria and endotoxin concentrations in stool filtrates.

In addition, scientists will determine mucosal immunologic stimulation by bifidobacteria and lactoferrin in the mouse gut by monitoring certain cytokine inflammatory responses and the stimulation of precursor B and T cell subsets.

A variety of health benefits have been linked to the consumption of probiotic bacteria with varying levels of supporting evidence. Only a few of these benefits have been confirmed by the scientific community. Improving lactose digestion in lactase-deficient individuals and alleviating certain types of diarrhea are two well-documented benefits.

The mechanisms by which probiotics affect the microecology of the gastrointestinal tract are speculative, although several mechanisms of action have been observed. Antibacterial agents, including organic acids and bacteriocins, are produced and excreted by probiotic bacteria. They may have an inhibitory effect on undesirable and pathogenic microflora in the gastrointestinal gut.

Human breast milk, which contains bioactive components that encourage the growth of intestinal bifidobacteria in infants, may alter bacterial antagonism for essential nutrients and impede overgrowth of undesirable aerobes. Modulation of the immune response may suppress potential pathogens and carcinogens.

Specific competition for adhesion receptors to gut epithelium may allow Lactobacillus and Bifidobacterium to occupy the niche normally required by toxin-producing organisms for colonization. Probiotic bacteria supply lactase to the small intestine, thereby facilitating lactose digestion and preventing its use by bacteria in the colon. Further information. Linda Duffy, Executive Director, Women and Children's Health Research Foundation, Children's Hospital of Buffalo, 888 Delaware Ave., Buffalo, NY 14209; phone: [phone]; fax: [phone].