A nine week study with 29 healthy adult women analyzed the effects of cultured yogurt on bowel movements and microflora. The subjects were divided into two groups: one consumed a yogurt fortified with the probiotic BB-12; the other consumed a placebo yogurt. Days of bowl mobility increased during the period of BB-12 administration, as did the frequency of completing bowel movements. Subjects with fewer bowel movements also observed a positive change in bowel shape during intake of BB-12. Overall improvements in microbiota including a decrease in Bacteroidaceae and increase in Bifidobacterium in all yogurt treated subjects compared to placebo were noted, as well as an increase in Lactobacillus. (1)

In another 8 week study, 41 healthy women subjects were randomly divided into two groups. One group ingested a test food inoculated with various probiotic strains including Bifidobacterium lactis (BB-12), the other group a culture mixture placebo which did not contain b.lactis. The two groups were further characterized as having fewer bowel movements and normal bowel movements. Increases in bowel movement frequency, amount of produced bowels proportion of Bifidobacterium count to total bacterial count, and improvements in color and odor were shown after ingestion of the cultured test food. Bowel form and comfort after completing a bowel movement similarly showed significant improvement after ingestion of the BB-12 test food. The fewer bowel movement sub-group exhibited significant improvement in bowel movement frequency and a lessening of bowel odor when the test food was ingested. (2)

The safety and efficacy of a probiotic yogurt supplemented with B.lactis BB-12 on intestinal functions was studied on healthy male and female volunteers over a 7 week period. 36 subjects were divided into two groups of 18, with a subgroup divided into fewer bowel movements versus normal bowel movements. For the participants with lower bowel movements intake of the probiotic yogurt led to a substantially increased improvement in bowel movements. For both the placebo and probiotic yogurt, no effect on quantity or form of bowels was observed. Bowel movement comfortability also improved significantly in subjects with fewer bowel movements. Stool analysis from the group with the BB-12 yogurt intake, showed a significant increase in Bifidobacterium species, as well as an increased Bifidobacterium ratio of flora in the gut. (3)

A 7 month study of 209 elderly patients in nursing homes evaluated the normalization of bowel movements following supplementation. Subjects were randomly divided into three groups: Group 1 received a fermented oat beverage containing B. longum, Group 2 received a fermented oat beverage containing B. lactis BB-12 and Group 3 received a pasteurized fermented oat drink without bacteria (placebo). All subjects were assessed at baseline and at 6 months, with study products being administered and bowel movements recorded daily. Subjects receiving the B.lactis BB-12 drink showed a significant change in normalizing bowel movements compared to placebo with 30.5% of subjects having normal bowel movement at least 30% of the days, compared to 13.7% in the placebo group. The subjects receiving B. lactis BB-12 reported a higher frequency of bowel movements when also compared to placebo. (1)

A study of over 1000 healthy adult subjects evaluated the effect of Bifidobacterium animalis subsp. lactis, BB-12 on two primary endpoints: bowel movement frequency and gastrointestinal well-being. Subjects were randomised to two dosages of BB-12 or a placebo capsule once daily for 4 weeks. Bowel habits, relief of abdominal discomfort, symptoms and overall GI well-being were evaluated. Bowel movement frequency was significantly higher in the BB-12 treatment group compared with placebo at all weeks. Abdominal pain and bloating decreased during the study in both treatment groups. The consistency of produced bowels became softer in all the treatment groups, showing an overall treatment effect by the end of week four. (2)

After screening 1090 men and women by applying the 13C-urea breath test, 237 otherwise healthy subjects (22%) were identified as Helicobacter pylori-positive. A subgroup of 88 volunteers, 43 men and 45 women, were enrolled in the study after a complete physical and laboratory examination. For eight weeks participants were given either Lactobacillus acidophilus LA-5 plus Bifidobacterium lactis BB-12 or placebo. The number of days with watery stools was 60% lower in the probiotic treatment group. Frequency, duration and severity of abdominal pain, flatulence, passing of gas, nausea and passage of mucus with stool, which were observed during or already before antibiotic treatment, were significantly reduced in the LA-5 plus BB-12 group as well. (1)

A study of 396 subjects evaluated the severity of Antibiotic Associated Diarrhea (AAD) in those who were slated for a 7-day round of antibiotics. Participants were randomized into either the probiotic group containing Lactobacillus acidophilus LA-5 and Bifidobacterium lactis BB-12 (4 Billion CFU) or placebo. A total of 176 (89%) in the probiotic group and 167 (84%) in the placebo arm completed the study in which a 14-day therapy (concomitant with antibiotic course and seven days thereafter) of the probiotic formulation in preventing AAD was evaluated. The analysis of the duration and severity of diarrhea in subjects who had AAD reveals that the median duration of diarrhea in the probiotic group was 2 days with an interquartile (IQR) range of 1-3 days compared to 4 days (IQR of 3 to 5.5) in the placebo group. This difference was statistically significant. Subgroup analysis of subjects with AAD shows that the incidence of severe diarrhea was 96% in the placebo group (25 out of 26) compared to 31.6% (6 out of 19) in the probiotic group and this difference was also significant statistically. (2)

Approximately 70-80% of immune cells are associated with the gut mucosa. This allows probiotics the ability to communicate with and affect the immune system.

The mechanism of action in which probiotics support the immune system is hypothesized through competing for nutrients by the colon, colonization site interference, and competition for binding sites on gut epithelial cells, production of bacteriocin, lowering of colonic pH, and nonspecific stimulation of the immune system.

In a 2008 randomized, double-blind and placebo-controlled parallel group intervention study, the immunomodulatory effects of healthy individuals supplemented with probiotics for 3 weeks were evaluated in vivo. Immune and inflammatory markers measured were c-reactive protein, serum cytokines, blood cells and immunoglobulins. After 3 weeks of supplementation, subjects consuming the probiotic, Lactobacillus rhamnosus GG (LGG) showed decreased C-Reactive Protein (CRP) levels (3)

Researchers conducted experiments to investigate the adhesion and anti-inflammatory properties of the probiotic strain Lactobacillus rhamnosus GG (LGG) in colonic mucosa in vivo and in an organ culture ex vivo. For the ex-vivo experiment, samples from healthy subjects were evaluated for adhesion and cytokine expression quantification with 3 doses of LGG: regular (6 x 106 CFU), double (1.2 x 107 CFU) or 5-fold (3 x 107 CFU). In vivo, subjects were given a standard dose of 1.2 x 1010 CFU for 7 days.

Outcomes of this study found that LGG effectively adheres to colonic mucosa and modulates inflammation markers, both in an experimental model and in vivo. After 7 days of consumption, LGG effectively colonized the mucosa using the standard dose, however a higher dose of LGG was associated with increased mucosal adhesion. Additionally, LGG induced a reduction in proinflammatory cytokines TNF-ɑ and IL-17 with all doses. The highest reduction was seen with the double dose. 25% reduction of TNF-ɑ and 18% reduction for IL-17 (4).

Immunoglobulins play a key role in the body's immune system. They are proteins produced by specific immune cells called plasma cells in response to bacteria, viruses, and other microorganisms as well as exposures to other substances that are recognized by the body as "non-self" harmful antigens. In the below study, immunoglobulins were used as a marker of immune system response.

Rizzardini et al studied the impact of probiotics on healthy subjects in a vaccination model. Using a randomized, double-blind, placebo controlled trial, volunteers were given capsules containing a minimum 1x109 CFU Bifidobacterium lactis BB-12 or placebo for 6 weeks. After 2 weeks of supplementation, subjects were given a seasonal influenza vaccine. Outcome of the study found that vaccine specific antibody responses (vaccine-specific IgG and subclasses IgG1 and IgG3) were significantly greater in the probiotic group than in placebo. For vaccine-specific salivary IgA, a significantly greater MFI was found in probiotic participants than placebo. Additionally, individuals in the probiotic group saw a significantly higher minimum two-fold increase in antibody levels than placebo. It can be supported that probiotic supplementation leads to an increased adaptive immune response to vaccination (5).