There are thousands of studies on thousands of different probiotic strains. Here, we focus on studies that review the efficacy of Bifidobacterium lactis Bl-04 and Lactobacillus acidophilus NCFM.

It has been well established that antibiotics can induce diarrhea and digestive disturbances. A 2009 clinical study gave 40 volunteers a probiotic mixture or a placebo and studied their digestive health during and after antibiotic use. The test revealed that post-antibiotic fecal microbiota in probiotic-consuming subjects were more similar to the baseline microbiota than the control group. This study concludes the probiotics bolster a more rapid return to pre-antibiotic baseline fecal bacterial microbiota. Simply put, probiotics helped people return to normal digestive health after taking antibiotics.

A more recent study was performed on a larger test group of 503 subjects. Patients on antibiotics were given probiotics or a placebo and studied up until 7 days after final antibiotic usage. Between the three groups, 12.5% - 19.6% of probiotic patients experienced antibiotic-associated diarrhea (AAD), while 24.6% of the placebo group struggled with AAD. Another digestive issue, C. difficile-associated disease (CDAD), which is often triggered by antibiotics, was less prevalent in the group taking probiotics. Patients taking probiotics also experienced lower incidence of liquid stools, fever, abdominal pain and bloating.

A pilot study in 2008 examined the effect of seven different probiotic strains on the immune system of 83 healthy adults. They studied immune markers in their subjects and found that the placebo and treatment groups showed similar IgA concentrations However, IgG levels were increased in the subjects taking Bifidobacterium lactis Bl-04 and Lactobacillus acidophilus La-14. Six of the seven strains also showed improvements in immunoglobulin serum concentrations compared with controls.

A randomized, double-blind, placebo-controlled study found consumers taking Bifidobacterium lactis Bl-04 had experienced lower risk of upper respiratory infection than a placebo group. Another probiotic blend in the study did not show results comparable to Bifidobacterium lactis Bl-04.