Evidence suggest that colonic bacteria are able to modulate immunity. Probiotic supplements have been shown to produce immune benefits, and modification to immune parameters has been reported. Changes following supplementation include increases in natural killer cells, lymphocytes and immunoglobulin A. These changes are associated with decreases in the severity, duration and frequency of gastrointestinal and upper respiratory tract infections. For example, Lactobacillus casei supplements have shown beneficial effects against infection in clinical studies. However, their benefits to stressed populations is still unclear as studies involving military personnel and athletes have been inconsistent. One positive study investigated the effects of Lactobacillus casei supplements on the incidence of respiratory infection and gastrointestinal infection in healthy shift workers. The study was a randomised, double blind study involving 1000 subjects who received 200g/d of Lactobacillus casei supplement or a placebo for 3 months.
The odds ratio for common infectious diseases when comparing individuals in the treatment group with the control group was 0.75, suggesting improved immunity with Lactobacillus casei supplements. The treatment group also contained a reduced number of subjects experiencing 1 infectious episode compared to the control group. Lactobacillus casei supplementation also increased the time to the first reported infectious episode significantly. Smokers benefited from Lactobacillus casei supplementation, with a reduced number of cumulative infections. Infected subjects in the treatment group displayed milder symptoms during their illness, as assessed by reduced fever duration, and increased natural killer cell and leukocyte counts and activity. The authors reported that the Lactobacillus casei supplements were well tolerated, which suggests that probiotics may be a safe and effective treatment for common infectious diseases when given as dietary supplements. Those with low colonic cell counts may benefit the most.
RdB
