World Digestive Health Day WDHD – May 29, 2016 PROBIOTICS AND PREBIOTICS FOR GUT HEALTH: THE ESSENTIALS, continued human epithelial cells; possess antimicrobial activity against potentially pathogenic bacteria; reduce pathogen surface adhesion; possess bile salt hydrolase activity; and be resistant to spermicides. Depending on the final applications and entry routes of hosts, most industries will first pre-screen putative probiotic strains for these properties prior to health and nutraceutical assessments. DOSING AND TIMING OF PROBIOTICS The optimal effective dose at which probiotics produce clinical benefit remains unclear. Present clinical studies have utilized a minimum daily therapeutic dose of 106 to 109 colony forming units (CFU).3 The duration of probiotic therapy also varies among hosts and targeted therapeutic effects, and thus it is advisable for probiotics to be taken continuously. Although host and physiology dependent, Saccharomyces boulardii has been reported to be cleared from the body within three to five days after stopping as compared to Enterococcus faecium, which reportedly persisted for five weeks after probiotic intake in humans. A meta-analysis by Ritchie et al. reported that some probiotic strains showed significant clinical efficacy when taken for as little as one week up to 240 weeks.4 Hunger et al. suggested that probiotics should be taken for at least one month in those with lower gastrointestinal (GI) symptoms5 and a longer period is needed for metabolic diseases. Various factors affect such dosing variations; a) the original gut microbiota profile of hosts, as probiotics need to colonize to exert certain health benefits and should the original gut microorganisms prevent such colonization, thus the effects of probiotics are hindered; b) the diet and physiology of hosts such as fibers and polysaccharide intake which alter the unstirred layer of the intestinal epithelium will change the attachment of probiotics to gut lining; c) gut-related diseases which increase the concentration of toxic metabolites to probiotics will hinder their survival; d) metabolism of hosts often vary, leading to different dosage and time needed for a beneficial effect to be materialized; e) unlike drugs, most mechanisms and specific targeted sites of health benefits by probiotics remain unknown, thus variation will remain. No definite recommendation on proper timing of probiotic consumption has been made so far. Certain strains, such as Lactobacillus rhamnosus and Saccharomyces boulardii, may be administered before a meal or just after a fat-containing meal to avoid resistance to gastric acid but many commercial strains nowadays have been tested for acid resistance before production. Tripathi et al reviewed the literatures on acid and bile tolerance of several Bifidobacteria species and noted that Bifidobacterium longum survived best.6 Some Lactobacillus species are able to survive in environments between pH 3.7 up to 6.0. Presently, commercial products have addressed this issue by providing more effective delivery systems via microencapsulation, enhanced coatings, and drying methods to enhance strain viability. Consumption would clearly depend on individual probiotic strain properties, as well as, product formulation. SAFETY OF PROBIOTICS The US Food and Drug Administration (FDA) defined probiotics as Generally Recognized as Safe (GRAS).7 However, there are many commercial probiotic preparations available with different species, strains, and efficacy. Therefore, safety assessments are strain-specific and the GRAS status does not cover all probiotic products per se. The European Union (EU) project on biosafety evaluation of probiotics (PROSAFE) recommends the following safety measures: proper identification of microbial strain via biochemical and molecular methods; determination of antibiotic resistance and transfer; standard antimicrobial susceptibility testing; in vitro assessment of virulence; and in vivo assessment of strain pathogenicity.8 The Agency of Healthcare Research and Quality (AHRQ) together with the National Institutes of Health (NIH) have reviewed in detail the existing literatures on safety of probiotics. 7 Amid rare systematic reporting of adverse events, the authors concluded that present randomized controlled trials (RCTs) did not show an increased risk of adverse events for children, adults, or elderly.7 In this regard, probiotics can be theoretically consumed in people of all ages. Common side effects include abdominal cramps, nausea, flatulence, and taste disturbances, which are usually observed only in the first three days of consumption and may not be attributed to the probiotics. Excipient materials used for production and the addition of prebiotics to probiotics can impart GI side effects due to their indigestible nature. Although rare, certain probiotic strains could produce more acids than others, leading to increased gut motility and subsequently exerting gut discomfort. This is normally not detrimental to health and may actually be useful in combating pathogenic bacteria in the gut. The most important concern regarding probiotic use is the risk of sepsis. Probiotic bacteria, such as Lactobacillus casei and Lactobacillus rhamnosus, have been observed to cause World Digestive Health Day WDHD May 29, 2016 WGO Handbook on DIET AND THE GUT 47
WGO Handbook on Diet and the Gut_2016_Final
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