Abstract
Thirty healthy, male subjects (age 18 to 75 yrs) were used in a two-group, double-blinded, parallel design to evaluate the safety and tolerance of a potential probiotic organism, Lactobacillus reuteri. Subjects (15/treatment) consumed two gelatin capsules daily for 21 d that contained either a freeze dried L. reuteri preparation in a cryoprotectant, or a placebo (cryoprotectant). The concentration of L. reuteri was such that subjects consumed 1 × 1011 CFU per day. The study was 28 d in length with daily documentation of the presence of gastrointestinal symptoms (nausea, diarrhoea, cramping, distention, flatulence, vomiting, constipation, burping and reflux). In addition, serum chemistries, haematology, urinalysis, urinary indican excretion, and faecal microbiota (L. reuteri and total Lactobacillus spp. enumeration) were measured weekly (day 0, 7, 14, 21 and 28). A physical exam was given on day 0, 21, and 28. An additional faecal sample was obtained on day 77 for microbial enumeration. Subjects could consume their regular diets; however, alcohol was not allowed. Physical exam and urinalysis parameters were not clinically different between treatments. Supplemental L. reuteri reduced (P < 0.05) urinary indican excretion at day 7, but had no effect (P > 0.05) on subsequent urine collections. Although significant differences were observed for a few of the serum chemistry and haematology variables, all of the values remained within the expected normal range for healthy adult males. Subjects consuming supplemental L. reuteri had increased (P < 0.01) levels of L. reuteri in their faeces on day 7, 14, 21, and 28. However, colonisation was lost within 2 mths of termination of L. reuteri consumption (day 77). Levels of total Lactobacillus spp. never differed (P > 0.05) between treatments; however, the ratio of L. reuteri: total Lactobacillus spp. increased (P < 0.05) for subjects consuming supplemental L. reuteri. Incidence of subjective tolerance factors was infrequent and similar for both treatments. In conclusion, supplemental L. reuteri may be fed at 1 × 1011 CFU/day without any clinically significant safety or tolerance problems. Intake of L. reuteri (1 × 1011 CFU/day) results in colonisation (as measured by faecal level) within 7 d of consumption and is maintained for at least 7 d post consumption; however, colonisation is lost within 2 mths of washout.