Independent and Interactive Effects of Habitually Ingesting Fermented Milk Products Containing Lactobacillus casei Strain Shirota and of Engaging in Moderate Habitual Daily Physical Activity on the Intestinal Health of Older People

Abstract

Infrequent bowel movements decrease the number of beneficial bacteria in the human intestines, thereby potentially increasing the individual's risk of colorectal cancer. The correction of such bowel problems could therefore make an important contribution to improving population health and quality-adjusted lifespan. We examined independent and interactive effects upon the fecal microbiota of two potentially favorable determinants of intestinal motility: the intake frequency of a fermented milk product containing Lactobacillus casei strain Shirota (LcS) and the quantity/quality of habitual physical activity in 338 community-living Japanese aged 65-92 years. Subjects were arbitrarily grouped on the basis of questionnaire estimates of LcS intake (0-2, 3-5, and 6-7 days/week) and pedometer/accelerometer-determined patterns of physical activity [<7000 and ≥7000 steps/day, or <15 and ≥15 min/day of activity at an intensity >3 metabolic equivalents (METs)]. After adjustment for potential confounders, the respective numbers of various beneficial fecal bacteria tended to be larger in more frequent consumers of LcS-containing products, this trend being statistically significant (mostly P < 0.001) for total Lactobacillus, the Lactobacillus casei subgroup, and the Atopobium cluster; in contrast, there were no statistically significant differences in fecal bacterial counts between the physical activity groups. A multivariate-adjusted logistic regression analysis estimated that the risk of infrequent bowel movements (arbitrarily defined as defecating ≤3 days/week) was significantly lower (P < 0.05) in subjects who ingested LcS-containing products 6-7 rather than 0-2 days/week [odds ratio (95% confidence interval) 0.382 (0.149-0.974)] and was also lower in those who took ≥7000 rather than <7000 steps/day [0.441 (0.201-0.971)] or spent ≥15 rather than <15 min/day of physical activity at an intensity >3 METs [0.412 (0.183-0.929)]. The risk of infrequent bowel movements in subjects who combined 6-7 days/week of LcS with ≥7000 steps/day or ≥15 min/day of activity at >3 METs was only a tenth of that for individuals who combined 0-2 days/week of LcS with <7000 steps/day or <15 min/day at >3 METs. These results suggest that elderly individuals can usefully ingest LcS-containing supplements regularly (≥6 days/week) and also engage in moderate habitual physical activity (≥7000 steps/day and/or ≥15 min/day at >3 METs) in order to enhance their gastrointestinal health.

Keywords: aging; constipation; defecation; exercise intensity; gut microbiota; intestinal motility; probiotics; step count.

FIGURE 1

Numbers of fecal microbiota in subjects consuming fermented milk products containing Lactobacillus casei strain Shirota (LcS) 0–2, 3–5, or 6–7 days per week. Values are means ± standard deviations. Linear trends for three-group differences in each bacterial count were assessed by analyses of covariance, after adjusting data for age, sex, body mass index, smoking status, and alcohol intake; if the trends were statistically significant, post hoc Tukey’s tests assessed two-group differences in each bacterial count. ^††P < 0.01 and ^†††P < 0.001, respectively, versus 0–2 days/week; ^‡‡‡P < 0.001 versus 3–5 days/week. Data on overall fermented milk products are not shown, mainly because of their similarities to those on LcS-containing products.

FIGURE 2

Numbers of fecal microbiota in subjects taking exercise demanding an energy expenditure >3 metabolic equivalents (METs) for <15 or ≥15 min per day. Values are means ± standard deviations. Independent differences in each bacterial count between groups were assessed by analyses of covariance, after adjusting data for age, sex, body mass index, smoking status, and alcohol intake. Data on step count are not shown, mainly because of their similarities to those on the duration of exercise >3 METs.

FIGURE 3

Relative abundances of the fecal bacteria families (limited to a share ≥0.1%) in subjects consuming fermented milk products containing Lactobacillus casei strain Shirota (LcS) 0–2, 3–5, or 6–7 days per week. Values are means ± standard deviations. Linear trends for three-group differences in each bacterial abundance were assessed by analyses of covariance, after adjusting data for age, sex, body mass index, smoking status, and alcohol intake; if the trends were statistically significant, post hoc Tukey’s tests assessed two-group differences in each bacterial abundance. ^†P < 0.05 versus 0–2 days/week. Data on overall fermented milk products are not shown, mainly because of their similarities to those on LcS-containing products.

FIGURE 4

Relative abundances of the fecal bacteria families (limited to a share ≥0.1%) in subjects taking exercise demanding an energy expenditure >3 metabolic equivalents (METs) for <15 or ≥15 min per day. Values are means ± standard deviations. Independent differences in each bacterial abundance between groups were assessed by analyses of covariance, after adjusting data for age, sex, body mass index, smoking status, and alcohol intake. ^*P < 0.05 versus <15 min/day at >3 METs. Data on step count are not shown, mainly because of their similarities to those on the duration of exercise >3 METs.