Relationships between dietary diversity and gut microbial diversity in the elderly

Diet is considered as a major driver of gut microbiota composition. However, little is known about the relationship between overall dietary balance and gut microbiota, especially in the elderly. Here, using the Quantitative Index for Dietary Diversity (QUANTIDD), we analysed the relationships between dietary diversity and gut microbiota diversity in 445 Japanese subjects aged 65-90 years. We also examined the effect of age by comparing the young-old group aged 65 to 74 years (<75 years group; n=246) and the old-old group aged 75 years and older (≥75 years group; n=199). QUANTIDD showed significant positive relationships with Pielou's evenness and Shannon indices, two α-diversity indices related to the uniformity of species distribution. This suggests that a more diverse diet is associated with a more uniform abundance of various bacterial groups, rather than a greater variety of gut bacteria. QUANTIDD also showed significant positive associations with the abundance of Anaerostipes, Eubacterium eligens group, and Eubacterium ventriosum group, which produce short-chain fatty acids (SCFAs) and are beneficial to health. Negative association was found with the abundance of Ruminococcus gnavus group, which produces inflammatory polysaccharides. Positive associations between QUANTIDD and α-diversity indices or the abundance of specific bacterial groups were identified among all subjects and in the <75 years group, but not in the ≥75 years group. Our results suggest that dietary diversity contributes to the diversity of the gut microbiota and increases the abundance of SCFAs-producing bacteria, but only up to a certain age. These findings help to understand the complex relationship between diet and gut microbiota, and provide hints for specific dietary interventions to promote beneficial gut microbiota in the elderly.

Characteristics of gut microbiome, organic acid profiles and viral antibody indexes of healthy Japanese with live Lacticaseibacillus detected in stool

To estimate the health-promoting effects of Lacticaseibacillus paracasei (previously Lactobacillus casei) strain Shirota (LcS) that reached the lower gastrointestinal tract alive, we investigated the characteristics of gut microbiome, organic acid profiles, defecatory symptoms and serum viral antibody indexes of healthy Japanese adults between the group in whom live LcS was detected or not from stool. The β-diversity index of the gut microbiome constituted a significant difference between the live-LcS-detected-group (LLD) and the live-LcS-not-detected-group (LLnD). In the LLD, the Bifidobacteriaceae, Lactobacillaceae, and Coriobacteriaceae counts were significantly higher, and the succinate concentration was significantly lower than that in the LLnD. The serum herpes simplex virus (HSV) immunoglobulin (Ig)M antibody index in the LLD tended to be lower than that of the LLnD in HSV IgG-positive subjects. Of the LLD, those in the fermented milk products containing LcS (FML)-high-frequency-group (FML-HF) and those in the FML-low-frequency-group (FML-LF) had different gut microbiome and organic acid profiles. However, the pattern of differences between FML-HF and FML-LF was dissimilar those between LLD and LLnD. In contrast, among subjects with FML-LF, those in the group with LLD in stool (LF-LLD) and those in the LLnD in stool (LF-LLnD) showed a similar pattern of differences in their gut microbiome and organic acid profiles as those in the LLnD and LLD. The LLD and LF-LLD commonly had lower caloric and carbohydrate intakes from the diet than their respective control groups. In this study, we found that the presence of live LcS in stool is associated with a healthy gut environment and inhibition of the reactivation of latently infected viruses in the host. However, these health-promoting effects on the host were not related to the frequency of FML intake. Furthermore, dysbiosis of the gut microbiome and diet including caloric intake was related to the viability of ingested LcS in the gut.

Association of life habits and fermented milk intake with stool frequency, defecatory symptoms and intestinal microbiota in healthy Japanese adults

Few studies have examined the effects of smoking habit, the frequency of alcohol drinking, exercise, and fermented milk consumption on defecatory symptoms and gut microbiota composition, and particularly their interactive effects. We examined the effect of these lifestyle factors on bowel movements and gut microbiota composition in 366 healthy Japanese adults by analysis of covariance. Smoking did not affect defecatory symptoms but was negatively correlated with total bacteria and Enterococcus counts. Drinking frequency was significantly positively correlated with a feeling of incomplete evacuation and counts of the Bacteroides fragilis group and Acidaminococcus groups. Exercise frequency tended to be negatively correlated with the Bristol Stool Form Scale score and was significantly negatively correlated with the counts of Enterobacteriaceae and positively correlated with the Prevotella counts in the faeces. The frequency of fermented milk consumption was not significant but tended to be positively correlated with stool frequency. The frequency of fermented milk consumption was significantly positively correlated with the counts of the Atopobium cluster, Eubacterium cylindroides group, Acidaminococcus group, Clostridium ramosum subgroup, and Lactobacillus in the faeces. The frequency of consumption of probiotic Lactobacillus casei-containing fermented milk was significantly positively correlated with stool frequency. The counts of probiotic Lactobacillus casei in the stool was positively correlated with the counts of Bifidobacterium and total Lactobacillus. These results suggest that smoking, alcohol drinking, exercise, and consumption of fermented milk, particularly containing probiotic L. casei, differently affect bowel movements and gut microbiota composition in healthy Japanese adults.

Habitual intake of fermented milk products containing Lactobacillus casei strain Shirota and a reduced risk of hypertension in older people

This study investigated relationships between the frequent intake of fermented milk products containing Lactobacillus casei strain Shirota (LcS) and the onset of hypertension (resting systemic pressure ≥140 mmHg [systolic]/≥90 mmHg [diastolic], a doctor’s diagnosis and/or antihypertensive medicine use) during a 5-year period in 352 communityliving Japanese aged 65 to 93 years (125 men and 227 women). Initially normotensive subjects were divided into two groups (n=254 and n=98) on the basis of their intake of fermented milk products (<3 or ≥3 times/week, respectively), as estimated during an interview by a certified nutritionist. The incidence of hypertension over the 5-year interval was significantly lower in those who took fermented milk products ≥3 rather than <3 times/week (6.1 vs 14.2%, P=0.037). A multivariate-adjusted proportional hazards model predicted that blood pressures were significantly more likely to remain normal over 5 years in subjects who took ≥3 fermented milk products rather than <3 times/ week (relative risk 0.398 [95% confidence interval 0.167-0.948], P=0.037). These results suggest that after adjustment for potential confounders, the risk of developing hypertension is substantially lower in elderly people who take fermented milk products containing LcS at least 3 times a week.