Yogurt in the diet of the elderly: a preliminary investigation into its effect on the gut ecosystem and lipid metabolism

The effect of yogurt as a dietary supplement was investigated with regard to the gut ecosystem and lipid metabolism of 12 healthy, elderly people (78.3 +/- 9.8 years, body mass index 23.6 +/- 5.3 kg.m(-2), mean +/- SD). Commercial yogurt with homogenized fruit was prepared by fermenting milk with yogurt specific cultures Lactobacillus delbrueckii ssp. bulgaricus ( strain AY/CSL) and Streptococcus thermophilus (strain 9Y/CSL). The subjects consumed their usual diet (equal to 6279-6698 kJ . d(-1)) over a 2-week baseline period (baseline start to end) and then were supplemented for 4 weeks with 250 g.d(-1) of fruit yogurt. The yogurt was administered in 125 g portions twice per day: at breakfast in substitution of milk and in the afternoon in substitution of tea with milk (test). At the end of the 4-week period the volunteers returned to their usual diet for a further 4 weeks (follow-up). At the end of each trial period no changes were observed in faecal water content, pH, bile acid concentration or cytolytic activity of the faecal water. Throughout the study there was significant variation neither in dietary intake of macro- and micronutrients, nor in the plasma lipids and, during the experimental period, in the counts of the total anaerobic microorganisms, bifidobacteria, lactobacilli, coliforms or enterococci. The only significant difference was observed in the clostridia counts, that decreased (P < 0.05) after the consumption of yogurt. Moreover, this effect was still evident at the end of the follow-up period. Since this last result can be considered a positive modification of the colon ecosystem, as clostridia are involved in the production of putrefactive compounds, it is possible that a yogurt-supplemented diet can maintain and/or improve the intestinal microbiota of elderly subjects.