Bugs in Our Guts

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Two recent research studies contribute to the growing body of evidence that the population of microbes residing in our intestines plays vital roles in our health. One is a meta-analysis of studies done to determine if taking probiotics alongside antibiotics can alleviate antibiotic associated diarrhea; results are reported in the Journal of the American Medical Association [1]. The other evaluated the effects of red wine on the different species of bacteria in the gut; it appears in the American Journal of Clinical Nutrition [2].

Gastro-intestinal health

As many as 30% of people taking antibiotics suffer from diarrhea due to the disturbance of their gastrointestinal flora, and this symptom is a primary reason that people prematurely halt their antibiotic treatment. Susanne Hempel and colleagues at the Southern California Evidence-Based Practice Center gathered data from 63 randomized controlled studies of probiotic use, covering 11,811 individuals, and concluded that probiotic administration did, in fact, significantly reduce the incidence of antibiotic associated diarrhea. Most of the studies used probiotics as a preventative measure, although a couple used them as treatment for diarrhea that had already commenced. But most used a blend of probiotics, so the researchers were not able to tease out the individual contributions of each one. The authors note that future studies are needed to figure out which probiotics are the best for which patients, and to identify any potential negative effects of taking probiotics.

While study participants in the above meta-analysis formed a large and heterogeneous group, the other research study was quite small; it involved only ten healthy men between the ages of 45 and 50. Based on the premises that phytochemicals are found in red wine and that phytochemicals can modulate the composition of the gut microbiome, the goal of this study was to measure the effect of red wine on a specific group of gut microbes. Study subjects had their fecal microbiota analyzed after consecutive 20 day periods of drinking red wine, de-alcoholized red wine (phytochemicals with no alcohol), and gin (alcohol with no phytochemicals). Daily consumption of red wine, with or without alcohol, significantly increased the number of many beneficial species of bacteria in the gut while exhibiting antimicrobial effects on pathogenic bacteria. Wine also had positive effects on other parameters: it caused blood pressure and triglycerides, HDL and total cholesterol, and C-reactive protein (a marker of inflammation) to go down significantly. Gin changed the fecal microbiome, but not the other parameters. The authors suggest that the reduction in these important indicators of heart health were a direct result of the wine’s increasing the growth of two specific genera, Bacteoides and Bifidobacterium, in the gut. This study provides good evidence that diet can change the population of gut microbiota in healthy individuals, and that red wine can act as a prebiotic — an agent that can boost the population of beneficial bacteria in our bodies.


  1. Hempel et al. Probiotics for the prevention and treatment of antibiotic-associated diarrhea: a systematic review and meta-analysis. JAMA. 2012 May 9;307(18):1959-69.
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  2. Queipo-Ortuno et al. Influence of red wine polyphenols and ethanol on the gut microbiota ecology and biochemical biomarkers. Am J Clin Nutr. 2012 Jun;95(6):1323-34. Epub 2012 May 2.
    View abstract
About the Author

Diana Gitig, Ph.D., is a freelance science write based in White Plains, New York. She earned her Ph.D. in Cell Biology and Genetics from Cornell University's Graduate School of Medical Sciences.