Study under review: Alterations in fecal microbiota composition by probiotic supplementation in healthy adults: a systematic review of randomized controlled trials
The human gut is home to trillions of microbes that work synergistically with the digestive system to synthesize nutrients from compounds we are not capable of digesting, enhance immune function, and even regulate brain behavior (see Study Deep Dives #6 and #16). Unsurprisingly, various diseases such as rheumatoid arthritis, irritable bowel syndrome, obesity, and diabetes have all been associated with specific changes to the microbiome when compared to healthy people.
What defines the microbiome of “healthy” people? Humans harbor more than 1,000 species of bacteria in the gut, with most belonging to the Bacteroidetes and Firmicutes phyla, and there is considerable variation among apparently healthy individuals, owed in no small part to differences in lifestyle, environment, and diet. This marked complexity makes it difficult to separate meaningful patterns from unimportant noise.
Nonetheless, several themes have emerged from population-level analyses, some of which are depicted in Figure 1. These analyses suggest that a healthy gut microbiome is one that provides an abundance of metabolic pathways (i.e. does a bunch of biochemistry that benefits the host), has a diversity and evenness of microbial groups (lots of different bacteria with no single group overpowering another), and demonstrates the ability to resist harm and return to a healthy state after insult. Indeed, at least one study has shown the microbiome of healthy adults is relatively stable (unchanged) over a five-year period.
Reference: Lloyd-Price et al. Genome Med. 2016 Apr.If a healthy microbiome is diverse and stable over time, then what impact does consuming probiotics have? There is evidence suggesting that probiotic therapy is effective at returning a dysregulated microbiome to a healthy one, but evidence of an effect in already healthy humans is weak. The current systematic review sought to evaluate whether consuming probiotic supplements influenced the composition of healthy people’s gut microbiome composition.
A healthy microbiome is diverse, stable, and capable of numerous metabolic functions. A change away from these general traits is associated with various disease states, and probiotic supplementation appears to help with a return towards normality. However, the effect of probiotics in an already healthy gut is not well-characterized. The current study sought to fill this knowledge gap.
Other Articles in Issue #20 (June 2016)
D-fending against dermatitis
Atopic dermatitis, otherwise known as eczema, isn’t an easily treatable condition. This systematic review looked at whether vitamin D supplementation may help reduce the symptoms of atopic dermatitis
Interview: Rick Miller, MSc, RD
Most cows provide milk that contains at least some of a protein called A1 betacasein. Rick explains the difference between A1 and A2 beta-casein, and what benefits may be associated with A2 milk.
Mamas, don’t let your babies grow up to be gluten intolerant
We’ve previously covered peanut introduction in infants, and next up is gluten introduction. These researchers analyzed the changing literature looking at celiac disease risk when gluten is introduced at different times.
Fattening up breakfast for weight loss
Calories are the most important weight loss factor, but not the only one. It turns out that the type of fats you eat may impact your appetite, and this trial tested two fats (CLA and MCT) for that purpose.
Dead, yet active probiotics?
We know that the gut microbiome can play a major role in a variety of conditions, but the specifics are still being teased out. This study tested the effect of one particular strain called Pediococcus pentosaceus LP28, in a heatkilled formulation.
Carnosine for blood sugar control
If you join together the amino acids l-histadine and beta-alanine, you get the dipeptide called carnosine. Carnosine may have a variety of benefits, and this trial tested carnosine’s specific effect on insulin dynamics.
Coenzyme Q10 and chronic fatigue syndrome
Chronic fatigue syndrome is a life-changing condition without many effective treatments. Could daily supplementation with coenzyme Q10 be a simple way to improve symptoms?
Can arachidonic acid work as a bodybuilding supplement?
There isn’t nearly as much research on potential benefits of omega-6 fatty acids as there is on omega-3s. This study looked at the effect of the omega-6 known as arachidonic acid on resistance exercise