Elderly people's microbiomes may contribute to their frailty

The ELDERMET program is a microbiome project in Ireland out of the University College Cork that is attempting to define the elderly microbiome and discover any associations between the microbiome and diseases linked with frailty and old age.  The team has published multiple papers from this project, some of which we have already blogged about, and last week they published another one in the ISME Journal.  In this latest paper the researchers described in fine detail just how the microbiota changes with diet within a geriatric population, and how this is actually independent of where the elderly people live.

The researchers studied the fecal microbiota of 384 elderly subjects over the course of one year.  They noticed immediately that the microbiomes clustered dependent upon whether the person was living in a nursing home or living amongst the general community.    The researchers characterized the microbiota in 4 groups based on a certain characteristics: M1, M2, M3, and M9.  M1 is a group of genera that is present in almost all subjects sampled, so it represents a core microbiome and is composed of genera such as Bacteroides, Alistipes, Parabacteroides, Faecalibacterium and Ruminococcus.   M2 is a cluster that is composed of bacteria that are associated with high-fiber diets and health, and is comprised of Coprococcus, Prevotella and Catenibacterium.  M3 is associated with folks who lived long-term residential care facilities, and consists of Anaerotruncus, Desulfovibrio and Coprobacillus genera.  Finally, M9 consists of other bacteria that were often found, like strains of Bacteroides, Parabacteroides and Alistipes.

The scientists then compared these microbiome groups with health indicators.  They discovered that highly diverse microbiomes were associated with health, especially among those living in the general community.  However, even though living in long term care facilities often increased diversity, having an M3 microbiome was overall associated with negative health.  In addition, the researchers noted that while individual foods were not strongly correlated with any health indicators, ‘healthy diets’ characterized by high fiber intake, were associated with better health than ‘unhealthy diets’.  Finally, when looking at how the microbiome changed over time, it was apparent that entering a nursing home increased the likelihood of shifting the subjects’ microbiomes to the M3 state, which is associated with bad health.  The researchers think this is likely due to the lack of fiber in nursing home food, and the high use of antibiotics.

The authors state that older people have many differences in their eating habits as compared to a normal adult population, like number of teeth, amount of chewing, and intestinal transit time, and all of these things may be contributing to the altered microbiome.    Regardless of these exogenous factors, this study reinforces the notion that lack of diet diversity and high use of drugs in nursing homes may be creating dysbioses that contribute to frailty disease.  If you have loved ones in an extended stay facility we recommend considering supplementing their diet with some fresh vegetables, so as to keep their microbiome from turning against them.

Changes in the microbiome may affect how we age

Betty White has aged so well because of her microbiome.  Photo by David Shankbone, 2010

Many people have researched the microbiome shift between infancy and adolescence, but very few have researched the changes in the microbiome that occur in the elderly.  A new study out of Canada, published in the Journal Microbiome, did just that.  Their results show that the frailty associated with old-age may be related to the bacteria in our guts.

The study used groups of mice that were either young, middle aged, or old.  They then measured the frailty of these mice which, as one would expect, was tied closely with age.  The researchers then studied the microbiome of these mice, as well as the genes expressed by the bacteria, so as to gain an understanding of what the bacteria are actually doing.

The scientists discovered that, when compared to young and middle aged mice, the old mice were abundant in bacteria that could break down simple sugars, but were underrepresented in bacteria that could break down more complex sugars, as well as lactate.  This is important because increased lactate in the stool has been associated with ulcerative colitis and other inflammatory bowel diseases in older humans.  The old age mice also consisted of less bacteria that could produce vitamins B12 and B7.  Both are important vitamins and the lack of B7 has been linked to colon cancer.  Finally, the old-age mice had bacteria that would rapidly degade creatine.  Creatine is known to build muscle, so constantly breaking it down may cause the decrease in muscle mass observed in the elderly.

Clearly there are changes in the microbiome as we age, and these changes must come with some consequences.  As the authors of this paper suggest, perhaps the microbiome holds to key to the difference between aging like a fine wine and aging like moldy cheese.