Diverse diets enrich gut microbes
Mark Heiman, from MicroBiome Therapeutics in New Orleans, LA, and Frank Greenway, from Louisiana State University in Baton Rouge, LA, explain that over the last 50 years, by reducing agro-diversity, changes in farming have reduced dietary diversity.
More and more research is revealing the important role that the vast colonies of bacteria and other microbes that live in the gastrointestinal tract play in health and disease.
Healthy people, note the authors, have a diverse range of species in these gut microbe populations - collectively referred to as the gut microbiome - while many of our 21st century diseases - such as type 2 diabetes, obesity and inflammatory bowel disease - are linked to reductions in this richness.
Scientists are beginning to suggest we should view the gut microbiome - whose cells outnumber our own - as an organ in its own right, because without it, we could not metabolize some of the nutrients we need from the food we eat.
Moreover, the microbiome also produces unique compounds that convey signals important for the body's metabolism - the set of chemical reactions that go on inside our cells that keep them working and alive.
It follows, argue Heiman and Greenway, that if a varied diet becomes more specialized, then over time, this will change the gut microbiome. In fact, they note, it only takes a few days following a change in diet for the microbe population in the gut to change.
It also follows, that if we adhere to a diet that cuts out certain types of food, then we could also be changing - and perhaps diminishing - the species diversity of our gut microbiome.
Will stool specimens overtake blood tests?
The authors explain that the richness of the species diversity of the microbiome affects not only the availability of nutrients, but also the richness of different types of signal between the gut and the rest of the body that can affect health and disease.
One of the examples they give is a compound called phosphatidylcholine, which is abundant in foods such as shellfish, eggs, milk, red meat and poultry. Gut microbes convert this compound to trimethylamine (TMA).
The TMA is absorbed by the host and oxidized to form another compound called trimethylamine-N-oxide (TMAO), which is linked to the artery disease atherosclerosis.
However, explain the authors, if the diet also contains food common to Mediterranean diets, such as balsamic vinegar, red wine, cold-pressed extra virgin olive oil or grapeseed oil, then the body will also ingest an inhibitor of TMA production.
Heiman and Greenway conclude that the importance of microbiome diversity cannot be overstated; the microbes produce a huge range of molecules for our bodies. If that range is increased, then we have a large repertoire of physiological responses, allowing us to adapt easily.
They also propose that the future of personalized medicine for metabolic diseases may lie in understanding how specific components of a diet affect a person's gut microbiome, and suggest:
"In the future, an adult seeking treatment for obesity may be surveyed about dietary preferences and present a stool specimen."