What does our microbiota do for us? Or do to us?
Undoubtedly, we don’t yet have complete answers to these questions. But even the partial answers we do have show a lot of connections between the microbiota and human health.
Wherever we have a native microbiota, those microbes are making it more difficult for pathogens to gain a foothold, at the very least by taking up space and using up resources – the same reasons why weeds have a harder time getting established in a lush lawn than in a bare field. Beyond that passive role, some members of our native microbiota are also known to actively interfere with the survival and/or growth of various pathogens. Sometimes these effects are enough to completely eliminate the ability of a pathogen to colonize the body. At other times, a pathogen may be able to persist at low abundance as part of the microbiota, without triggering disease.
The biochemical versatility of gut bacteria is put to use in helping us to digest certain parts of our diet (especially plant starches and fibers), in transforming foreign molecules such as drugs and pollutants, and in synthesizing amino acids, vitamins, and even signaling molecules used in our brains. These chemical transformations are mostly helpful to us, but not always though! For example, some gut microbes transform phosphatidylcholine and carnitine, which are abundant in meat, into TMAO, a chemical that promotes arteriosclerosis. And even though our pre-agricultural ancestors may have depended on the ability of their gut microbes to extract energy from plant fiber during lean times, a ‘high efficiency’ microbiota that maximizes the energy extracted from the diet may not be helpful now, when the major dietary issue is too many calories rather than too few.
The human microbiota interacts with the immune system in numerous ways that lead to a variety of effects. For example, some specific compounds produced by members of the microbiota have been found that either promote or inhibit inflammation, and some microbial types seem to be consistently associated with inflamed or uninflamed conditions. However, it would be an oversimplification to suggest that any single member of the microbiota determines what the immune system does, or even that a particular type of microbe always has the same effect on its host. It is undoubtedly true, though, that our microbiota is actively, dynamically involved with the regulation of our immune system, and not simply a passive target of immune activity. There is increasing evidence that the types of gut microbes associated with the high saturated fat, high sugar diet that is common in the developed world contribute to chronic inflammation, which in turn is associated with obesity, diabetes and cardiovascular disease.
As with the immune system, the human microbiota is also integral to the regulation of our metabolism, influencing how our muscles, liver and fatty tissue use and store energy - once again, there is a potential connection with obesity and diabetes. Members of the gut microbiota are even likely to influence our emotions and behavior, a conclusion based on microbial synthesis of known neuroactive compounds, on experiments in rodents, and on suggestive correlations in a few human studies. However, this is a very challenging topic to address with studies of human subjects.
Undoubtedly, we don’t yet have complete answers to these questions. But even the partial answers we do have show a lot of connections between the microbiota and human health.
Wherever we have a native microbiota, those microbes are making it more difficult for pathogens to gain a foothold, at the very least by taking up space and using up resources – the same reasons why weeds have a harder time getting established in a lush lawn than in a bare field. Beyond that passive role, some members of our native microbiota are also known to actively interfere with the survival and/or growth of various pathogens. Sometimes these effects are enough to completely eliminate the ability of a pathogen to colonize the body. At other times, a pathogen may be able to persist at low abundance as part of the microbiota, without triggering disease.
The biochemical versatility of gut bacteria is put to use in helping us to digest certain parts of our diet (especially plant starches and fibers), in transforming foreign molecules such as drugs and pollutants, and in synthesizing amino acids, vitamins, and even signaling molecules used in our brains. These chemical transformations are mostly helpful to us, but not always though! For example, some gut microbes transform phosphatidylcholine and carnitine, which are abundant in meat, into TMAO, a chemical that promotes arteriosclerosis. And even though our pre-agricultural ancestors may have depended on the ability of their gut microbes to extract energy from plant fiber during lean times, a ‘high efficiency’ microbiota that maximizes the energy extracted from the diet may not be helpful now, when the major dietary issue is too many calories rather than too few.
The human microbiota interacts with the immune system in numerous ways that lead to a variety of effects. For example, some specific compounds produced by members of the microbiota have been found that either promote or inhibit inflammation, and some microbial types seem to be consistently associated with inflamed or uninflamed conditions. However, it would be an oversimplification to suggest that any single member of the microbiota determines what the immune system does, or even that a particular type of microbe always has the same effect on its host. It is undoubtedly true, though, that our microbiota is actively, dynamically involved with the regulation of our immune system, and not simply a passive target of immune activity. There is increasing evidence that the types of gut microbes associated with the high saturated fat, high sugar diet that is common in the developed world contribute to chronic inflammation, which in turn is associated with obesity, diabetes and cardiovascular disease.
As with the immune system, the human microbiota is also integral to the regulation of our metabolism, influencing how our muscles, liver and fatty tissue use and store energy - once again, there is a potential connection with obesity and diabetes. Members of the gut microbiota are even likely to influence our emotions and behavior, a conclusion based on microbial synthesis of known neuroactive compounds, on experiments in rodents, and on suggestive correlations in a few human studies. However, this is a very challenging topic to address with studies of human subjects.