The thought of bacteria living inside us is perhaps repugnant, especially since most people grow up being taught that “germs” are bad; some people even have deeply ingrained phobias about the germs all around them. Yet this truth about the useful presence of bacteria in our bodies has become much more popularly known in recent years, and more people than ever before are aware of the need for “gut health” and its connection to the proper functioning of our digestive systems. 

The research on this topic is still somewhat nascent, but studies are increasingly showing that these helpful bacteria are beneficial beyond just digestive health. Indeed, the symbiotic relationship with the bacteria present throughout our body may very well be the key to our overall health and wellbeing. The term for this collection of bacteria is the microbiome, and the more we understand about the microbiome, the more we as a species may be on the way to better health and longer lives.

What is the microbiome?

A biome, in general, is defined as a community of organisms that share characteristics that make them suited to the environment they live in. The human microbiome, then, is a community of microorganisms that have evolved to thrive inside the human body. These bacteria live and multiply inside of us at the same time as helping perform vital bodily functions.  

Scientists have estimated that the typical human body has something on the order of 100 trillion living and active bacteria. They further estimate that the total amount can be comprised of up to 1000 different species. Amazingly, there may be as many as three times more bacteria and other technically non-human cells in our bodies than actual human cells. Many of these microorganisms have a symbiotic relationship with our bodies or simply coexist; not surprisingly, given the vast numbers, scientists still don’t fully understand the functions of all of them.   

While microbiome refers to the overall community of microorganisms in the human body, it is often used to refer more specifically to the bacteria that live in the digestive system. One of the main reasons for this is that the bacteria living in our digestive system are by far the largest gathering of microorganisms in the body. These bacteria, or microbiota, are sometimes also referred to as “gut bacteria” or “gut flora.” 

How do microbiota benefit the body?

As noted earlier, this area of research is still relatively new for scientists; it’s only been in recent decades that they are beginning to understand the true potential scope of these gut bacteria and all the roles they might play in our health. However, there are several established benefits of microbiota: 

Defense against pathogens: One of the ways microbiota protect us from pathogens (essentially defined as a microorganism that causes disease) is by fully colonizing the spaces they inhabit; by having taken up residence in our gut and by utilizing the available nutrients, they leave little room for foreign microorganisms to thrive. Also, many microbiota release enzymes or other compounds that destroy or impair the ability of pathogens to reproduce or affect our internal systems. 

Intestinal development: Our digestive microbiome forms quickly after we are born, usually within one or two months. It is during this time that the epithelial lining forms in our bowels and begin to secrete a protective mucosal barrier that is “friendly” to beneficial microbiota. This intestinal lining and the microbiome develop simultaneously and ultimately benefit from each other in the process. 

Bolster immune function: When our immune system senses a pathogen, it can create cytokines, special proteins that create inflammation as a means of protection (even though sometimes that inflammation can backfire); some microbiota are able to drive the immune system to trigger this response selectively so that inflammation can be kept in check. Additionally, some microbiota can influence or regulate the production of antibodies used in defense of pathogens; they can also even produce metabolites that are beneficial to immune system cells.

Metabolizing indigestible compounds: Surprisingly, there are some carbohydrate compounds that can only be digested by enzymes released by microbiota; our own cells actually lack these enzymes. Without this microbiota, our ability to digest food for energy would be much less efficient; indeed, one study showed that rodents without sufficient microbiota required 30% more calories in order to maintain their body weight.  

Synthesis of important nutrients: Human cells are unable to produce all nutrients necessary for proper function, so many must come from external sources. But even then, external sources aren’t always sufficient. Microbiota are capable of synthesizing some important nutrients such as vitamin K, vitamin B12, short-chain fatty acids (SCFA), and many others.   

Gut-brain axis: Perhaps the newest avenue of research in terms of microbiota, the gut-brain axis refers to the interplay between the gastrointestinal system and the central nervous system. The chemical pathways between the central nervous system and the enteric nervous system are plentiful, and researchers are beginning to discover links between this interplay and a variety of neurological and psychological conditions like autism, Parkinson’s disease, anxiety, and depression.

Can diet affect one’s microbiota?

One of the consequences of there being so many trillions of microorganisms in our microbiome is that the composition of the whole will look different for different people. Everyone grows up differently, and in fact, even being born vaginally vs a C-section can have an impact on the makeup of gut flora. In addition to the amount of bacteria present, the proportion of different types can be vastly different from one person to the next. As a result, everyone’s microbiome will function slightly differently and will likewise respond differently to different dietary choices. 

In short, research has continued to demonstrate that your diet can indeed affect the composition and effectiveness of your microbiome. However, because of the differences in microbiota from person to person, and the relative difficulty in performing nutrition research, it is hard to make sweeping statements about precisely how diet can have an impact. Much of the new research being done shows that certain foods can even have a different effect from person to person. 

This area of nutrition is fraught with myth and presumption, and it often leaves the prescriptions of self-proclaimed experts in conflict with scientific research. As a result, there is often confusion over what foods are “best” for gut health. Nevertheless, there are some dietary principles that have substantive research to back them up: 

  • Avoid a Western diet: The typical American diet that is high in fat has been shown to negatively affect the growth of some beneficial microbiota.  
  • Mediterranean diet: A Mediterranean diet, rich in healthy fatty acids, includes fruits, vegetables, legumes, nuts, fish, poultry, and olive oil. There is strong evidence that it is a beneficial choice for good gut health. 
  • Protein: In general, sufficient dietary protein has been found to have a positive effect on microbiota health and diversity.
  • Reduce fat: Apart from the potential for cardiovascular disease as a result of a diet high in saturated fat, a high-fat diet can also have adverse effects on gut flora. 
  • Fiber: Non-digestible carbohydrates like fiber are beneficial to microbiota that reside in the colon by stimulating their growth and activity.   

Another major area of dietary health that may have a significant impact on microbiome health is probiotics. Probiotics are fermented foods that contain lactic acid bacteria and typically include items like yogurt and cultured milk products. While research on this topic is still somewhat new, there is some evidence that dietary probiotics may have a beneficial effect on the microbiome by enhancing the gut bacteria that already reside there. There are, however, many new products available for purchase that make claims about the benefits of probiotics that are still unsupported by scientific research. 

Gastroenterology Appointment

The microbiome is a constantly evolving area of study that researchers will continue to explore, but we already know that this community of microorganisms plays a series of important roles in our health. Until more links are found between gut health and therapeutic activities that can positively impact it, we can rely on the knowledge that a diet high in protein and low in saturated fat can have a positive impact on both our gut flora and our overall health.  If you have concerns about your gut health or your digestive health in general, it might be time to talk with a gastroenterologist. Contact Needham Gastro to make an appointment and to learn more about options for improving your digestive health.