The human microbiome: The genome of the 21st century?

It wasn’t until the 1990s that the existence of our microbiome was recognized. These days, the amount of media coverage our microbiome get makes it seem like a big deal. So what’s all the fuss about?

What is the microbiome?

The microbiome is a living ecosystem that exists within (or on) the human body. The term microbiome refers to the genetic material of all the microbes in the human body. A microbe, or “microscopic organism” is a living thing that is too small to be seen with the naked eye. Microbes include bacteria, yeasts, archaea, and other similarly tiny organisms. The average human body contains over 100 trillion microbes, outnumbering our human cells ten-to-one!

Our bodies have several distinct microbiomes that vary depending on location and environment. We have a mouth microbiome, a skin microbiome, a vaginal microbiome – all with a different ‘ideal’ composition of species – plus, of course, the population of gut microbes that inhabits our intestinal tract. For the purposes of this article, I’ll focus on the gut microbiome.

What does the microbiome do?

Until recent years, many viewed bacteria and other microbes as harmful and dangerous; we weren’t aware that these tiny little organisms interact with our human cells in helpful and life-sustaining ways. A healthy, diverse gut microflora helps digest food, protect against harmful pathogenic bacteria and organisms, regulate the immune system and produce vitamins B, K and short-chain fatty acids that are vital for health.

A person’s microbiome influences their susceptibility to infectious diseases and certain chronic diseases including cancer, inflammatory bowel disease, obesity, allergies and autoimmune conditions. It may also influence how a person responds to certain drug treatments and mental health conditions and it influences digestive function.

What is a healthy vs. unhealthy microbiome?

Different people harbour very different collections of microbes, and the microbiome within a person can also vary over time. Scientists are still working to figure out what a ‘healthy’ microbiome looks like, and what causes microbiomes to be different between people. We have some clues but don’t yet understand the full picture.

In general, a healthy microbiome is more diverse with high densities of different classes of microbes. Think of it like a forest – a healthy forest has different species working synergistically to perform different functions that keep the whole system thriving. An unhealthy forest is less diverse, leaving gaps in the system that make it more vulnerable to drought, storms and invasive species.

Adverse health conditions are generally associated with less diversity; this lack of diversity can lead to increases in populations of less ideal (or even harmful) species, greater susceptibility to infections and a poorer ability to bounce back from assaults on the microbiome.

How does diet affect microbiome?

Many factors influence your microbiome, including environmental elements and genetic makeup. Other factors like obesity, stress, antibiotics and infections can also have a negative impact on gut microbiome.

Diet, however, is the single-most powerful way to alter gut microbiome composition. Both long-term and more extreme short-term dietary changes can drastically alter the composition of the microbiome.

To keep your microbes happy and healthy, eat plenty of high fiber plant-based foods like veggies, nuts and seeds, legumes, whole grains, and fruit. The various kinds of fiber in these foods keep the good guys fed. On the flip side, a diet high in refined starches and oils, sugar and processed foods, with limited fruits and veggies tends to starve out the good microbes. Without enough fiber, gut microbes don’t have enough fuel to survive. Alcohol and coffee are also hard on those good microbes, so moderation is key.

What are the consequences of an unhealthy microbiome?

Researchers now believe autoimmune diseases, such as type 1 diabetes, multiple sclerosis, fibromyalgia, rheumatoid arthritis and others, may be associated with dysfunction in the microbiome. IBS (irritable bowel syndrome) and IBD (inflammatory bowel disease) are also closely linked with changes in the microbiome, and connections with depression and anxiety can also be made.

We also know that people who have obesity have distinctly different microbiome compositions than people who have naturally thinner bodies.

Most of the research done to this point has been observational and correlational, meaning the associations between microbiome composition and disease have been linked, but it’s not clear which one came first. Does a change in microbiome composition lead to disease or is it the result of disease?

We do know that differences in microbiome composition cause different people to have differing blood sugar responses to the same food. The microbiome can also influence the concentration of leptin in the body, which can influence appetite.

Can I get my microbiome tested?

Yes! Several companies now offer microbiome testing, but there are a few things to consider before you get it done.

One challenge facing researchers is that there are several different ways to test the microbiome, and different tests may come up with different results based on the same sample. Because of this, the research community is actively working to streamline all testing so that results are more consistent.

Another challenge with testing is that the microbiome is not static – it’s ever-changing. Studies have looked at the gut microbiota daily over 15 months and found the composition changed constantly over the entire period, making it difficult to take a one-time test that accurately quantifies what’s going on. Because of this, serial testing may be more useful to test your microbiome and determine whether changes in diet and environment can lead to a more favourable composition.

Finally, while results may be interesting and provide clues in conditions like irritable bowel syndrome and irritable bowel disease, we haven’t figured out what the ‘ideal’ microbiome composition is, and this ideal composition may be different for every person, so it’s hard to tell how to best manipulate species to be more favourable. We also have yet to figure out how to produce a lasting change in someone’s microbiome.

All this considered, I wouldn’t rule out microbiome testing as an option, although many of the takeaways from testing are still theoretical and experimental.

Reach out to your Copeman dietitian for more information or if you have any questions about your gut microbiome.