Microbiome at a Glance
- Definition: Your microbiome is the community of all the bacteria and other microorganisms living in and on you – most of them in your gut.
- Distinction: "Gut flora" is the everyday term for it. "Microbiome" is the more precise scientific term: it covers not just the bacteria themselves, but also their genes – everything these bacteria can do and produce.
- Scale: Your gut is home to an estimated 100 trillion microorganisms from around 400 different bacterial species – about 95 percent of them live in your large intestine.
- Individuality: Your microbiome is as unique as a fingerprint – and it keeps changing throughout your life.
- Influencing factors: Diet, lifestyle, medication, and environment all shape which bacteria thrive in you.
- History of the term: The word "microbiome" emerged in 2001 in the context of genome research and has been standard in science ever since – though microorganisms in the body were first discovered back in the 17th century.
What is the Microbiome?
Your microbiome is the sum of all microorganisms living in and on you: bacteria, fungi, viruses, and more. The largest and most important community of these lives in your gut – your gut microbiome. Your gut is home to an estimated 100 trillion microorganisms from around 400 different bacterial species, with about 95 percent of them living in your large intestine. But your skin, mouth, and other parts of your body have their own small communities of microorganisms, too.
Sounds like a crowded picture book of bacteria – but above all, it's useful. These tiny roommates – together known as gut flora or microbiome – help you do things like break down food your body can't manage on its own, and they stay in close contact with your immune system. Strictly speaking, "gut flora" refers only to the bacteria themselves, while "microbiome" also includes their genes – in other words, what these bacteria can do and produce, like certain vitamins or digestive helpers. For everyday purposes, though: both terms are really talking about the same thing.
How the Microbiome works
Picture your gut as a small, well-organized city. Different groups of bacteria have different jobs: some break down parts of your food that your body can't process on its own – fiber, for example – and turn them into substances that nourish your gut lining. Others stay in constant contact with your immune system.
What this "city" looks like is different for everyone – shaped by your birth, what you ate as a baby, and later by your own personal habits. More important than individual "good" or "bad" bacteria is diversity: the more different residents your microbiome has, the more balanced it's currently considered to be in research.
Microbiome and Diet: What helps it thrive
What you eat helps determine which bacteria can thrive in you. Eating a very one-sided diet over time can reduce the diversity of your microbiome. Eating a colorful, varied diet, on the other hand, gives it more to feed on – quite literally.
Fiber, fermented foods & diversity
Fiber from vegetables, whole grains, and legumes is basically the favorite food of many gut bacteria – experts call it prebiotic for that reason. Fermented foods like sauerkraut, kimchi, or yogurt add live microorganisms on top of that. As a rule of thumb: it's better to eat colorfully and plant-focused than to rely on a single "superfood."
Tea, polyphenols, and the gut – What the research says
Tea plays a role here too – mainly because of its polyphenols, plant compounds known for their high antioxidant activity. Here's the interesting part: a large share of these polyphenols reaches the large intestine undigested, coming into direct contact with your microbiome there.
An honest note on this: early studies, mostly conducted in the lab, observe that polyphenols from green tea can change the composition of certain bacterial groups in the gut. What that actually means for your health hasn't been established yet – research on this is still in its early stages, and the amounts used in these studies are often far higher than what you'd get from drinking tea normally. What you can rely on, though: unsweetened teas contribute to your daily hydration, and the caffeine in tea tends to feel gentler than pure coffee caffeine, thanks to its natural pairing with L-theanine.
A Brief History: From "Gut Flora" to Microbiome
Back in 1683, Dutch naturalist Antonie van Leeuwenhoek used a microscope to observe microorganisms in the human body for the first time – in a sample from his own dental plaque. It was the earliest documented observation of microorganisms altogether, though still a long way from today's concept of the microbiome. It was only later that research began to focus specifically on the gut. The bacteria discovered there came to be known collectively as "gut flora" – a name that has stuck around in everyday language ever since.
The term "microbiome" itself only emerged in 2001, in the context of genome research. The idea behind it: alongside your own genetic material, the genes of the microorganisms in and on you also play a role in how your body functions – so scientists began thinking of them as a kind of second, accompanying genome. With the launch of major research projects like the Human Microbiome Project starting in 2007, the topic finally moved into the spotlight – and shortly after, found its way into nutrition, wellness, and everyday vocabulary.
Fun Facts
- Not just at home in your gut: Your skin, mouth, and other parts of your body each have their own, quite different microbiome.
- More genes than you have: The genes of all the microorganisms in your microbiome outnumber your own genes many times over.
- Almost like an organ of its own: Some researchers now jokingly call the gut microbiome a "forgotten organ" – that's how many jobs it takes on.
- As unique as a fingerprint: Even identical twins don't have identical microbiomes.
- Polyphenols take their time: Since they're only really metabolized in the large intestine, they affect your microbiome later than other nutrients do.
- The "overnight fix" myth: Your microbiome can't be "fixed" over a single weekend – its composition tends to change over weeks, through lasting habits rather than a single meal.
