The Microbiome: Our Invisible Housemate Loves a Plant-Based Diet

The microbiome Our Fascinating Microbiome Whether on our skin, in the mouth, nose, or deep within the gut—microorganisms live alongside us everywhere. The human body is a walking ecosystem, and its microbial cohabitants play a vital role in our health and well-being. The colon, in particular, teems with microbes: it’s home to most of the […]

The microbiome

Our Fascinating Microbiome

Whether on our skin, in the mouth, nose, or deep within the gut—microorganisms live alongside us everywhere. The human body is a walking ecosystem, and its microbial cohabitants play a vital role in our health and well-being. The colon, in particular, teems with microbes: it’s home to most of the over 1,000 known species of bacteria, fungi, viruses, and other microorganisms that make up what we call the gut microbiome or microbiota.

The number of these organisms is immense. Estimates suggest that the human body hosts about as many microbes as it has cells—roughly 36 trillion. Yet bacteria are much smaller than human cells: the difference is roughly comparable to that between a cat and a human.

Despite their tiny size, these microbes are hugely important for our bodies. Most live with us in peaceful coexistence—many in true symbiosis. Probiotic bacteria in particular—those that promote health—play a valuable role in the colon. They break down indigestible plant components like inulin or pectin (known as prebiotics) and convert them into useful substances, such as short-chain fatty acids, vitamins, amino acids, enzymes, and even hormone-like messengers.

These tiny helpers influence our health in a variety of ways: they support the immune system, regulate inflammation, counteract allergies, and can even impact our mental well-being. When large populations of health-promoting microbes like Lactobacillus acidophilus or Bifidobacterium bifidus are present, the entire body benefits. Such microbial diversity has anti-inflammatory and stabilizing effects. If the microbiome becomes unbalanced—due to antibiotic use or a one-sided diet—it can lead to a condition known as dysbiosis. Over time, this may promote chronic inflammatory diseases such as Crohn’s disease.

Short-Chain Fatty Acids: Energy and Protection from Plant Fibers

Our microbes work hard in the colon. One of their most important tasks is producing short-chain fatty acids (SCFAs) from plant fibers—especially acetate, propionate, and butyrate. These SCFAs are not merely metabolic byproducts: they serve essential functions in our health.

Butyrate, for example, is the primary energy source for colon lining cells and supports the regeneration of the mucosal barrier. It also helps form so-called tight junctions—cellular connections that ensure harmful substances don’t pass from the gut into the bloodstream.

If these protective fatty acids are lacking, the intestinal wall can become permeable—a phenomenon known as “leaky gut.” This allows potentially inflammatory substances to enter the bloodstream and burden the immune system.

Studies show that SCFAs like propionate and butyrate stimulate the production of regulatory T-cells, which actively suppress inflammation and may help prevent autoimmune reactions.

You can think of butyrate like a protective coating for the intestinal wall—a kind of invisible shield that strengthens it against harmful agents. Without this barrier, the wall becomes “leaky,” like an old rain jacket full of holes—contributing to chronic inflammation.

Antibiotics: Lifesaving Heroes—with Side Effects

Since Alexander Fleming’s discovery of penicillin in 1928, antibiotics have become indispensable in modern medicine. They’ve saved millions of lives—a true milestone in human history.

However, these vital drugs have a dark side: broad-spectrum antibiotics, in particular, don’t just kill harmful bacteria—they also wipe out many beneficial ones. As much as 90% of the microbiome can be destroyed by an antibiotic course.

This doesn’t just impair digestion—it also weakens the immune system. The result may be digestive issues, increased susceptibility to infections, and long-term dysbiosis.

That’s why antibiotic use should always be carefully considered and ideally supported by a probiotic-rich diet to help restore the gut flora.

Fiber: The Gut Bacteria’s Favorite Food

Our tiny housemates love plants—specifically plant fibers. Dietary fiber, also called roughage, consists of plant-based components that our small intestine cannot digest. Only in the colon do bacteria take over and transform these seemingly useless substances into powerful health elixirs.

Soluble fibers like inulin, pectin, or beta-glucan are especially valuable because bacteria can ferment them easily.

These prebiotics not only encourage the growth of beneficial bacterial species—they also have a positive effect on our metabolism: they slow stomach emptying, promote longer satiety, lower blood sugar levels, and help reduce cholesterol by binding to bile acids, which are then excreted.

Soluble fiber is abundant in fruits (e.g., apples, pears, oranges), vegetables (e.g., carrots, broccoli), legumes, nuts, seeds, and oats. Fermented foods such as sauerkraut, kimchi, kefir, or sourdough bread also provide living probiotics, which directly enrich the microbiome and help maintain its balance.

Insoluble fibers like cellulose or lignin also play an important role. They increase stool bulk, stimulate bowel movement, and shorten the time waste remains in the gut. These fibers are mainly found in whole grains, legumes, vegetables (e.g., cauliflower, mushrooms), nuts, and the skins of many fruits.

An Evolutionary Perspective: Are We Programmed for Fiber-Rich Diets?

Interestingly, research into the diets of our ancestors shows that they consumed significantly more fiber than modern humans. While the German Nutrition Society currently recommends about 30 grams per day, anthropological studies suggest that Stone Age hunter-gatherers ate up to 100 grams daily. This implies our digestive system evolved to thrive on fiber-rich diets.

Traditional food cultures tell a similar story: in rural areas of Africa or Asia, where diets rely heavily on plants, legumes, and whole grains, fiber intake still exceeds 50 grams per day. Remarkably, chronic inflammatory diseases are far less common in these populations than in Western societies—indicating the preventive potential of high-fiber diets.

Unfortunately, average fiber intake in Western countries falls far short of recommendations—in Germany, for instance, it’s around 20 grams per day. This doesn’t just affect digestion—it also impacts the microbiome, which depends on a wide variety of plant foods to stay healthy and active.

A Thriving Microbiome Needs Plant Diversity

The microbiome is no minor player—it’s a central force in our health. The trillions of microbes in our gut influence immune function, digestion, inflammation, and even our mood. A balanced diet rich in both soluble and insoluble fiber is key to nourishing and supporting this complex system.

Short-chain fatty acids like butyrate protect the gut lining, regulate the immune system, and help prevent silent inflammation. A diverse, plant-based diet—supplemented with fermented foods and mindful use of medications like antibiotics—can help maintain a healthy microbiome in the long term.

What Can I Do Today?

The answer is simple and effective: eat more plants—and a wide variety of them!

Studies show that people who consume at least 30 different plant-based foods per week have a significantly more diverse gut microbiome. This diversity is directly linked to better health, lower inflammation, and a stronger immune system.

Practical tip for everyday life: Start with a colorful weekly plan! Set a goal to eat at least five different fruits, five different vegetables, legumes, whole grains, nuts, seeds, and one or two fermented foods each week. A mix of apples, blueberries, broccoli, lentils, oats, and sauerkraut already covers a good portion of the recommended variety—a great start to a vibrant week.

Aim to keep food processing to a minimum. Avoid excessive sugar, alcohol, and highly processed products—they can throw the microbiome off balance. Focus on fresh vegetables and fruits, legumes, whole grains, nuts, seeds, and fermented foods.

Your gut will thank you—and so will your whole body.

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