More than 40% of people around the world experience issues such as diarrhea, constipation, bloating, and other gastrointestinal (GI) symptoms.
These symptoms can be uncomfortable, painful and sometimes embarrassing. The good news is that researchers are learning more every year about the microorganisms living in the gut and how strongly they influence digestion and overall health. Here is an overview of what current science shows.
How gut microbiome affects health
The human body contains trillions of microorganisms, including bacteria, fungi and viruses. These organisms live throughout the body, from the surface of the skin to the intestines.
The greatest number of these microorganisms reside in the digestive tract. Together, they are known as the gut microbiome. Gut microbes contribute to health in several important ways, including:
- Defending the digestive tract against harmful bacteria and viruses
- Helping break down food and absorb nutrients
- Producing certain vitamins the body cannot make on its own
- Supporting immune function and regulating inflammation
A healthy gut microbiome depends on balance, meaning beneficial microbes need to outnumber potentially harmful ones. Research has found links between disrupted gut microbiome and conditions such as irritable bowel syndrome (IBS), inflammatory bowel disease (IBD), allergies, and mental health conditions like anxiety and depression. However, it is still unclear whether changes in gut microbes cause these conditions or result from them.
Supporting the microbes in your gut
Digestive health is closely connected to overall health. Emerging research suggests that prebiotics and probiotics may help influence the balance of gut microbes through diet.
Prebiotics
Prebiotics are foods rich in fiber and resistant starch that nourish beneficial gut microorganisms. Eating these foods regularly helps healthy microbes grow and thrive. These fibers and resistant starches are not digested by the body. Instead, they move through the stomach and small intestine into the colon, where gut bacteria ferment them.
This fermentation process produces short chain fatty acids, vitamins, nutrients and other substances that benefit both digestive health and the body as a whole.
Not all fiber-rich or starchy foods qualify as prebiotics. A food is officially considered a prebiotic only if it is fermented by gut bacteria in a way that leads to specific changes in gut microbiome composition or activity that provide health benefits.
Examples of foods that act as prebiotics include:
- Vegetables such as garlic, onions and leeks
- Whole grains such as oats and whole wheat
- Fruits including bananas and apples
- Cooked and cooled potatoes and rice
- Legumes such as beans, lentils, peas and peanuts
Probiotics
Probiotics are defined as live microorganisms that provide health benefits when consumed in adequate amounts. Probiotic foods or supplements help maintain a healthy balance between beneficial and potentially harmful microbes in the digestive tract.
Most commonly consumed probiotics belong to two bacterial groups, Bifidobacteria and Lactobacillus. Other bacteria and certain yeasts, such as Saccharomyces boulardii, can also act as probiotics.
On food labels, Bifidobacteria and Lactobacillus are often shortened to B. and L., followed by the specific species. For example, L. acidophilus indicates the presence of Lactobacillus acidophilus.
Yogurt and traditional fermented milk products are common sources of probiotics. To potentially provide benefits, the microorganisms in these foods must still be alive when consumed.
Different foods contain varying amounts of live microbes, and some foods lose microbes during processing.
Probiotic supplements
For most people, eating probiotic foods is safe. However, probiotic supplements are generally unregulated, and they are not subject to strict drug-like approval processes; their effects on many health conditions remain unclear. Anyone considering probiotic supplements should speak with a doctor, especially individuals with immune system problems or certain medical conditions.
Situations where a doctor may recommend probiotic supplements:
- When the gut microbiome has been weakened by illness or medical treatment
- After taking antibiotics, to help restore the balance of gut microbes
- For certain digestive issues, such as diarrhea or irritable bowel syndrome (IBS)
- To prevent diarrhea associated with specific infections or treatments
Caring for your gut microbes
Diet and lifestyle choices play a major role in shaping the gut microbiome. The following habits can help support a healthy gut:
- Eat a variety of fruits, vegetables, whole grains and beans. These foods provide fiber that feeds beneficial gut bacteria. Increase fiber intake gradually to reduce gas, bloating and cramping.
- Include fermented foods made with live cultures. Traditional fermented dairy foods can contribute beneficial microbes.
- Limit foods that harm gut diversity. Diets high in fast food, sugar, salt, and processed foods reduce microbial diversity. A diet that is low in fiber and high in fat and animal protein is linked to fewer beneficial gut bacteria.
- Use antibiotics only when necessary. Antibiotics treat bacterial infections but can disrupt healthy gut microbes, sometimes causing diarrhea, nausea or overgrowth of Clostridioides difficile, which infects the large intestine. Even a single dose of a broad spectrum antibiotic can reduce gut bacteria diversity for weeks. Eating fiber rich foods and probiotic foods may help restore beneficial microbes, though medical diagnosis and treatment are sometimes required for C. difficile infections.
- Exercise regularly. Aerobic activity has been shown to increase both the number and variety of beneficial gut bacteria.
- Manage stress. Stress affects the gut brain axis, which allows communication between the gut and the brain. Gut microbes influence neurotransmitters such as serotonin, dopamine and gamma aminobutyric acid, which are important for mood and mental health.
- Get enough quality sleep. Poor sleep can disrupt gut microbiome balance and reduce microbial health.
The trillions of microorganisms living in your gut play a vital role in health and well-being. By eating a nutritious diet and practicing healthy lifestyle habits, you can support a balanced gut microbiome and build a strong foundation for overall wellness.