Good vs. Bad Bacteria: 5 Tips to Improve Gut Health

The gut contains trillions of bacteria (in addition to fungi, parasites, and viruses). This is the gut microbiome, and it plays a big role in your health. In fact, the body contains more microbial cells than human cells. And there’s actually a lot of evidence that these microbes influence your health, including weight, immune function, and moods.

Scientists are still learning about the microorganisms in the gut. But they do know that certain types of bacteria can make you sick, while other types play an important role in keeping you healthy. Research also shows that diversity (having a lot of different types of bacteria) is important and can even help keep harmful bacteria under control. 

Read on to understand what it means to have a healthy microbiome and the difference between “good” and “bad” gut bacteria. We’ll also share some tips on how to keep your microbiome healthy and diverse.

What are healthy bacteria?

There are a lot of good bacteria that you need to stay healthy. These bacteria live in the intestines and help you digest food and absorb nutrients. They also make vitamins, prevent bad bacteria from causing infections, and may even help boost your immune system.   

While researchers are still learning exactly how bacteria provide health benefits, they know that it likely has to do with what they absorb and produce. For example, good gut bacteria help produce:

• Short-chain fatty acids

• Amino acids, including arginine and glutamine

• Vitamins, including vitamin K and folic acid

Good bacteria can also make it harder for bad bacteria to grow, by crowding them out of the gut. 

Benefits of good bacteria

There’s much more to learn about the complexities of the microbiome. At the moment, there’s evidence that good bacteria in the gut may have many health benefits, including:

• Improving digestive health in people with irritable bowel syndrome (IBS) or inflammatory bowel disease (IBD)

• Helping immune function

• Regulating appetite and weight

• Influencing symptoms of depression

• Helping cardiovascular health

• Preventing cancer

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Examples of good bacteria

There are many different types of good bacteria — microbes that seem to have health benefits. Common examples include: 

• Akkermansia

• Bifidobacterium

• Lactobacillus 

There’s also evidence that having a diverse microbiome, with many different types of good bacteria, may be important for your health. 

What are probiotics?

Probiotics are live microorganisms — like good bacteria — that may have health benefits when you ingest them. These are bacteria or yeast that you can get in food or drinks or take as a pill or capsule. 

Common probiotics include: 

• Lactobacillus acidophilus

• Lactobacillus bulgaricus

• Lactobacillus casei

• Lactobacillus gasseri

• Lactobacillus plantarum

• Bifidobacterium bifidum

• Bifidobacterium lactis

• Bifidobacterium longum

• Saccharomyces boulardii

• Streptococcus thermophilus

Can bad bacteria make you sick?

Yes. Some bacteria can make you sick, like Escherichia coli and Salmonella. When bad bacteria grow and produce toxins, this can cause severe symptoms like abdominal pain, fevers, and diarrhea. Others may cause more subtle but ongoing symptoms, like bloating or irregular bowel movements.

Examples of bad bacteria

Some gut bacteria can have harmful effects on your health. These include:

• Clostridium difficile (C. diff)

• Eschericihia coli (E. coli) 

• Salmonella

• Shigella

• Staphylococcus

These bacteria can grow in the intestine and release toxins, leading to symptoms like abdominal cramping, diarrhea, and nausea. 

How do bad bacteria get into your body?

Some bad bacteria (like C. diff) already live in your gut in small, harmless amounts. They can cause problems if they have the opportunity to grow into large numbers. This can happen when you don’t have enough good bacteria to stop the bad bacteria from taking over. Taking antibiotics is one reason this can happen. 

Harmful bacteria can also get into your body if you eat contaminated food or touch a contaminated surface and then put your fingers in your mouth.

Signs your gut needs more good bacteria

Signs of an unhealthy gut microbiome may range from gastrointestinal (GI) symptoms to symptoms that may seem unrelated to the GI tract. 

These can include:

• Abdominal bloating or cramping

• Diarrhea or constipation

• Weight gain or weight loss

• Fatigue or sleep disturbance

• Rashes or other skin conditions

• The development of chronic disease, such as autoimmune conditions

• Food allergies or intolerance

5 ways to improve gut health

The good news is there are ways that you can start improving the health of your gut. This mostly involves focusing on your diet and lifestyle. Here are some ways to get started:

1. Get more fiber in your diet. Fiber helps with the growth of good bacteria. Look for high-fiber foods like fruits, vegetables, seeds, and nuts. Aim to get 30 grams per day.

2. Include fermented foods in your diet. Fermented foods — such as yogurt, sauerkraut, kimchi, and kombucha — have probiotics (healthy bacteria).

3. Consider taking a prebiotic or probiotic supplement. Talk with your healthcare provider to see if prebiotics or probiotics might be good options for you.

4. Include polyphenols in your diet. Examples include berries, coffee, and tea. These can have beneficial effects on health and the gut microbiome.

5. Exercise regularly. Exercise impacts the gut microbiome, increasing healthy bacteria and diversity.

It’s also a good idea to talk to your healthcare provider about your specific concerns. Be sure to review your medications, as some common medications can also influence the gut microbiome, such as NSAIDs (nonsteroidal anti-inflammatory drugs) and proton pump inhibitors. 

Why trust our experts?

Written by:

Christina Palmer, MD

Christina Palmer, MD, is a board-certified family physician with a focus on chronic care management, women’s health, and mental health. She’s the co-author of “Open Heart: When Open-Heart Surgery Becomes Your Best Option.”.

Edited by:

Sophie Vergnaud, MD

Sophie Vergnaud, MD, is the Senior Medical Director for GoodRx Health. A pulmonologist and hospitalist, she practiced and taught clinical medicine at hospitals in London for a decade before entering a career in health education and technology.

Reviewed by:

Sarah Gupta, MD

Sarah Gupta, MD, is a licensed physician with a special interest in mental health, sex and gender, eating disorders, and the human microbiome. She is currently board certified by the American Board of Psychiatry and Neurology.

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