You have many bacteria in your body. In fact, you have more of them than you have cells. Most are good for you. The ones found in your gut not only help you digest foods, they work all over your body and can be good for your physical and mental health. 

This is all the microorganisms, including bacteria, fungi, and viruses, that live in our digestive tracts. They help you break down food, turning it into nutrients your body can use.

In the gut microbiome, the “good” bacteria do more than just help with digestion. They help keep your “bad” bacteria in check. They multiply so often that the unhealthy kind don't have space to grow. When you have a healthy balance of bacteria in your gut, it’s called equilibrium.  

Studies have found that if you have too much of a certain kind of bad bacteria in your gut microbiome, you're more likely to have:

• Crohn’s disease
• Ulcerative colitis
• Irritable bowel syndrome (IBS) 

Researchers are looking into new treatments for them that target the bacteria in the gut microbiome.

Some kinds of gut bacteria may be part of the link cholesterol has to heart disease. When you eat foods like red meat or eggs, those bacteria make a chemical that your liver turns into something called TMAO (trimethylamine-N-oxide). TMAO may help cholesterol build up in your blood vessels. Researchers are studying a natural substance called DMB that’s in olive and grapeseed oil. They think it might keep your bacteria from making TMAO.

Too much TMAO also may lead to chronic kidney disease. People who have the disease don’t get rid of TMAO like they should. That surplus can lead to heart disease. Researchers think it’s possible that too much TMAO might make you more likely to have chronic kidney disease in the first place.

Your brain sends messages all over your body. Researchers believe your gut may talk back. Studies show that the balance of bacteria in the gut microbiome may affect your emotions and the way your brain processes information from your senses, like sights, sounds, flavors, or textures. 
Scientists suspect that changes in that balance may play a role in conditions like autism spectrum disorder, anxiety, and depression, as well as chronic pain. 

An unhealthy balance in your gut microbiome may cause crossed signals from your brain when it comes to feeling hungry or full. Researchers think there may be a link to the pituitary gland, which makes hormones that help set your appetite. That gland can affect the balance of bacteria in your gut, too. Some studies on treating obesity are exploring this link.

You get your gut microbiome at birth, and the world around you affects it as you grow up. It’s also influenced by what you eat. That’s why it can be different depending on where you live -- and why you may be able to tilt the balance a bit.

Probiotics are live microorganisms that may have health benefits when consumed. Found in some foods, these are “good” bacteria like the ones already in your gut. They can add to the bacteria in your intestinal tract and help keep everything in balance. But they’re not all the same. Each type works in its own way and can have different effects on your body.

They can make your immune system stronger. They may boost gastrointestinal health, too, especially if you have something like irritable bowel syndrome. Some probiotics also may help ease allergy symptoms and help with lactose intolerance. But because our gut microbiomes are unique, if and how they work can be different for everyone. And some experts feel more research is needed.

You can find them in dairy products like yogurt and aged cheeses. Look on the ingredients list for live cultures of bacteria like bifidobacteria and lactobacilli. They're also in fermented vegetables, like kimchi and sauerkraut, and pickled vegetables, like onions and gherkins.

Think of these as a food source for probiotics. They may help your body take in calcium better and boost the growth of helpful bacteria in your gut.
They’re found in fruits and vegetables, like:

• Bananas
• Onions
• Garlic
• Leeks
• Asparagus
• Artichokes
• Soybeans

You can also get them in foods with whole wheat.

Probiotics can boost the growth of good bacteria, and prebiotics are good for probiotics. When you combine the two, it’s a synbiotic. The idea behind them is to help probiotics live longer. You can make synbiotic combinations with things like bananas and yogurt or stir-fry asparagus with tempeh. 

There may be other ways to change your gut microbiome and treat things tied to its balance. For example, fecal transplants (exactly what it sounds like) change your gut bacteria to treat things like C. diff and ulcerative colitis. A device called deep transcranial magnetic stimulation (dTMS) uses a coil put on the scalp to stimulate the brain and change gut bacteria. It shows promise for treating obesity.