If you're just now grasping how important your gut is [1] is for your overall health, you're not alone. "[Gut health] is really an emerging field," said Christopher Gardner, PhD, director of nutrition services at the Stanford Prevention Research Center. And while much is being discovered when it comes to how the gut works and how it can be optimized, a lot of it has to do with bacteria — the "good kind," also known as probiotics.

What are probiotics, exactly? If you've heard the buzzy term before, know that probiotics are more than a passing trend — thanks in large part to their excellent digestive properties. These living bacteria already exist in your body, but certain foods and supplements provide additional support, allowing important digestive functions to take place. According to the Cleveland Clinic [2], in addition to keeping your microbiome balanced, probiotics can help fight off germs, prevent and treat dysbiosis (an imbalance of the gut microbes), and help prevent infections. Research also shows [3] they can be beneficial for your immune system.

Still, before you stock up on probiotic yogurt (or other probiotic foods) and supplements, it's important to understand exactly how probiotics work, what probiotics are good for, and how to incorporate them into your own diet.

What Are Probiotics?

"Probiotics are live bacteria and yeasts that are beneficial for our health, especially the digestive system," says registered dietitian, Lauren Manaker. "They work by restoring the natural balance of bacteria in the gut, inhibiting the growth of harmful bacteria, and in some cases, creating a more acidic environment." You can think of them as the "friendly" kind of bacteria, colonizing the gut (which contains hundreds, if not thousands, of bacterial species [4]).

What Are Prebiotics?

Although similarly named, prebiotics are the "types of dietary fiber that feed the friendly bacteria in your gut, helping them to grow and flourish," Manaker says. They aren't living like the microorganisms in probiotics, and they're found in fiber-rich foods, such as fruits, vegetables, and whole grains. However, if you're looking to optimize your gut health, Manaker says both are helpful. "Probiotics and prebiotics work synergistically to maintain gut health," she says. "While both probiotics and prebiotics work towards enhancing gut health, they differ in their nature and function."

What Are Probiotics Good For?

There's lots of benefits to eating more probiotics, and they affect a lot more than gut health. Some of the most notable benefits include:

• Healthy digestion: By keeping the gut microbiome balanced, you may notice better digestion with probiotics. This makes it easier for your body to process and absorb nutrients. On the other hand, an unhealthy microbiome, may contribute to chronic gastrointestinal diseases like constipation, gas, and irritable bowel syndrome (IBS) [5], per the Cleveland Clinic.
• Immune function: A healthy digestive system also means an immune system that can fight against "bad" bacteria and harmful microbes. Studies show [6] that probiotics specifically have promising immunomodulatory properties [7].
• Skin health: Because probiotics fight off bacteria, fungi, viruses and parasites (according to the Cleveland Clinic), it may also help with atopic dermatitis and acne and help you achieve clearer skin.
• Less vaginal and urinary tract infections (UTIs): Although still in its early stages, research indicates [8] that probiotics may be able to help people susceptible to UTIs [9] by balancing the urinary microbiota and gut microbiome [10].
• Weight loss: Studies have linked [11] certain strains of probiotics, most notably Lactobacillus and Bifidobacterium, to weight loss. Manaker adds that eating more probiotics may also lower your risk for "obesity".
• Reduced inflammation: Given that probiotics help strengthen the immune system, they also have significant anti-inflammatory mechanisms, lowering inflammatory biomarkers like C-reactive protein [12] (CRP).
• Mood and cognitive function: According to Harvard Medical School [13], early research indicates that probiotics may be able to (indirectly) boost your mood. Because the brain and gut are connected — namely through the vagus nerve — a happier gut may also mean a happier brain. It's a win-win.

Who Needs Probiotics?

Anyone can benefits from probiotics. But not everyone needs them in the form of a supplement. "Those that eat a diet rich in fermented foods and other items that contain prebiotics and include prebiotic fiber in their diet, may not need supplemental probiotics," she says (this includes people with a balanced gut flora).

In fact, Dr. Gardner says to approach probiotic supplements cautiously. Most supplements only offer one or two different strains of bacteria, and doctors don't currently have a way to know if those are the exact strains your body really needs. Ultimately, it's best to "enhance the diversity and capacity of your gut" overall, Dr. Gardner said, which you can do by eating a variety of fermented foods.

If you do wind up taking supplements, "it's important to note that the type and amount of probiotic that works best can differ from person to person," Manaker tells POPSUGAR. She adds that if you deal with a digestive disorder or have been on antibiotics, you may benefit from probiotics, but as with any new supplement, consult a healthcare professional for more personalized advice.

Probiotic Foods

Plenty of foods are packed full of probiotics, and you might even have them in your kitchen already. Manaker suggest the following, in particular:

• Yogurt
• Sauerkraut
• Kimchi
• Kefir
• Certain types of cheese, like cheddar and gouda

Probiotics Side Effects

Probiotic supplements are typically considered safe to take, but depending on how they're marketed (as drugs, dietary supplements, etc.) they aren't all regulated the same way. One of the biggest risks is getting a harmful microbe mixed in with all the "good" bacteria, per the Cleveland Clinic [14]. This wouldn't be a problem for most people, but it could potentially cause infection in people dealing with illness or taking immunosuppressant drugs. That's why experts emphasize as with any new diet or supplement, it's best to consult your care team so they can take your specific health history into account.

Related:

6 Signs Your Probiotics Are Actually Working, According to Doctors [15]

— Additional reporting by Chandler Plante