Turns out, when your wizened aunt told you to “trust your gut,” science was actually on her side. A plethora of new research shows that the health of your digestive tract significantly affects your whole body, from your brain on down. If you sometimes feel like your tummy is talking to you, you may be right.

If your belly is so wise, that means it’s important to keep it in good shape. Central to gut health are probiotic bacteria, which have made plenty of headlines in recent years. “Probiotics are live bacteria or microbes that interact with your digestive system,” says Kirsten Shockey, author of Fermented Vegetables and Fiery Ferments (Storey, 2014 and 2017). “We need them in our digestive system for it to function properly.”

The bacteria, yeasts and other organisms that make up what’s known as the microbiome help the small and large intestines process food. They also keep out the bad critters that can cause a host of problems, from digestive issues to short-term and chronic illnesses. “The microbiome is the safeguard of everything,” says Dr. Keith Wallace, author of Gut Crisis (Dharma, 2017).

Humans evolved along with these microbes because the bacteria were present in the fresh and fermented foods that were a regular part of people’s diets. “In the last 50 to 75 years, food has taken a sharp turn away from that,” says Shockey. “Most of the food is very processed and sterile and dead, so our bodies are not getting this regular influx of live new probiotic microbes.”

The good news is that reseeding probiotic microbes in your gut is relatively easy—and getting easier all the time. Grocery stores are beginning to carry a wider array of foods that are full of beneficial bacteria. For people who don’t want to add products like yogurt and sauerkraut to their everyday diet, there are numerous supplements that provide a dose of the microbes your body needs to thrive.

New Research on Probiotics

Although researchers have always known that probiotics were good for the gut, they’re increasingly discovering that probiotics help with more than an upset stomach. “We’re seeing these very broad impacts throughout the body that aren’t associated with the digestive tract, which shows how important [they are] in someone’s overall health,” says Chris Oswald, D.C., L.N., C.N.S., manager of education content for supplement company Nature’s Way.

Data show a connection between a healthy gut and issues such as skin health, metabolic health and a robust immune system. “We know there are certain, very specific probiotic strains that have an impact on the brain and how the body deals with stress or creates more resiliency to the stress of modern-day life,” says Oswald. This has been dubbed the gut-brain axis.

It’s even possible that your digestive system acts as a sort of second brain. “Suddenly the gut is this major player in moods, anxiety, depression and neurological disorders,” says Wallace. “There’s speculation, but with good basis to it, that if you have a craving for a certain food, it doesn’t come from your brain. It comes from your gut.” When yeasts and other bad microbes take up residence in the intestines because there aren’t enough beneficial microbes to fight them off, they can actually produce neurotransmitters and hormones that cause those cravings. “They can short-circuit everything and get what they want,” adds Wallace.

Probiotic Foods

Probiotic microbes need to be replenished regularly. One of the best ways to get beneficial bacteria into your belly is to eat fermented foods, such as sauerkraut, kimchi, yogurt, lacto-fermented pickles, raw cheese, miso and natto, a fermented soybean product common in Japan.

Probiotics can also be consumed in drinks such as kefir and kombucha. A number of companies now press and bottle juices from fermented foods or add probiotic supplements to tonics and flavored waters.

Shockey notes that canning and heating probiotic foods will kill the bacteria. For example, even though sourdough bread is fermented, and the microbes have transformed the ingredients into a more digestible product, it doesn’t contain live probiotics because it’s been cooked. The best place to find probiotic-rich sauerkraut, juices and other foods is the refrigerated section of the grocery store.

The difference between getting probiotics from food instead of supplements is that pills typically contain only a few specific strains of bacteria. “With the live foods you’re getting a broadcast of all kinds of different probiotic bacteria and enzymes,” Shockey says.

Extra-Strength Probiotics: Hoax or Helpful?

It’s also possible to refresh the probiotics in your system by taking supplements. One of the things longtime enthusiasts may have noticed is that companies now offer extra-strength formulas. “Very quickly we moved from 1 billion bug counts (CFUs*) up to 10 billion and 30 billion. Now up to 50 billion is very common,” says Dan Feldkamp with Feldkamp Marketing, a consumer products agency that works exclusively with Kroger and its network of grocery stores.

*CFU stands for colony-forming unit, which refers to the number of live and active micro-organisms that can be found in each serving of a probiotic.

Does the dose really make a difference? Wallace points out that one of the challenges with probiotic supplements is that the bacteria have to be able to survive the stomach’s harsh acids before they reach the large and small intestines. Having a larger number of microbes (as well as higher-quality organisms that can stay alive as they travel through the body) increases the chance that more will reach their final destination.

Oswald says some research shows that extra-strength probiotics can be beneficial. The nuance is that it’s essential to get a bigger dose of the right microbes. There are millions of different strains of probiotic bacteria, and they don’t all offer the same benefits. For that reason, it’s important to work with your doctor to be clear what type of bacteria you need if you’re trying to address a particular problem.

Like any living creature, probiotic bacteria have been assigned a genus and species. But they also have a strain, and that’s what people should be paying attention to when they read labels. “The strain is always that collection of letters and numbers after these big words that most people can’t pronounce,” says Oswald. The strain, not the genus and species, is what’s tied to the results described on the packaging. A pharmacist or medical professional can help.

What’s New: Probiotics for Women and Seniors 

As scientists dial down the specific characteristics of different strains, they can create supplements that benefit certain groups. One of the most popular subcategories right now is probiotics for women. The goal of formulas high in Lactobacillus acidophilus (La-14) and Lactobacillus rhamnosus (HN001) is to decrease the likelihood of urinary tract and yeast infections. “When you take them orally there’s an impact on the vaginal flora,” says Oswald. “When you get it in the right balance, it maintains proper pH and balance. When that gets out of balance, it opens up the possibility of challenges.” (He emphasizes that these formulations are for preventing, not treating, these conditions.)

There are also probiotic supplements made specifically for seniors. As humans age, the natural presence of Bifidobacterium microbes in the gut begins to drop, Oswald says. As this happens, many adults begin to experience problems with regularity. Adding these bacteria back can prop up the population.

A Primer on Prebiotics

It’s not a typo—prebiotics are a similar yet different category to pay attention to. Simply put, prebiotics are fiber-rich materials that provide food for the good bacteria in your gut. Think of them as the fuel that keeps your microbiome strong and healthy. 

All vegetables contain a certain level of prebiotics, according to Shockey. The ones with the highest natural doses are onions and Jerusalem artichokes (also called sunchokes). Both are rich in inulin, a plant-based soluble fiber.

To kill two birds with one stone, ferment your veggies before piling them on your plate. “When you eat fermented vegetables, a lot of the time you’re getting prebiotics and probiotics in the same bite,” Shockey says. 

Prebiotic supplements are also available at the grocery store. They typically come in powder form and must be dissolved in water or another liquid. If that isn’t appealing, “we’re seeing a lot of products that are a combination of prebiotics and probiotics,” says Feldkamp.

Make Your Own

This recipe has its origins in Ecuador: It’s a vinegar-pickled onion. In Ecuador, it calls for cebolla paiteña, a smaller and spicier onion than those we get in the United States. “Our fermented adaptation is delicious,” says author Kirsten Shockey.