By now, you’ve probably gotten the memo that a little bacteria in your food isn’t always a bad thing. Some foods contain beneficial live microrganisms like bacteria known as probiotics, which are made through the process of fermentation.

Trend watchers say that probiotic foods are among the most fashionable eats in recent years, but there’s actually nothing new about them.

“Our first records of people using fermentation as a way of preserving food go back to 6000 or 7000 BC,” says Gail Cresci, PhD, RD, of the Pediatric Research Center and Department of Gastroenterology, Pediatric and Lerner Research Institutes at Cleveland Clinic.

What is new: Our enthusiasm for and understanding of just how good probiotic foods may be for us.

While researcher Elie Metchnikoff first noted the good health of Bulgarians who drank soured milk more than 100 years ago, his findings were largely dismissed as antibiotic drugs came into vogue, says Cresci. “With the knowledge we now have about the gut microbiome and how important bacteria are for our health, probiotics have resurfaced.”

Probiotic Supplements Vs. Probiotic Foods

There are loads of probiotic supplements on the market, and no doubt, it’s easier to pop a pill than change your diet.

But the health perks of probiotics may lie in part with their interaction with food.

“The benefits people get from fermented foods come largely from improved digestibility, and the nutrients the foods provide,” says Benjamin Wolfe, Ph.D., assistant professor of microbiology at Tufts University. In fact, he says, in many cases fermentation adds nutritional value.

As the bacteria chemically alter the food—i.e. turn milk into yogurt—they secrete enzymes, organic acids, and proteins. Some of the potential health benefits of probiotics may be due to these compounds, says Cresci.

For example, metabolites—waste products—produced by the probiotic bacteria during fermentation include nutrients like blood-clotting vitamin K, according to Wolfe.

Freeze-dried probiotic bacteria in a supplement may not always have the same effect. And probiotic foods fuel your body while providing health benefits apart from their probiotic activity.

Another reason to stick with food: Makers of dietary supplements don’t have to prove that their products are safe or effective.

How Do Probiotic Foods Help Your Health?

Many benefits are attributed to these microbes—improving digestion, boosting immunity, and helping with weight loss, among others. However, the claims may be overblown and more research needs to be done.

Some evidence does suggest that probiotics can help shorten a bout of diarrhea caused by antibiotics, Clostridium difficile (C. diff), a virus, or contaminated food. They may also improve symptoms of irritable bowel syndrome (IBS). But supplements aren't necessary; in many cases, probiotic foods supply enough good bacteria to help.

So what probiotic foods can you try if you’re interested in getting more gut-boosting bacteria? Here are three to consider incorporating into your day:

Yogurt

Yogurt is made when milk has been inoculated with friendly bacteria—usually Lactobacillus bulgaricus and Streptococcus thermophilus—and allowed to rest for several hours at a temperature that invites the microbes to alter the milk’s natural sugar called lactose. That process thickens it and producing the sour, tart flavor you expect from yogurt.

It's also what makes yogurt a good choice for those who can't drink milk because it upsets their bellies. The bacteria break down the lactose, which means yogurt is far less likely than milk to cause bloating, gas, and other digestive discomfort in lactose-sensitive people.

“You’re essentially using microbes to predigest the food; that makes it more pleasant to eat,” Wolfe says.

Look for: Plain yogurts that are made with milk and live active cultures. You can add fruit to sweeten it. If you prefer a flavored yogurt, look for one that’s low in sugar. Even plain yogurt has some sugar, but it's naturally present in the form of lactose. A sweetened yogurt, however, can pack as many as three heaping teaspoons of added sugar.

Use it: Take yogurt beyond breakfast by turning it savory. Top a bowl of plain yogurt with chopped tomatoes and cucumbers, black olives, and a sprinkle of the Middle Eastern herb blend za’atar.

Sauerkraut

The word we now use to refer to it means “sour cabbage” in German, however sauerkraut has been around since the building of the Great Wall of China when workers dined on shredded cabbage preserved in rice wine. Bacteria present on the surface of the cabbage ferment the vegetable’s natural sugars into lactic acid, which inhibits the growth of harmful microbes. In addition to healthy bacteria, sauerkraut is also an excellent source of immune-protecting vitamin C. Kimchi, popular in Korean cuisine, is a similar fermented food. It’s made with cabbage, but also contains other ingredients and is typically spicy.

Look for: Refrigerated products. Shelf-stable varieties are pasteurized, which kills off the healthy probiotic bacteria. A more potent product will be kept cool. It should be made primarily from cabbage and salt, but seasonings like caraway seeds or other vegetables are okay too.

Use it: To add some tart and crunch to a salad or a quinoa bowl with roasted vegetables.  

Tempeh

The process of adding microbial cultures to cooked soybeans results in a dense, chewy cake with a nutty texture, creating a higher-in-protein-and-fiber and some say easier-to-digest meat substitute than vegetarian mainstay tofu.

Look for: Shrink-wrapped plastic packages in the refrigerated sections of health food stores near the tofu and meat alternatives (some conventional grocers are beginning to carry it as well). Some tempehs are made with grains or seeds like barley and flax, which give different types different textures and flavors.

Use it: Slice and marinate for 30 minutes in a mixture of lower sodium soy sauce or tamari, rice wine vinegar, and sesame oil. Pan fry until each side is golden. Serve on top of stir-fried vegetables in place of chicken.