That’s why balance in your gut microbiome’s composition is so important. A larger variety of microorganisms means your body is likely going to be better equipped to fight harmful pathogens6, Jessie Wong, RDN, a registered dietitian who specializes in digestive health and irritable bowel syndrome, tells SELF. As for what can help with that rebalancing? That’s where probiotics have earned a lofty reputation3.
Why do probiotics get so much hype, anyway?
According to a consensus of an international expert panel gathered to nail down what the term probiotics really means, probiotics are “live microorganisms which, when administered in adequate amounts, confer a health benefit on the host.”7 (Ahem, the “host” is you, by the way!)
When we talk about probiotics, we’re most often referring to dietary probiotics, or those naturally present in food sources. Strains of bacteria—such as Lactobacillus or Bifidobacterium8—are typically used in the fermentation of foods. Some good probiotic sources include:
- Kimchi
- Gochujang
- Sauerkraut
- Miso
- Pickles
- Natto
- Yogurt
- Kefir
When you eat fermented foods, the microbes enter your digestive system. They pass through your stomach, where most of them are killed. The microbes that survive make it to the small intestine, where some of them will pass through. Then they travel to the colon—an environment home to many different species of microbes. The microbes stick around there for some time, depending on your gut’s structure and environment, says Wong.
Once there, the probiotics produce beneficial chemicals9 that support your immune system and inhibit the growth of bad microbes in the gut, Dr. Huttenhower says. They break down fiber (the prebiotics that we’ll talk about later), and the byproducts from that fermentation—which include short-chain fatty acids—help feed your intestinal cells and keep your intestinal barrier healthy, Wong says. That’s important, since a properly functioning barrier serves as a line of defense that keeps harmful bacteria and substances out of your body10.
Along with dietary probiotics, there’s also an emerging class of probiotics called live biotherapeutic probiotics (LBPs)11, Dr. Huttenhower says. These LBPs are in the early stages of development and are “specifically engineered to colonize the gut and be beneficial” to people with specific health conditions, such as inflammatory bowel disease (IBD), like Crohn’s and ulcerative colitis, and Clostridioides difficile infection, he says.
Now, let’s talk more about how prebiotics come into play.
Prebiotics are the nondigested plant fibers, or carbohydrates, from food that the gut ferments to produce beneficial chemicals.
When you consume fermentable fibers, research suggests that they feed beneficial microbes, helping increase and strengthen good guys12 such as Lactobacillus and Bifidobacterium, so that they occupy more surface area in your gut lining, Wong says.
“The goal of a prebiotic is to promote the growth of good bacteria that are already there,” says Dr. Huttenhower. “Prebiotic fibers aren’t absorbed in the stomach or small intestine, so when they reach the colon, microbes feed off them, which ultimately helps them grow.” Ideally, this should make for a diverse and balanced gut microbiome12.
