Probiotics, healthy bacteria that live naturally inside our bodies, can be boosted through food or dietary supplement intake to support our health. It’s no surprise that bottles of probiotic supplements are appearing in more and more medicine cabinets and refrigerators.

In February 2017, Consumer Lab reported that probiotics are the fourth most popular supplement, right behind vitamin D, fish oil, and coenzyme Q10, based on a study of more than 9,000 supplement-taking individuals. Two years ago, probiotics had the number eight spot. But this year, probiotics even surpassed multivitamins in popularity.

But what about prebiotics — probiotics’ trusty sidekick? Prebiotics actually help probiotics work more effectively by serving as food and fuel. With all the attention probiotics have garnered, it’s easy to forget about prebiotics. Consider this your guide to understanding what both are, how they differ from each other, and why you need them both.

Probiotics 101
Bacteria and microorganisms outnumber human cells by 10 to 1. Probiotics are naturally-occurring type of “good” bacteria in the body. We’ve talked before about how to choose the right probiotic supplement and how they support your gut health. You can get more of this healthy bacteria by taking a probiotic supplement or eating fermented foods like yogurt, sauerkraut, kefir, or kimchi.

Probiotics restore the good bacteria in your body in case of sickness or infection, when the “bad” bacteria takes over and causes imbalance. In addition to fighting off unhealthy bacteria and keeping our immune systems strong, the microorganisms can promote nutrient absorption and aid digestion.

Preliminary research suggests probiotics may relieve digestive symptoms like diarrhea and irritable bowel syndrome (IBS), too, as well as help maintain optimal oral and vaginal health. There are many different types or “strains” of probiotics that serve various purposes; research shows that the “lactobacillus” strain, for example, can support our guts and vaginas.

Prebiotics 101
According to the Mayo Clinic, prebiotics are a non digestible fiber that serve as food for probiotics. Probiotics in our body eat prebiotics and use them as fuel. Prebiotics nourish probiotics, and allow them to proliferate on their own and do their job, as described above.

In other words, in order for probiotics to work, they need prebiotics. Think of it like this: say you buy a bunch of new plants for your home. That’s a great first step, but the plants must be watered in order to survive. In this example, the plants are probiotics and the water is prebiotics.

Before you go out and buy a prebiotic supplement, keep in mind that they are naturally available through a wide-variety of common foods like asparagus, dandelion greens, oats, seaweed, garlic, leeks, flax seeds, apples, bananas, and even cocoa.

The bottom line
Probiotics and prebiotics are quite different — one is bacteria and the other fiber — but they work hand-in-hand. But before you consider making changes to your diet or supplement routine, check in with your doctor or a specialist to fully understand your body’s needs — everyone’s different.

Ultimately, getting enough probiotics and prebiotics through food or a supplement ensures the good bacteria in your body is present and functioning, so you can reap the health benefits.

English Taylor is a San Francisco-based women’s health and wellness writer and birth doula. Her work has been featured in The Atlantic, Healthline, Refinery29, NYLON, and Modern Fertility. Follow English and her work at https://medium.com/@englishtaylor or on Instagram at @englishtaylor.