Your body is filled with bacteria. There are countless numbers of them and they come in various species. That might sound gross, but the bacteria in your body are almost entirely helpful.

Many things can cause a disturbance in the bacterial ecosystem that you carry around. Illnesses, antibiotics, and poor health can all throw your body out of whack. To combat this, probiotics have been recommended more and more.

For many millennia, humans have consumed probiotic foods. They’re basically foods that have gone bad, but instead of spoiling, bacteria formed around them to keep them fresh. Sauerkraut, kimchi, kefir, and fermented pickles are all examples of foods that are preserved by bacteria.

You can eat these (many would say delicious) foods to get these healthy bacteria into your system. Some of the benefits of consuming probiotics include: improved immune function, improved gut health, and there’s even some evidence that it can improve mental wellbeing.

Go to any health food store and you’ll see aisles filled with probiotic supplements. If you dislike probiotic foods, or find consuming supplements to be easier, this might seem like a great choice. However, taking a supplement might not be as effective as eating the right bacteria.

One sweeping study found that, while both had some benefit, eating probiotic-rich foods seemed to be slightly better. The Cleveland Clinic agrees, and points out that there’s a fatal flaw with the supplement industry: lack of regulation.

Supplements aren’t checked by any regulating body before they’re sent out to customers. That doesn’t mean supplements are necessarily bad, but you might not be taking exactly what you see on the label. For example, a probiotic product might have less bacteria than advertised, or a different type.

Another thing to keep in mind is that a probiotic food can have a multitude of bacteria, all living in an ecosystem. Ingesting a variety of bacteria is likely beneficial, since your body also has a wide variety living inside of it.

Right now, there’s still a significant debate in the scientific community over the effectiveness of probiotics. Some say they don’t help, some swear by them. The consensus seems to point towards food being more beneficial than supplements, but how much so is unclear. For now, if you take supplements, just make sure they’re from a well-regarded brand. And, if you eat probiotic foods, just make sure they’re not expired!