You’ve heard the old adage that you are what you eat. It makes sense that, like a car, what you put in your tank determines how well your body will run. However, what most folks don’t think about very often is how well you digest all that fuel, which is every bit as important as what you eat.

Lately, you may have heard more about gut bacteria, something known as your intestinal microflora. While harmful bacteria is the stuff of infections and strep throats, some of the bacteria in your digestive tract is actually beneficial. Good bacteria helps protect you from the bad stuff—harmful bacteria and fungal infections that can be the cause of various chronic diseases such as inflammatory bowel disease, cancer, and obesity.

Your good gut bacteria also helps to regulate inflammation and can assist your body in forming vitamin K and certain fatty acids necessary for your health. Essentially, the microflora in your gut helps to maintain a strong intestinal barrier and keeps harmful substances in check.

In Chinese medicine, there are a number of sources of illness, such as strong negative emotions, trauma, poor diet, working too hard, and toxins. A cause of illness that we don’t hear much about anymore in the United States is parasites, like worms and protozoa in your gut, because they’re not much of a problem in developed nations.

However, harmful bacteria such as H. pylori, the bacteria responsible for stomach ulcers, and C. difficile, responsible for chronic diarrhea, are common and can be considered modern-day parasites.

In both traditional Chinese medicine and Western biomedicine, the foods you eat and some lifestyle habits can affect the health of your gut.

For example, a diet consisting of highly fatty foods allows harmful bacteria to flourish.

In addition, antibiotic use is a double-edged sword. Antibiotics kill off the bad bugs that are causing your strep throat or sinus infection, but they aren’t terribly picky. A round of antibiotics can also wipe out or significantly alter the good bacteria that’s keeping your intestinal tract healthy. This is especially true if you take antibiotics for a long time or if you took them regularly as a child.

The good news is that there are things you can do to help cultivate the well-behaved and useful bacteria in your gut.

You may have heard of probiotics, which are foods or supplements that actually contain bacteria that are beneficial to your gut and digestion. Fermented foods should be your first choice for replacing the good bugs your gut needs. They include sauerkraut, kimchi, kombucha tea, kefir, yogurt, tempeh, miso, and non-pasteurized pickled vegetables. You can also take a probiotic supplement, which, if you get the right kind, can be very helpful.

There are, however, some things to know. First, probiotics are easy to find in your local drug store, grocery, or health food store. Often, you’ll see these products kept in a refrigerator to ensure the freshness and viability of the bacteria.

However, the downside is that everyone’s gut biome is different, and as a result, the type you need is very specific. If you end up taking a probiotic that you don’t need, you may see your digestive symptoms become worse. In addition, the quality of your probiotic supplement can be an issue, because the bacteria need to be alive to be of any benefit.

Lately, we’ve been hearing about using prebiotics as a way of improving the health of your gut. Essentially, a prebiotic is something that feeds your good digestive bacteria. While it doesn’t actually replace the good bugs like a probiotic does, it gives them what they need to thrive. Prebiotic foods tend to be high in fibers that are hard to digest, which keeps them in your gut for a bit longer. Some examples of prebiotic foods include legumes of all kinds, oats, banana, garlic, onions, leeks, apples, berries, artichokes, and asparagus.

The bottom line is that you can give your gut a helping hand, boosting the beneficial bacteria with probiotics found in fermented foods and feeding that good bacteria with foods that contain hard-to-digest fiber. When probiotic and prebiotic foods are eaten together, you have a winning combination for intestinal health.