We’ve all experienced it from time to time: bloating, cramping, gas, and discomfort… All indications of something being not quite right with the digestive department of the body. “Was it something I ate?” you may be asking.

The human body is a very complex system, and sometimes, seemingly the slightest thing might set it askew. Maybe it was a bowl of ice cream, dinner at a new restaurant, or an experimental recipe. Or maybe it’s something that’s a bit more frequent, and too often, you’re seemingly searching for relief.

One of the most probable suspects of common, occasional digestive woes is that there’s an imbalance within your gut bacterial ecosystem, called the microbiota. While not all that appetizing to think about, it is quite fascinating.

Did you know there are 100 TRILLION bacteria living within your gut right now? That’s about three pounds worth. In fact, there are approximately 10 microbes lining your intestinal tract for every cell in your body. That’s a virtual forest living in the gut. These little fellows, called intestinal microbes, feed off of the food that we eat, helping with digestion and absorption, yet they have other very important roles.

For one, they help the immune system function properly. They also help by producing B and K vitamins. And perhaps most important, they consume waste, which prevents pathogenic bacteria from overwhelming the system (or even buying a bit too much real estate). Healthy bacteria, in fact, promote a healthy inflammatory response as well as help promote weight management, appetite control, and healthy carbohydrate metabolism.

As you can see, digestive health is about way more than digestion and absorption or even a little bloating or gas! Healthy bacteria are the good guys in our guts. And we want to make sure we have a healthy balance of them. But how?

A number of factors can upset the balance (leading to an imbalance called gut dysbiosis), including aging, environment, food choices, stress, medications, and more. Fortunately, if you’re looking to support a healthy gut microbiota, one of the first and best places to look is in your fridge.

Here are the top 3 easily digested foods, followed by the top 3 that might just be killing your gut.

The Top 3 Easily Digested Foods

1) Yogurt

You probably knew yogurt would be on the list, but not all yogurt is created equally. And it’s not just a matter of taste. What makes yogurt one of the most easily digested foods? It is the little bacteria, the health-enhancing probiotics, that create it through the process of fermentation. They’re called “live active cultures.” You’ll want to make sure they’re listed on the label and alive and well. After all, by definition, probiotics must be alive when consumed.

The other caveat is a big one: watch the sugar content! Sugar is great… for feeding bad bacteria, which contradicts why you’re eating your yogurt in the first place. Instead, we recommend buying plain yogurt and adding fresh fruit if you prefer it on the sweeter side. Or, use yogurt not as a dessert but as a sour cream substitute. (Try mixing a spoonful with a ripe avocado for a delicious, creamy veggie dip!)

And if you must go with sweetened versions, shoot for 15 or less grams of sugar. Organizations like the American Heart Association recommend consuming less than 25 grams of added sugar, which, when consumed in excess, may contribute to obesity, diabetes, and cardiovascular disease. For an extra boost of protein, choose Greek yogurt. When choosing yogurt, it’s best to go organic, which tends to have more omega-3 fats, fewer omega-6 fats, and more conjugated linoleic acid than conventional dairy.

2) Fermented Veggies

Fermented veggies, like sauerkraut, pickles, and kimchi, are made through the process of lacto-fermentation. As a result, they are robust sources of the all-important the probiotics we’re looking for, including Lactobacillus brevis and Lactobacillus plantarum, which is regarded as one of the top probiotics for inhibiting bad bacteria and promoting health gut function. This is why they own a spot on out list of easily digested foods.

Buyer beware: many store-bought versions of pickles and sauerkraut are pickled in vinegar and do NOT contain live active cultures. So seek your fermented veggies in the refrigerated case, soaking in their own brine (water and salt mixture) rather than in vinegar.

Kimchi is a special type of Korean fermented food. It’s made with cabbage, radishes, onion, and spices—loads of spices. So if you’re in the mood for something spicy and delicious that naturally supplies active cultures, you might want to give it a try.

Sorry, one more caveat: Because fermented veggies are made with salt, if you’re watching your sodium intake, take a look at the nutrition facts panel and enjoy in moderation.

3) Fibrous Foods

While they don’t necessarily supply probiotics, fibrous foods do help support digestion and regularity, and most of us, quite frankly, don’t eat nearly enough. In fact, According to the American Dietetic Association, the average American consumes only about half the recommend daily intake.

Certain fibrous foods also contain “prebiotics,” which help probiotics grow and flourish within our guts by providing the food they love to eat. In addition, fiber helps keep our systems running smoothly, removing waste through and out of our intestines. The best prebiotic-rich foods include garlic, leeks, onions, dandelion greens, asparagus, bananas (particularly green bananas), barley, oats, apples, wheat bran, and jicama.

Veggies, of course, as well as fruits like berries are great sources of fiber as are beans and nuts.

Now that you know our favorite easily digested foods, it’s just as important to know which ones to avoid. Here are a few of the worst culprits to wreck your gut:

These 3 Foods Wreak Healthy Digestion

1) Artificial Sweeteners

Above, we mentioned that sugar feeds bad bacteria. So you might think artificial sweeteners are a better option. Think again. In fact, artificial sweeteners may be even worse. Two recent studies, one in animals and one in humans, found that commonly used artificial sweeteners (i.e., sucralose and saccharin) significantly altered gut bacteria (reducing the good guys) in a short amount of time—in as little as 5 days in humans. Even after weeks of no artificial sweetener use, the beneficial microbes still had not completely recovered balance.

2) High Fructose Corn Syrup

While good bacteria thrive and proliferate with healthy fibers, pathogenic bacteria (the “bad” guys) thrive on sugar—and they like it sweet! They enjoy cookies, cakes, and processed foods, and they seem to be especially fond of the ubiquitous high fructose corn syrup (HFCS), which is used to sweeten everything from soda to salad dressing. Did you know HFCS makes up 42% of all calorie-containing sweeteners? Because regular sugar has similar effects on gut health, it’s often best to leave it on the table too.

If you’re worried that fruits may have the same detrimental effect with their naturally occurring sugars, the fortunate answer is no. Not at all. Because of the way nature packaged these delicious foods with both fiber and antioxidant-rich phytonutrients, they have a positive effect on gut health as mentioned above.

3) Refined and Trans Fats

Refined vegetable oils, which are rich in omega-6 fats, are all too common in the Western diet. And research is showing that this isn’t a good thing. For one, the heavy imbalance in omega fatty acids (too much omega-6, not enough omega-3) has led to a whole host of negative health effects, including, you guessed it, an increase in bad bacteria leading to an unhealthy inflammatory response, making it one of the least easily digested foods

On the other hand, fish oil, which is rich in the omega-3 fats EPA and DHA, has been shown to enrich the gut with beneficial bacteria from the Lactobaccillus and Bifidobacterium families.

Increase the first three easily digested foods in your nutrition plan while decreasing the last three, and your gut will likely thank you. As an extra measure of defense, you may also want to invest in a high-quality daily probiotic supplement. With more and more research demonstrating the positive effects of a thriving probiotic population in the gut, it’s a simple “insurance policy.”