What do sauerkraut, kimchi and yogurt have in common? They're some of the best foods you can eat for a healthy gut. That's because they're all sources of probiotics, the good kind of bacteria your digestive system needs. These good bugs do all sorts of important things-like helping you absorb nutrients, fighting inflammation, protecting your intestines from infection and even turning on pathways to your brain.
In fact, growing research shows that the right balance within your body's microbiome-your gut's living, breathing ecosystem, made up of trillions of busy microorganisms-plays a big role in keeping you healthy and happy. Studies suggest it can help protect against stomach problems like inflammatory bowel disease (IBD) and irritable bowel syndrome (IBS), not to mention obesity, colon cancer and other serious conditions. It may even help reduce the risk of depression and anxiety.
Read More: 7 Must-Eat Fermented Foods for a Healthy Gut
But there's a flip side. Just as eating certain foods can help, others can hurt, by feeding the bad bacteria and helping them grow. Here are three not-so-gut-friendly foods to watch out for that may raise your risk for diabetes and heart disease.
1. Diet Soda
Artificial sweeteners in zero-calorie drinks may mess with your microbes, some researchers say. One small study in Israel suggests that sweeteners like saccharine, sucralose and aspartame may alter gut bacteria in a way that increases glucose intolerance, raising the risk of type 2 diabetes. Critics stress that more research is needed-but in the meantime, kicking the diet soda habit can't hurt.
Try This Recipe: Berry-Kefir Smoothie
2. Red Meat
What's bad for your gut can be bad for your heart. Researchers at the Cleveland Clinic recently discovered a surprising link between meat-based diets, gut bacteria and the risk of heart disease. They found that choline-a nutrient naturally found in red meat and eggs (but taken as a supplement in the study)-produced gut bacteria that in turn created a substance known as TMAO, which can lead to hardening of the arteries.
Such bacterial changes can happen fast. In 2013, a Harvard study found that a meat-heavy diet can lead to negative shifts in gut bacteria in as little as two days.
There's more reason to cut back on red meat (and poultry, too): You could be getting antibiotics without knowing it. Meats from conventionally raised animals often contain them. And while you may need antibiotics when you're sick, you don't need them in your dinner. The secondhand drugs can kill off good gut bacteria, allowing the bad kind to thrive, a problem that could potentially lead to antibiotic-resistant superbugs.
If you're a meat lover, consider buying organic. Some "natural" meats are also antibiotic free-but check the label to be sure. It should say "no hormones" and "no antibiotics."
Read More: How Good Gut Bacteria Could Transform Your Health
3. Processed and Refined Foods
Chips, crackers, pretzels and other packaged foods are typically loaded with additives and preservatives-the kind of stuff that throws gut bacteria out of whack. What they generally don't have: gut-friendly fiber, especially the kinds known to feed healthy gut flora. Our advice? Skip the snack aisle and head to the produce section instead.
One last tip: Try to eat different foods every day. More variety on your plate means a more diverse mix of microbes-and that's what your body needs. Trust your gut.
