Fiber and Fermented Foods: High Marks for Your Gut Health

An F may mean failure in school, but the letter earns high marks in your diet. The two biggest dietary Fs—fiber and fermented foods—are top priorities to help maintain healthy digestion, and they potentially offer much more.

The Gut Microbiome

The gut microbiome is composed of bacteria, viruses, fungi, and other microorganisms living in the colon (large intestine). What you eat, the air you breathe, where you live, and many other factors affect its makeup. Some experts think of it as a hidden organ because it helps the immune system function optimally, reduces chronic inflammation, keeps intestinal cells healthy, and provides essential micronutrients not included in a regular diet. Your gut communicates with your brain through the gut-brain axis, and changes in the microbiome have been linked with mood and mental health disorders such as depression and anxiety. However, it’s not yet clear that these changes directly cause these problems. We do know that a healthy diet low in processed foods is key to a healthy gut microbiome, and increasing evidence suggests that fiber and fermented foods can play important parts here.

Benefits of Fiber

Fiber’s main job is to make digestion smoother by softening and adding bulk to stool, making it pass quickly through the intestines. But fiber has other benefits for your microbiome and overall health:

A high-fiber diet helps keep body weight under control.
It lowers LDL (bad) cholesterol levels.
Eating enough fiber reduces the risk of heart disease, type 2 diabetes, and some cancers.

There are two types of fiber:

Insoluble fiber helps you feel full and encourages regular bowel movements.
Soluble fiber helps lower cholesterol and blood sugar.

Recent research suggests focusing on total fiber intake rather than type. To add more fiber-rich foods, ease into new habits and drink plenty of water to avoid gas, bloating, diarrhea, and cramps. Your body will adjust after about a week. Aim for 14 grams of fiber for every 1,000 calories consumed, but instead of tracking fiber daily, focus on adding more servings of fiber-rich foods.

Fiber-Rich Foods

Fruits
Vegetables
Legumes
Nuts and seeds
Whole grains

Over-the-counter fiber supplements—capsules, powders, or chewable tablets—can be used occasionally if you have trouble eating enough fiber, but they should not be your primary source.

Fermented Foods and Probiotics

Fermented foods contain both prebiotics—ingredients that create healthy changes in the microbiome—and beneficial live bacteria called probiotics. Both support healthy digestion, nutrient absorption, and a strong immune system.

Many fermented foods undergo lacto-fermentation, where natural bacteria feed on sugars, creating lactic acid and good bacteria species such as Lactobacillus and Bifidobacterium. Note that some processes—like brewing beer or canning—can remove or inactivate probiotics. Fermented foods may also contain enzymes, B vitamins, and omega-3 fatty acids.

There is no recommended daily allowance for prebiotics or probiotics, so aim to add more fermented foods to your daily diet.

Popular Fermented Foods

Yogurt (look for “live and active cultures” on the label)
Kimchi
Sauerkraut
Kombucha
Pickles

Probiotic supplements are available, but they are not FDA-approved to guarantee strain counts or benefits. It is best to get your probiotics from fermented foods.