How to feed your gut

Your gut is home to trillions of microbes forming a complex community called the gut microbiota, composed primarily of both good and bad bacteria.

Good bacteria are found along the entire digestive tract, although most live in the colon (large intestine). “These bacteria help digest food and absorb nutrients, produce molecules that regulate appetite, synthesize some vitamins, and help your immune system function properly,” says Teresa Fung, a registered dietitian with Harvard’s T.H. Chan School of Public Health. “Good bacteria also keep harmful bacteria in check.”

But sometimes the balance between good and bad bacteria in the gut microbiota gets disrupted. Diets high in processed food, saturated fat, red meat, sugar, and alcohol promote the growth of bad bacteria. Exposure to pollution, toxins, and the overuse of medications such as antibiotics, can also cause bad bacteria to proliferate. When harmful bacteria dominate the gut it can lead to inflammation, infections, and digestive issues like bloating, gas, abdominal pain, and diarrhea.

How can you keep your gut balanced and healthy? In large part, it’s about your diet. Eating more probiotics (foods containing good bacteria) and prebiotics (foods that help fuel the growth of good bacteria) are the key.

“While consuming foods that contain either one can support your gut health, you benefit most by including both in your diet,” says Fung. (Probiotics and prebiotics are also available in over-the-counter supplements, but be aware that these are not regulated by the FDA.)

Probiotic foods

Probiotics are live microorganisms found in many fermented foods. There are several types of fermentation, but lactofermentation, in which bacteria naturally found in the food (or deliberately added to it) convert sugars and starches to make lactic acid, is among the most common. The lactic acid helps preserve the food and also adds a distinct tart flavor.

The most common probiotics in fermented foods are from the genus Lactobacillus and the genus Bifidobacterium. Each genus includes various species. On many (but not all) fermented foods, you can find the specific probiotics they contain listed on the label by genus (abbreviated by the first letter) and species. Sometimes the strain (a specific variation of the species identified by letters or numbers) is also added; for example, L. bulgaricus 2038 for Lactobacillus (genus), bulgaricus (species), and 2038 (strain).

How much probiotic food should you eat? “There’s no daily recommendation, so the general guideline is to include as many servings as you can in your regular diet,” says Fung.

Yogurt is the most common source of probiotics in the American diet. Look for the words “live and active cultures” and a list of the bacteria on the label. Some brands have the Live and Active Cultures (LAC) seal from the International Dairy Foods Association, certifying that the product contains at least 100 million live organisms per gram at the time of manufacturing. When choosing a yogurt, Fung recommends watching for added sugars and choosing a low-sugar option.

You can incorporate yogurt into your diet in subtle ways, like mixing it into smoothies and oatmeal. You can substitute plain yogurt for mayonnaise in egg salad or potato salad, and make it the base for sauces, salad dressings, and marinades.

There are other probiotic-rich fermented foods to try, such as kefir (a yogurt-like drink with a tart flavor), kimchi (a spicy Korean side dish often made with cabbage), kombucha (a tea drink with a tangy-tart flavor), miso (a popular Japanese seasoning made from fermented soybeans and brown rice), and tempeh (a cake-like block made from soybeans, with a firmer texture than tofu).

Some aged soft or hard cheeses contain probiotics, provided they’re not heated after they’re made. Examples include Swiss, provolone, Gouda, cheddar, Edam, Gruyère, and cottage cheese.

Prebiotic foods

Prebiotics are dietary fibers that your body can’t fully digest, but that serve as fuel for good bacteria in the gut, helping them grow and thrive. Prebiotics are abundant in many high-fiber foods, such as those found in plant-based diets like the Mediterranean and DASH diets. For example:

• vegetables: asparagus, artichokes, leeks, garlic, onions, sweet potatoes, corn, and pumpkin
• fruits: bananas, apples, and berries
• grains: oats, barley, and whole-wheat products
• legumes: beans, lentils, and peas.

“Following a plant-based diet not only helps increase your intake of prebiotics, but also helps cut down on unhealthy foods that support bad bacteria,” says Fung.

The gut microbiota may be complex, but caring for it doesn’t have to be. A few changes to your diet can go a long way to keeping it balanced and healthy.

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