Gut health has become a hot topic in recent years. Probiotic supplements and gut-friendly fermented foods are finding new fans as evidence accumulates that our health depends largely on the health of the microorganisms that live in our digestive systems. Recent research now suggests that the mix of bacteria in your gut plays a role not only in your risk for digestive conditions such as irritable bowel syndrome (IBS) but also your risk for everything from high cholesterol, diabetes, obesity and mental health and cognitive function. These well-publicized findings have encouraged many of us to start popping probiotic supplements and consuming fermented foods, both of which are said to contain beneficial bacteria.

But maintaining a healthy micro-biome is not as simple as taking a probiotic—in fact, there is no evidence to support taking probiotics for general gut health. Bottom Line Personal asked dietitian and gut health scientist Megan Rossi, PhD, what else can help us achieve good gut health…

Probiotics and prebiotics have similar names but very different functions. Probiotics contain beneficial bacteria. Prebiotics are compounds in the foods we eat that provide nourishment for the beneficial bacteria in our gut—essentially fertilizer for our microbiome. Consuming prebiotic foods is a crucial part of maintaining a healthy microbiome.

Most prebiotic foods are high-fiber. The human body cannot digest fiber, so the fiber we eat makes its way down most of the gut (your digestive system is nine meters long!) where it serves as nourishment for the beneficial bacteria that live mostly in the final 1.5 meters of your gut. When these beneficial bacteria consume fiber, they produce short-chain fatty acids that contribute to gut health and even have been linked with protecting against colorectal cancer and reducing inflammation throughout the body.

Foods especially high in prebiotics: Onions, garlic, chickpeas, artichoke, asparagus, pistachios, almonds, dates, nectarines, dried mango, watermelon.

Caution: Don’t consume these elite prebiotic foods to the exclusion of other options. The very best prebiotic eating strategy is to include a range of different high-fiber foods in your diet, including legumes, nuts, seeds, vegetables, whole grains and fruits. You can eat these prebiotic foods raw or cooked.

Postbiotics are important, too—but postbiotic supplements might not be. If the terms probiotics and prebiotics aren’t confusing enough, you might come across the word postbiotics as well. These compounds, including the short-chain fatty acids mentioned above, are produced by the probiotics in the gut after they feed on prebiotic foods. It’s clear that these postbiotic compounds are beneficial—they’re anti-inflammatory and seem to benefit the immune system, among other potential advantages. What’s less clear: Whether postbiotic supplements are beneficial. Research is ongoing, but the evidence thus far is not encouraging. One theory is that postbiotics taken in supplement form must pass through the stomach before reaching the gut—and stomach acids might do substantial damage to them. For the time being, the best way to benefit from postbiotics seems to be to ingest prebiotics and allow the microbiome to generate postbiotics…not to take postbiotics in pill form.

Don’t just eat lots of plants…eat a broad range of plants. First, nutritionists instructed us to eat lots of vegetables…then they told us to eat a “rainbow” of different vegetables—vegetables of different colors tend to contain different healthful phytonutrients. Now it turns out that even eating that rainbow of vegetables doesn’t necessarily provide our gut with everything it needs to thrive. Rather than focus exclusively on vegetables, strive to eat many different types of plant-based foods. The ideal daily diet for the gut includes foods from each of six different plant groups—vegetables, fruits, whole grains, legumes, nuts/seeds and herbs/spices. We now know that consuming this range of plants fosters different types of beneficial bacteria in the gut, and that diversity of bacteria is a crucial component of good gut health. In fact, research conducted at Norway’s University of Bergen has linked eating a wide range of different types of plants to longer lifespans.

Workouts work for your microbiome. Exercise can improve the composition and production of beneficial bacteria in your gut, according to multiple studies, including one by researchers at France’s Université Paris-Saclay. One theory is that energetic activity might help food progress through the gastrointestinal tract. But: More exercise isn’t always better for gut health—the French study also found that regularly engaging in extremely intense or extended exercise regimens can increase intestinal wall permeability, potentially allowing pathogens to enter the bloodstream—a problem that’s sometimes called leaky gut. We all get a slightly leaky gut from time to time, such as when we are stressed, but once you take away the stressor, it resolves with little or no detriment. Leaky gut is likely to be an issue only for people who push their bodies through extremely challenging workouts, such as triathlon training, so this potential risk shouldn’t stop anyone from doing a standard exercise regime. But if you have a sensitive gut, stick to low- and moderate-intensity workouts.

Give your gut what it wants, and you can eat what you want. You might have heard that consuming red meat, heavily processed foods, sugary foods and fried foods are bad for the microbiome. That’s somewhat true…but consuming such foods is likely to cause significant gut issues only when you eat so much that you crowd out the beneficial foods the microbiome needs. If your diet is largely healthy and includes the wide range of plant-based foods cited above, then indulging in unhealthful foods such as red meat and sugary treats now and then is not likely to do very much harm—in fact, sugar, for example, is absorbed very high up your gut and therefore doesn’t actually come into contact with most of your gut microbes.

Chew food thoroughly. The foods you choose aren’t the only way that your eating habits affect your microbiome. Chewing food not only physically breaks it down, it also gives the food greater exposure to the digestive enzymes in saliva. Example: One study by researchers at Purdue University found that chewing nuts 40 times as opposed to just 10 times substantially increases the nutritional benefits. Not every food requires as much chewing to break down as nuts, of course, but it is worth taking the time to chew foods until they are very broken down, and that may take 20 to 30 chews.

It might be better to skip the late-night snack. Intermittent fasting—not eating for an extended time during the course of a day—has been linked to numerous health benefits, including weight loss and reduced inflammation. Even better: It might benefit gut health, in particular by giving the gut lining time to repair itself. You don’t have to skip meals to take advantage of the benefits of intermittent fasting—there is no evidence that extending these intermittent fasts beyond 12 hours is helpful. Best: Don’t eat between dinner in the evening and breakfast the next morning, and you’ve given your gut all the rest it needs.

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