Cutting carbs? You might be killing off some of your good gut bacteria. Find out why, then discover the best carbohydrate foods to eat more of to maximize your microbiome.
Reviewed by Dietitian Jessica Ball, M.S., RD
Whether you call it Atkins, Keto or simply aim to live la vida low-carb, these diets continue to be among the most trendy eating patterns in America.
Depending on which plan you follow, low-carb dieting entails restricting carbohydrate consumption to anywhere from 20 to 130 grams per day. For reference, two Medjool dates have 36 grams and one 5-inch sweet potato has 26 grams. Not taking into account any other bite you consume that day, noshing on either of those nutrition all-stars could already push you over your low-carb limit if you’re following a very low-carb plan, such as the keto diet.
Pictured Recipe: Gochujang-Glazed Tempeh & Brown Rice Bowls
While low-carb eating may lead to quick weight loss, the rigidity of the plan makes it nearly impossible to stick with. (No wonder keto was ranked among the worst diets of 2023.) Beyond that, research suggests that super-low-carb strategies probably aren’t doing other aspects of your body any favors, including your heart and your ever-important gut.
“Carbs have gotten a bad reputation, which to be honest, annoys me. It’s extremely important that we separate good carbs from bad carbs,” says Will Bulsiewicz, M.D., a Charleston, South Carolina-based gastroenterologist and the author of The Fiber Fueled Cookbook.
And it’s extremely important that we eat them, confirms Kenneth Brown, M.D., a gastroenterologist in Plano, Texas and the host of the Gut Check Project podcast. All three macronutrients—carbohydrates, fats and proteins—are important for our bodies and are the basic building blocks of our food and energy to fuel our body. The healthiest eating pattern includes a balance of all three, according to Bulsiewicz.
According to an August 2018 study published in The Lancet Public Health, humans who live the longest tend to score about 50 to 55% of their total daily caloric intake from carbohydrates.
Not only are carbs our body and brain’s preferred source of energy, but they also play a vital role in our gut health. (ICYMI, a healthy population of good bacteria, AKA microbiome, in our GI tract has been linked to lower risk for everything from depression and anxiety to certain cancers to heart disease.) One particular type of carb, fiber, is especially impactful in terms of our gut health…or lack thereof.
“Research suggests that about 95% of Americans are inadequate in their fiber and resistant starch consumption. These are both complex carbohydrates, and this is causing damage to our gut microbiome,” Dr. Bulsiewicz says, siting a 2017 study published in the American Journal of Lifestyle Medicine. “So please, I beg you. Can we stop trashing ‘carbs’ as a category?”
Instead, Dr. Bulsiewicz and Dr. Brown agree that your goal should be to focus on fueling up with more of the right carbs that will feed your microbiome, muscles, brain and taste buds all at once.
Related:10 Healthiest Carbs You Should Be Eating, according to a Dietitian
What to Look For in the Best Carbs for Gut Health
A review published March 2020 in the journal Microorganisms confirms that carbohydrates play a large role in the short-term and long-term health of our gut microbiome overall. That being said, carbohydrates can positively and negatively impact gut health, depending on which types of carbs you eat, Dr. Brown explains.
“Eating a lot of refined carbs—such as those found in sugary drinks and processed foods—can lead to inflammation and an imbalance of gut bacteria, which may increase the risk of various digestive disorders,” he says. “On the other hand, consuming fiber-rich carbohydrates—such as those found in whole grains, fruits and vegetables—can help promote gut health by nourishing beneficial gut bacteria, regulating bowel movements and reducing inflammation.”
To optimize gut health, it’s best to consume a variety of high-fiber carbs and limit intake of refined carbs or foods high in added sugar. The level of refinement with carbohydrates is critically important, Dr. Bulsiewicz adds. Refined carbohydrates like white bread, pastries and sugar-sweetened drinks have much of their natural fiber and nutrients removed, which can trigger rapid spikes in blood sugar and may contribute to insulin resistance and other metabolic issues. Unprocessed or minimally-processed whole plant foods, however, retain their natural fiber and nutrient content, and provide more benefits for gut health than ultra-processed items.
“The choice is rather simple. Whenever possible, opt for the food that you could grow instead of the food developed in a lab,” Dr. Bulsiewicz says. “Anytime we add more whole plant foods to our plate we are fueling our body and our microbiome with premium fuel.”
Related:12 Foods to Improve Your Gut Health Overnight
The Best Carbs for Gut Health, According to Gastroenterologists
Produce items are technically carbs, true. These always get a thumbs up from Dr. Bulsiewicz and Dr. Brown, so consider any of your favorite fruits and veggies also part of this list. But since we’ve already covered the best fruit for gut health and best vegetables for gut health, we’re focusing on more classic carb sources here.
“Whole grains, such as oats, quinoa, brown rice and whole wheat bread, are high in fiber, vitamins and minerals, making them a smart choice for promoting gut health and reducing the risk of chronic diseases,” Dr. Brown says.
While any whole grain is great for your gut, oats stand out from the pack, according to an October 2021 review in The Journal of Nutrition. After reviewing 84 studies, oat intake was correlated with an increase in beneficial gut bacteria among those without any digestive disorder and individuals with celiac disease.
Oats offer a special kind of soluble fiber called beta-glucan that turns into a gel-like consistency in the gut and helps to keep things moving through your digestive tract, bulk up your stool and help you poop more regularly.
Any kind of fermented plant food is a favorite of Dr. Bulsiewicz—and your microbiome. Sauerkraut, kimchi, pickles, olives and tempeh “have the fiber and polyphenols to support a healthy gut microbiome, and also deliver living microbes [probiotics] that provide added benefits. My goal is to get 3 to 5 servings of fermented food on a daily basis,” he says.
Tempeh, which is made from fermented soybeans that are pressed into loaf-like forms, is a particularly wise choice. Beyond offering a nice mix of protein, fat and carbs, tempeh offers an uncommon one-two punch of both prebiotics and probiotics; two key players in boosting your gut microbiome. After just 28 days of consuming 3 ½ ounces of cooked tempeh per day, participants in a February 2019 Food Research study experienced significant improvements in their overall gut health profile.
Related:The Best Fermented Foods For Your Brain, According to New Research
3. Chia, Flax and Hemp Seeds
Versatile, easy to sneak into everything from smoothies to salads and nutrition all-stars all at once, this trio of omega-3 super seeds are also mainstays in Dr. Bulsiewicz’s diet.
“I’m a huge fan of chia, flax and hemp seeds. Each of them is high in fiber, omega 3 fats and protein. In other words, you are elevating all three macros in your diet when you enjoy these foods,” Dr. Bulsiewicz says.
Beyond the gut-supporting fiber, the omega-3s in these seeds have been proven to produce anti-inflammatory short-chain fatty acids that may help strengthen our intestinal walls and bolster immunity, according to a December 2017 study in the International Journal of Molecular Sciences. That same study also validates that omega-3s, like those found in seeds, can have a positive influence on the gut-brain axis; the conversation going on between our microbiomes and our brain.
Loaded with fiber and resistant starches to help fuel a healthy gut microbiome, beans and legumes “are among the healthiest foods out there,” Dr. Bulsiewicz says. Bonus: They’re budget-friendly. “With inflation being what it is, it’s nice to have a food option that’s inexpensive and wildly healthy.”
Beans and legumes like chickpeas, black beans, kidney beans and lentils are a potent source of plant-based protein as well, Dr. Brown validates, which can help regulate blood sugar levels (among other important things).
“Studies show that eating legumes may help reduce your risk of chronic diseases like heart disease and diabetes. They also promote regular bowel movements, help you feel fuller for longer and support good gut bacteria,” Dr. Brown says.
A November 2017 review in the International Journal of Molecular Sciences found that small-but-mighty lentils deliver polyphenols and prebiotic carbs that feed our good gut bacteria in such a way that can help reduce the risk for gut-related diseases.
The Bottom Line
Stop steering clear of carbs. A balanced, high-fiber diet (yep, fiber is a type of carb!) can help support optimal gut health and reduce your risk for chronic diseases, Dr. Brown summarizes. The best carbs for gut health include fruits, vegetables, whole grains, seeds, beans, legumes and fermented plant foods.
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