Legumes: The Gut-Boosting, Heart-Healthy Superfood

Legumes — such as beans, lentils, and peas — are packed with nutrients that are beneficial for the body. Not only are they loaded with complex carbohydrates, fiber, minerals, and vitamins, they’re also a rich source of protein — minus the saturated fat and cholesterol common in many animal proteins.

The American Heart Association recommends beans and other legumes as part of a healthy eating plan.

Studies even say that a legume-heavy diet may reduce cholesterol,

lower blood pressure,

and improve diabetes risk.

When it comes to the gut, fiber-rich legumes overall promote regular bowel movements and encourage beneficial gut bacteria for a healthy digestive tract. But digesting beans can be difficult for some, leading to discomfort, such as bloating, gas, and other intestinal problems.

The Favorable Force of Fiber

“Legumes are super healthy,” says Christopher Damman, MD, a clinical associate professor of medicine in the division of gastroenterology at the University of Washington in Seattle. “They’re one of the plant-based foods that are most associated with good health in epidemiological studies, so people who consume more beans tend to have better health outcomes.”

One of the biggest benefits of legumes is the fiber they provide, and most Americans aren’t getting enough of that nutrient. The American Society for Nutrition estimates that only 5 percent of men and 9 percent of women are getting the recommended daily amount of dietary fiber.

Health guidelines recommend 14 grams (g) of fiber for every 1,000 calories consumed daily. To get the proper amount, the typical woman should aim for about 25 g (for a 2,000 calorie diet), while men should aim for 38 g (for a 2,500 calorie diet).

Note that we need slightly less fiber as we age. After age 50, adequate intake drops to 30 g for men and 21 g for women, per the National Resource Center on Nutrition and Aging.

There are two types of dietary fiber — soluble and insoluble. Each type helps the body, and legumes offer both.

“Soluble fibers hold water, which helps to add weight to the stool, making it easier to pass,” says Desiree Nielsen, RD, a registered dietitian based in Vancouver, British Columbia. “Insoluble fibers help to sweep the gut clear, promoting regularity as well as proper turnover of the gut cells.”

In addition, soluble fiber binds to cholesterol in the intestine and removes it from the body through our stool. The National Lipid Association notes that 5 to 10 g of soluble fiber a day can lower total and LDL-cholesterol (bad cholesterol) by 5 to 11 points, and sometimes more.

Research has shown that high fiber foods contain beneficial nutrients that metabolize into compounds such as nitric oxide, which may improve blood pressure. They also contain antioxidants (compounds that reduce oxidative stress). Oxidative stress is a major risk factor for the development and progression of atherosclerosis (a buildup of plaque in the arteries).

Fiber slows the absorption of sugar, improving blood sugar levels and lowering diabetes risk, according to Mayo Clinic.

Also, because they are usually more filling than low-fiber foods, legumes can satisfy hunger for longer periods, and help you eat less during the day, which can help with weight loss.

Fuel for the Gut Microbiome

Fiber from legumes provides an excellent source of energy for our gut microbiome (the trillions of microorganisms that live in our gut). Dietary fiber is fermented by bacteria in the colon to produce short-chain fatty acids.

“Short-chain fatty acids are used as fuel for our colon cells, as well as our liver and muscle tissues,” says Brogan Taylor, RD, a registered dietitian with Banner Health in Phoenix, Arizona. “Feeding the beneficial gut bacteria ensures that our microbiome stays healthy and that we don’t have overgrowth of harmful forms of bacteria.”

Dr. Damman, who edits a blog called Gut Bites MD, stresses that Americans often have diets that are low in plant-based foods and fiber in particular. A diet void of legumes may starve gut microbes, making for an unhealthy microbiome.

A 2023 study found that people with colon cancer who incorporated beans into their diet increased the diversity of their beneficial gut bacteria while warding off harmful bacteria. A coauthor of this research, Carrie Daniel-MacDougall, PhD, an associate professor of epidemiology with the University of Texas MD Anderson Cancer Center in Houston, said in a press release that flourishing bacteria in the colon may support immune health and regulate inflammation.

“Another interesting item to note is that magnesium has generated some attention lately for its benefits on mental health and stress, sleep, and gut health,” says Taylor. “Black beans, edamame, and lima beans are great dietary sources of magnesium.”

Beans, lentils, chickpeas, peas, and soybeans are also great sources of iron (which is especially important for vegetarians) and phosphorus (which is needed for growth, maintenance, and repair of all tissues and cells). While these are all essential minerals, some studies suggest that iron and phosphorus in excessive amounts may be toxic to the body.

The National Institutes of Health provides guidelines broken down according to age and sex detailing recommended levels of both iron and phosphorus to maintain optimal health without going overboard.

Legumes May Be Challenging for Those With IBD or IBS

While most people can tolerate beans, those with digestive conditions such as Crohn’s disease or ulcerative colitis, for example, may have gastric distress because short-chain carbohydrates may not be absorbed properly in the gut.

People with irritable bowel syndrome (IBS) or inflammatory bowel disease (IBD) have been known to have discomfort after eating legumes, but experiences can vary greatly from one individual to the next.

“One person’s IBS might be very different from somebody else’s, so if you have issues that you think are food related, talk with a health professional — a gastroenterologist or nutritionist — to sort out the cause,” says Damman.

He further explains that gradually introducing legumes into a diet may prevent gastric turmoil. “It may be that key microbes in your gut are underrepresented,” he speculates. “If you take some time to introduce high fiber foods into your microbiome, it may recalibrate. A trained medical professional can help you determine whether your gut is just out of practice or whether you really can’t tolerate certain foods.”

Lectin and Other Potential Gut-Trouble Causes

For some people, sugars in legumes called raffinose family oligosaccharides (RFOs) make eating these foods unpleasant because these sugars can fuel flatulence. Authors of a study on RFOs wrote that flatulence is “the single most important factor that deters consumption of legumes.”

On the other hand, RFOs have beneficial effects in the large intestine and may promote the growth of beneficial bacteria.

Some dietitians caution against consuming too much lectin. Lectins are carbohydrate-binding proteins present in legumes that can prevent the absorption of certain nutrients into the body. In high amounts, they may decrease absorption of various nutrients, although this has not been demonstrated in resource-rich populations.

Nielsen believes there is a great deal of misunderstanding surrounding lectins.

“While it is true that certain lectins, such as phytohaemagglutinin in kidney beans, can be toxic in large amounts, it is incorrect to say that all lectins are harmful,” she says. “What’s more, soaking and cooking legumes greatly reduces lectin compounds. And in fact, eating a diet high in fiber is thought to protect gut barrier function.”

In Nielsen’s estimation, soaking and cooking kidney beans will take lectins down from as many as 70,000 units to less than 500.

How to Get More Legumes in Your Diet

For Taylor, there really aren’t any legumes that are better than others: “It is hard to say that one or another legume has the most benefits. In general, they will all be rich in protein, fiber, B vitamins, iron, folate, calcium, magnesium, and zinc.”

Nielsen agrees but points out that brightly colored legumes such as red kidney beans and black beans contain plant pigments that may provide extra antioxidant and anti-inflammatory properties.

So with the overall pluses of legumes outweighing the minuses, here are some suggestions from our experts on how to get more legumes into your diet.

Add legumes to salads, soups, or stews. “The great thing about legumes is that you can add them to almost any meal without changing flavor too much,” notes Taylor.
Consider the versatility of the chickpea. Chickpeas (or garbanzo beans) can come in many forms. Taylor recommends trying hummus (a puree of chickpeas with tahini, garlic, and citrus) as a replacement for mayonnaise on a sandwich. She also suggests baking them for a crunchy snack.
Be creative when making black beans. Black beans can be prepared in a variety of ways — in Mexican food like burritos and tacos, for dips, or in a black bean burger.
Choose lentils for a fast legume meal. Cooking beans from their dry form can be time-consuming. Some beans can take as long as two hours to cook — even when you soak them overnight. “Lentils are wonderful because they are quick to cook without soaking,” says Nielsen. Split red lentils can cook in as little as 5 minutes, while whole lentils may take 15 to 20 minutes. Check out our lentil recipe below.
Snack on edamame. Edamame are light green soybeans in a pod that have grown in popularity in the United States. But edamame has been around for more than a millennium as a staple in many Asian diets. Packed with protein, it’s also considered a good source of omega-3 fatty acids. Taylor says that several of her patients enjoy them steamed with everything-bagel seasoning.
Eat more tofu. This soybean product is often used as a meat substitute because it is high in protein and other nutrients. In fact, the American Heart Association says it’s much better for the heart than animal protein. Soybeans are also used in soy milk, which is considered a good source of fiber.
Don’t forget the peanut. Peanuts are actually a legume and not a nut. Grown underground, peanuts make great snacks, toppings on salads and entrees, and are super popular when converted into peanut butter. In addition to providing fiber, peanuts are full of heart-healthy monosaturated fat, vitamin E, multiple minerals, and contain zero cholesterol.

“In the big picture, most people should be eating more legumes if they can,” says Damman. “One other bonus — they’re easy on the pocketbook.”

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