• Posted January 22, 2025

High-Fiber Diets Linked to Gut Health & Fewer Harmful Bacteria

Could eating more fiber be the key to a healthier gut? Research suggests the answer is yes.

The findings, published recently in the journal Nature Microbiology, analyzed gut microbiomes from more than 12,000 people in 45 countries. It found that individuals with higher levels of beneficial gut bacterium called Faecalibacterium also had fewer harmful bacteria such as E.coli. 

“The main takeaway from our study is that our gut microbiome plays an important role in reducing the growth of potentially harmful bacteria in our gut, and it seems this effect may be modulated through diet,” lead researcher Alexandre Almeida, a fellow at Cambridge University, told NBC News. 

Faecalibacterium thrives on fiber-rich foods like vegetables, beans and whole grains. It produces short-chain fatty acids, compounds known to benefit gut health.

Research has linked lower levels of these bacteria to gastrointestinal conditions like inflammatory bowel disease (IBD).

While the study doesn’t prove that eating more fiber directly reduces harmful bacteria, increasing fiber intake offers many health benefits, Almeida said.

“There’s really solid evidence that fiber helps with diabetes, weight control and cardiovascular disease," Dr. Walter Willett, a professor at Harvard T.H. Chan School of Public Health and at Harvard Medical School in Boston, said in a news release.

Adults need about 30 grams of fiber daily, according to Willett, but most Americans consume about 58% of that amount.

Some high-fiber food swaps

• Unsweetened bran cereal (14 g per ½ cup) versus toasted oat cereal (3 g per cup)

• Lima beans (13.2 g per cup) versus asparagus (2.9 g per cup)

• Pumpkin seeds (5.2 g per ounce) versus hazelnuts (2.8 g per ounce)

• Raspberries (8 g per cup) versus blueberries (3.6 g per cup)

“I see people with gastrointestinal conditions like constipation and diarrhea, and fiber is the only thing that is good for both,” New York gastroenterologist Dr. Daniel Freedberg said in a news release. He's an associate professor of medicine and epidemiology at the Columbia University Vagelos College of Physicians and Surgeons in New York City.

He noted that a high-fiber diet might protect the colon.

“There are some studies where people were briefly randomized to consume a very, very high-fiber diet or an ultraprocessed diet,” Freedberg said. “In their biopsies, you can see not-so-good changes in the colon tissues of people who consumed the ultraprocessed food.”

More information

The Mayo Clinic has more on high-fiber diets.

SOURCE: NBC News