How Eating More Fiber Can Protect the Gut Microbiome

The Importance of Fiber

Eating more fiber, which is found in whole grains, vegetables, and fruits, might help protect against dangerous bacteria in the gut.

Fiber and Beneficial Bacteria

After analyzing samples from the gut microbiomes of more than 12,000 people hailing from 45 countries, researchers determined that people with high levels of a certain type of beneficial bacteria known as Faecalibacterium were more likely to have low levels of potentially fatal bacteria such as E. coli, according to the report published this month in Nature Microbiology.

Fiber Breakdown and Short-Chain Fatty Acids

The researchers also found that samples with high levels of Faecalibacterium had high levels of beneficial compounds called short-chain fatty acids, which are a byproduct from the breakdown of fiber. Research has indicated that having reduced levels of this type of bacteria is linked to inflammatory bowel or gastrointestinal conditions.

Diet and Gut Microbiome

“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,” the study’s principle investigator, Alexandre Almeida, a research fellow at Cambridge University, told NBC News in an email.

The Gut Microbiome

The gut microbiome is a collection of microbes including bacteria, fungi, and viruses that dwell in the gastrointestinal tract. Gut microbiomes vary from person to person.

High-Fiber Foods

The new findings suggest that eating high-fiber foods such as vegetables, beans, and grains might help protect against harmful bacteria, he added.

Limitations of the Study

Almeida cautioned that the new study doesn’t prove that fiber protects against harmful bacteria. “This was an observational study performed on the gut microbiome of people at one point in time, so we need to be mindful that most of our results are based on associations,” he said. “This means that future work is needed to experimentally test whether certain things like fiber and other nutrients prevent the incidence of infections in a longer time span.”

Analysis of Stool Samples

Using stool samples from 65 studies across 45 countries, the scientists analyzed the bacterial makeup from 12,238 people. They found that the composition of a person’s microbiome could predict whether the person’s gut was likely to be overrun with harmful bacteria.

Expert Insights

“This is an impressive analysis,” said Dr. Walter Willett, a professor of epidemiology and nutrition at the Harvard T.H. Chan School of Public Health and a professor of medicine at Harvard Medical School in Boston, who noted that it doesn’t prove that fiber affects a person’s susceptibility to harmful bacteria. “It’s one little piece of the puzzle. In the future it will be critical to include diet in the analysis.”

Fiber and Health

There are plenty of other reasons to consume the recommended amounts of fiber, Willett said. “There’s really solid evidence that fiber helps with diabetes, weight control, and cardiovascular disease.”

Recommended Daily Amount

Adults need 30 grams of fiber a day, Willett said.

Fiber Deficiency

Most Americans get only about 58% of that daily amount, according to U.S. Department of Agriculture research.

Eating a High-Fiber Diet

“But it’s not practical to count out the grams,” Willett said. “The simplest thing is to follow a couple of rules: Whenever you’re having grains, make sure they are whole grains, and eat a variety of fruits and vegetables. Just by doing that you’ll get plenty of fiber.”

Foods High in Fiber

Certain foods are especially high in fiber.

• 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)

Conclusion

Increasing fiber consumption can have numerous health benefits, including protecting the gut microbiome. While the study does not prove that fiber directly protects against harmful bacteria, it suggests that a high-fiber diet may be beneficial for overall health.

FAQs

Q: How much fiber do adults need per day?
A: Adults need 30 grams of fiber per day.

Q: What foods are high in fiber?
A: Certain foods are especially high in fiber, including unsweetened bran cereal, lima beans, pumpkin seeds, and raspberries.

Q: Can increasing fiber consumption protect the gut microbiome?
A: Yes, increasing fiber consumption may help protect the gut microbiome, although more research is needed to confirm this.

Q: How can I increase my fiber intake?
A: You can increase your fiber intake by eating a variety of fruits, vegetables, whole grains, and legumes, and by limiting your consumption of processed and refined foods.