Study shows how high fiber intake can alter gut microbiome

Eating a nutrient-dense diet can help us stay healthy.

Americans don’t eat enough fiber and it’s been shown to have a link to diseases such as Type 2 diabetes and colon cancer. reported that just 5% of people in the U.S. eat the Institute of Medicine recommended daily fiber intake, which is 25 grams for women and 38 grams for men.

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A recent study has also found that consuming high amounts of fiber can alter the gut microbiome, the bacteria of which can metabolize fiber into byproducts that are critical for human health.

The research, which was announced in a March press release, was published by the American Society for Microbiology.

Research from a team led by University of California Irvine Microbiome Initiative co-directors Katrine Whiteson and Jennifer Martiny as well as Julia Massimelli Sewall has demonstrated that a higher intake of fiber for two weeks noticeably changed the gut microbiome.

Whiteson, Martiny and Sewall are all professors at UCI.

“The lack of fiber intake in the industrialized world is starving our gut microbes, with important health consequences that may be associated with increases in colorectal cancer, auto-immune diseases and even decreased vaccine efficacy and response to cancer immunotherapy,” Whiteson, an associate professor of molecular biology and biochemistry, said in a statement.

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In a UCI undergraduate biology course, the team conducted a two-week dietary intervention. Each week, participating students were given 10 high-fiber unprocessed meals. They gathered samples to trace the composition of their gut microbiome before and after the intervention. Additionally, students recorded their macronutrients to reach 50 grams/day during the two-week intervention period, which was the goal.

“The students came to class very excited to discuss what they had eaten and could not wait to analyze the microbiome sequencing information to make data-driven conclusions. The study had an interesting and educational impact,” Sewall, an assistant teaching professor of molecular biology and biochemistry and course instructor, said in a statement. “Our education research showed that the experience increased student’s interest in science and heightened the awareness of their diet habits.”

According to graduate student Andrew Oliver, a course teaching assistant who coached students during the study and encouraged them to drink plenty of water, students’ daily fiber intake was 25 grams on average. Still, he added, “the variability of pre-intervention fiber intake was substantial.”

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“A few students had to go from nearly zero to 50 grams daily by the end of the study,” Oliver, who also provided instruction in microbiology methods and analysis, said. “We all became a little obsessed with how much fiber was in the food we were eating.”

After comparing the overall bacterial composition and conducting additional experiments, researchers discovered the two-week intervention noticeably changed the structure of the individual gut microbiome. That included an increase in the abundance of probiotics that normally live in the stomach and intestines. A significant shift in the abundance of fatty acids was not detected, however.

“We hope to carry out longer dietary fiber interventions and study how fiber can support the gut microbiome and promote health. At this time during a pandemic, when we need our immune health and healthy vaccine responses, we encourage everyone to think about the plant diversity of their diets and add some beans, berries and avocados where they can,” Whiteson said.

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