- The researchers previously identified a link between fiber intake and positive health outcomes.
- The fibers promote a healthy intestinal microbiome, as the bacteria metabolize them.
- A recent study found that a 2-week increase in fiber intake significantly altered the intestinal microbiome.
The researchers found that a 2-week increase in fiber intake can significantly alter a person’s intestinal microbiome, including an increase in species of bacteria that break the fiber.
However, the amount of short-chain fatty acids (SCFAs) has not increased. SCFAs are the result of the breakdown of fibers by bacteria and perform various functions in the body.
For example, SCFAs are used as a
The research, which appears in the newspaper mSystems, establishes the basis for future studies to explore in more detail the relationship between fiber intake, intestinal bacteria and SCFAs.
Fiber plays an important role in human health. For example, a recent review of several meta-analyzes found that people who eat more fiber significantly reduce their chances of dying from a cardiovascular event.
However, only 1 in 20 people in the United States consumes the recommended amount of fiber.
According to Dr. Katrine Whiteson, associate professor of molecular biology and biochemistry, co-director of the Microbiome Initiative at the University of California, Irvine (UCI) and co-author of this study:
“The lack of fiber intake in the industrialized world is killing our intestinal microbes, with important health consequences that can be associated with increases in colorectal cancer, autoimmune diseases and even decreased vaccine effectiveness and response to cancer immunotherapy.
The small intestine cannot digest fiber. Instead, according to the authors of the present study, it passes into the colon, where microbes are able to break down the fiber.
This process results in the production of SCFAs. Experts believe that they are important for a number of factors that affect a person’s health.
The authors of the present study wanted to study the relationship between a short-term increase in dietary fiber, the composition of the intestinal microbiome and the presence of SCFAs.
To investigate, the researchers conducted a study involving 26 undergraduate students enrolled in a UCI biology course, in addition to their instructors.
At week 1, participants ate their normal diet and provided three stool samples for analysis.
In week 2, participants started a high fiber diet. They monitored their nutritional intake through a fitness app, with the goal of consuming 40 grams (g) of fiber per day. To help, the researchers provided them with 10 high-fiber meals a week from a variety of different plants.
In the third week, participants were encouraged to increase their fiber intake to 50 g per day. During this week, participants provided three more stool samples.
According to graduate student Andrew Oliver, a teaching assistant in the course, “students increased their fiber intake by an average of 25 g per day, but the variability in pre-intervention fiber intake was substantial.”
“Some students needed to go from almost zero to 50 g per day until the end of the study. We were all a little obsessed with the amount of fiber in the food we ate. “
The researchers then analyzed the samples using DNA sequencing to identify the composition of the bacteria. They used gas chromatography to measure SCFAs.
The researchers found that the composition of the participants’ intestinal microbiomes changed by about 8% after the dietary intervention.
This was largely due to the increase in bacteria known to break the fiber, including Bifidobacterium, Bacteroides, and Prevotella.
However, the researchers saw no statistically significant increase in SCFAs. They speculate that this may be because stool samples do not accurately represent the levels of SCFAs in the intestine, which are found mainly in the cell walls of the intestines.
The researchers also suggest that the 2-week intervention may not have been long enough to see any difference in SCFAs.
According to Dr. Whiteson, “we hope to carry out dietary fiber interventions for longer and study how fiber can support the intestinal microbiome and promote health.”
“Right now during a pandemic, when we need our immune health and healthy responses to the vaccine, we encourage everyone to think about the diversity of plants in their diets and add some beans, berries and avocados where they can.”