Personalized fiber recommendation key for better gut health, reveals Cornell study

28 Jun 2024 --- Researchers at Cornell University have found that while nutritionists advise patients to increase their dietary fiber intake, its impact on health varies from person to person. The findings suggest that fiber recommendations should be personalized to consumers’ individual gut microbiome.

Published in the scientific journal Gut Microbes, the study focuses on resistant starch, a category of dietary fiber found in foods like bread, cereals, green bananas, whole-grain pasta, brown rice and potatoes.

The investigation found that different gut bacteria change according to different resistant starch types. Due to this, each person may have a unique response to eating a specific resistant starch, with some people deriving benefits while others may experience no effects. The determinant appears to be the diversity and composition of a person’s gut microbiome.

“Precision nutrition definitely has a use in determining what dietary fiber we should tell people to eat,” says Angela Poole, assistant professor of molecular nutrition and senior author of the study.

“This is critical because public messaging has advised people to eat more dietary fiber for decades. At the same time, less than 10% of people eat the recommended intake. Since there are many different types of dietary fiber and carbohydrates, a better strategy would be to collect data on each person and tell them which dietary fiber they can eat to get the most bang for their buck.”

Gut bacteria changes
Resistant starches come in five types. For the study, the researchers created three types of crackers: one with resistant starch type 2, occurring naturally, another with human-made starch resistant type 4, and a third control cracker similar to white bread. The 59 participants were asked to consume all three kinds of crackers for seven weeks, with their gut bacteria and fatty acid levels being monitored throughout the study.

Findings revealed that for participants who consumed resistant starch type 2 and 4, the abundance of various gut bacteria changed, in addition to recorded spikes and dips in fatty acid, based on the individual. The control cracker — which the researchers did not expect to contribute to producing short-chain fatty acids — had the highest increase.

Poole says that this significant takeaway could mean that eating white bread occasionally might be better than eating whole grain all the time. However, more research is needed to confirm whether and how this varies between people.

The President’s Council of Cornell Women and the National Institutes of Health supported the study.

In recent dietary fiber research, scientists from DTU National Food Institute and the Department of Nutrition, Exercise and Sports at the University of Copenhagen, Denmark, discovered that different types of bacteria in the colon compete to use tryptophan, an essential amino acid and that dietary fibers determine the outcome in favor of good health.