Nutritionists generally advise everyone to eat more dietary fiber, but a new Cornell University study suggests that its effects on health can vary from person to person. The findings indicate that recommendations should be tailored to each individual's gut microbiome.

The study, published in Gut Microbes, focused on resistant starch, a category of dietary fiber found in such foods as bread, cereals, green bananas, whole-grain pasta, brown rice and potatoes.

The researchers identified the gut microbe species that change in response to two different types of resistant starch. They found evidence that each individual may have a unique response to eating a resistant starch, with some people benefiting and others experiencing little or no effect. The reason appears tied to the level of 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," said Angela Poole, assistant professor of molecular nutrition and senior author of the study.

"This is critical because we've had public messaging advising people to eat more dietary fiber for decades," Poole said. "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."

In the study, Poole and colleagues tested three dietary treatments on 59 participants over seven weeks.