Which source of dietary fiber works best?


By Amy Norton
health day reporter

THURSDAY, Aug. 4, 2022 (HealthDay News) — If your diet is low in fiber, you can do your gut good by adding more — regardless of the fiber source, according to new research.

Many people know that fiber is the nutrient that keeps you regular. But it is also a key player in the composition of the gut microbiota — the vast collection of bacteria and other microbes that reside in the digestive tract.

When gut bacteria break down fiber, they produce certain short-chain fatty acids that are the primary source of nutrition for colon cells. Research also suggests that fatty acids play a role in regulating such vital functions as metabolism and immune defenses.

But it hasn’t been clear whether one type of fiber supplement is better for gut bacteria than the other.

In the new study, researchers tested three common fiber powder supplements: inulin (an extract from chicory root), wheat dextrin (in this case, the Benefiber brand), and galactooligosaccharides (Bimuno).

They recruited 28 healthy adults and gave them each of the supplements to use for a week, with a week off between each product.

Overall, the study found that no supplement outperformed the others in altering the gut microbiome of consumers. Each supplement stimulated the production of butyrate – an important fatty acid that helps control inflammation.

If one study participant produced more butyrate after using a fiber supplement, they responded just as well to the other two, said Jeffrey Letourneau, a doctoral student at Duke University in Durham, North Carolina, who was part of the research team.

But while the fiber supplement didn’t matter, the person did: The supplements only accelerated butyrate production in participants who normally ate few high-fiber foods, the study found. .

This makes sense, according to Létourneau: it is the “low fiber consumers” who would make a substantial change by adding a daily fiber supplement.

But that term also describes most Americans, he pointed out.

Experts generally recommend that women aim for 25 grams of fiber per day, while men should aim for 38 grams. The average American adult, however, consumes only about 30% of these amounts.

And in the grand scheme of human history, Letourneau said, even the recommended amounts of fiber are likely well below what our ancestors felled. He pointed to research showing that members of the Hadza tribe in Tanzania still consume 100-150 grams of fiber per day, due to diets high in foods like berries, honey and tubers.

So the new research – published July 29 in the journal Microbiota — emphasizes the importance of getting more fiber from any source.

The study focused on supplements, in part because they’re easy to study, Letourneau said. The researchers gave each participant individual pre-measured doses of fiber supplements, so they only had to pour the powder into a drink once a day.

These doses amounted to 9 grams of wheat inulin or dextrin, or 3.6 grams of galactooligosaccharides, per day.

Dietary fiber would be preferable, however, according to a dietitian who was not involved in the study.

Plant foods not only provide various forms of fiber, but also a range of vitamins, minerals and beneficial “phytochemicals,” said Nancy Farrell Allen, spokesperson for the Academy of Nutrition and Dietetics and teacher at the of Rosalind Franklin University of Medicine and Science in North Chicago, Illinois.

“I believe food is the best way to meet fiber needs,” she said.

Farrell Allen mentioned a long list of fiber-rich foods, including a range of vegetables and fruits; bran cereals and whole grains like farro; “legumes” like lentils and chickpeas, and legumes like soybeans and peanuts.

She also had a caveat about fiber supplements: they can cause nasty gas, bloating and prolonged indigestion.

Letourneau agreed that whole foods have “real benefits” that can’t be captured in a supplement. But given how important fiber is — and how scarce it is in American diets — it’s good to eat more of it, as you can.

“My attitude is this: anything that you can integrate into your life, in a sustainable way, is good,” Letourneau said.

In more good news, it doesn’t take long for the added fiber to make a difference to your gut bacteria. In a separate study, Duke researchers found that fiber supplements began to alter people’s gut bacteria within a day, changing the composition and activity of the microbiome.

“Things seem to be changing very quickly,” Letourneau said.

The research was funded by the US National Institutes of Health and other government and foundation grants.

More information

Harvard University has more on fiber and health.

SOURCES: Jeffrey Letourneau, BS, doctoral student, molecular genetics and microbiology, Duke University, Durham, NC; Nancy Farrell Allen, MS, RDN, spokesperson, Academy of Nutrition and Dietetics, Chicago, and nutrition teacher, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois; MicrobiotaJuly 29, 2022, online; ISME JournalJuly 23, 2022



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