Could adding prebiotics to snacks improve gut health?

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A new study investigates adding prebiotics to snacks to boost gut health. lacaosa/Getty Images
  • Dietary fiber may help prevent cardiovascular disease, type 2 diabetes, and obesity through its effects on the gut microbiota, which is the community of microorganisms that live in the gut.
  • However, typical Western diets lack the fiber that these friendly microbes need to thrive.
  • Experiments in mice and humans suggest that snack foods supplemented with particular types of fiber can alter the gut microbiota and lead to widespread physiological effects.
  • It would be possible to source the fiber for future prebiotic snacks from food industry waste, such as peels, rinds, and husks, which manufacturers would otherwise discard.

The bacteria, archaebacteria, viruses, and fungi that live in the human gut — collectively known as the gut microbiota — have a profound effect on both physical and mental well-being.

Research suggests that by feeding the beneficial members of this community, dietary plant fibers can help stave off chronic health conditions, such as cardiovascular disease, type 2 diabetes, and obesity.

However, Western-style diets are often high in fat and deficient in these plant fibers.

The idea of supplementing otherwise unhealthy snacks, such as cookies and chips, with fiber might seem straightforward, but the relationship between diet, the microbiota, and individual health is highly complex.

Scientists at the Center for Gut Microbiome and Nutrition Research at Washington University School of Medicine in St Louis, MO, are investigating this relationship with a view to developing prebiotic snack products.

In previous work, they identified sources of fiber that are not only cheap and readily available — such as typically discarded peels, rinds, and husks — but also boost the gut microbes that adults with obesity tend to lack.

In their new research, which appears in Nature, they tested how snacks supplemented with some of these fibers affected the gut microbiota of mice and humans, looking at their possible physiological effects.

“Since snacks are a popular part of Western diets, we are working to help develop a new generation of snack food formulations that people will like to eat and that will support a healthy gut microbiome that affects many aspects of wellness,” says senior author Prof. Jeffrey I. Gordon, M.D., who directs the Edison Family Center for Genome Sciences & Systems Biology at Washington University School of Medicine.

The snack food manufacturer Mondelēz International, which owns brands such as belVita, Cadbury, and Oreo, partly funded the work.

In the first phase of their research, the scientists used “gnotobiotic” mice, which are raised in sterile conditions so that they lack any gut microbes of their own.

They colonized the guts of these mice with microbes from people with obesity, then fed the animals the type of high fat, low fiber diet that is associated with overweight and obesity.

Next, they consecutively introduced snacks to the mice’s diet that were supplemented with pea fiber, orange fiber, or barley bran. Between each type of snack were washout periods during which the mice only ate the high fat, low fiber diet.

This approach allowed the researchers to track the effects of each fiber type on the gene pool of the animals’ gut microbiota, which they did through analyses of microbial DNA in fecal samples.

They discovered that each snack led to an increased abundance of the genes necessary to make enzymes for digesting that particular fiber. Presumably, this was because the fiber gave bacteria with the right genes a competitive edge over the others.

In the second phase of the research, the researchers carried out similar experiments involving 12 human volunteers who were overweight or had obesity.

To avoid any changes arising from differences in their diets, the volunteers ate a strictly controlled diet that was high in saturated fat and low in fiber.

The researchers then monitored genetic changes in their microbiota before, during, and after a 2-week period, during which they also ate snack bars supplemented with pea fiber.

The team observed similar changes in the volunteers’ gut microbiota to those that they had seen in the mice, with an increased abundance of the genes needed to digest this fiber.

Finally, the scientists investigated whether eating snacks containing several different types of fiber would lead to more significant changes in the microbiota than eating pea fiber alone.

A group of 14 volunteers first ate a snack containing a combination of two fibers: pea fiber and inulin, which occurs naturally in onions, bananas, asparagus, artichokes, and chicory root. Later, after a washout period, they ate a snack containing four fibers: inulin, pea fiber, orange fiber, and barley bran.

This part of the study showed that the more types of fiber in the diet, the greater the abundance of bacterial genes that play a role in fiber metabolism.

These genetic changes were closely correlated with changes in the levels of proteins in the blood that contribute to a wide range of key physiological processes.

For example, there were significant changes in the levels of proteins involved in glucose metabolism, immunity, blood coagulation, blood vessel function, and the biology of bone and nerve cells.

Overall, the experiments reveal how responsive the gut microbiota is to changes in dietary fiber, even in individuals who are accustomed to eating a low fiber diet.

“In principle, the fibers can be incorporated into a variety of snack formats familiar to consumers — chips, bars, biscuits, etc.,” Prof. Gordon told Medical News Today.

One of the limitations of the study was that the volunteers ate a tightly controlled diet in addition to the fiber-supplemented snacks. In the real world, diets are much more complicated.

However, the researchers are already exploring whether their preliminary findings hold up when people can eat what they like.

“Follow-on studies involve administering the snack food prototypes to participants who are consuming their normal diets,” said Prof. Gordon.

“This approach can provide insights about the robustness of the effects, and dose dependency, of fiber snack formulations on the gut microbiome and host physiology under more realistic consumer settings,” he added.

The study identified protein biomarkers of possible physiological changes in participants’ blood. However, it is currently unknown whether such changes would reflect genuine health benefits.

Only clinical trials can reveal whether such snacks might help prevent type 2 diabetes or obesity, for example.

In an accompanying article, Avner Leshem and Eran Elinav from the Weizmann Institute of Science in Rehovot, Israel, conclude:

“[These] findings provide valuable mechanistic insights into the microbial contributions to human dietary responses. This will probably lead to long-term, randomized clinical trials that assess causal links between distinct food ingredients, microbiome modulation, and downstream health-related outcomes for humans.”

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