The science supporting the benefits of maintaining digestive health is emerging. As researchers delve deeper into the positive effects of fiber, probiotics, prebiotics and inulin, they are discovering associations with gut health, immune system health and weight management.

To the average consumer, the evolution of nutrition science may seem somewhat surprising, said Phil Lempert, the chief executive officer of Supermarketguru.com and The Lempert Report. Speaking at the International Dairy Foods Association’s Dairy Forum in Palm Desert, Calif., this past month, Mr. Lempert noted that the food and beverage industry has not effectively communicated that nutrition science is evolving.

“We have not done a good job communicating to consumers that as we learn more about nutrition science things might change,” he said.

In the case of digestive health’s role in maintaining a healthy lifestyle, many of the changes are positive, and consumers are paying attention.

In its Functional Foods Consumer Survey, published this past October, the International Food Information Council found that digestive health is a top-of-mind topic when consumers think about functional foods. Ten per cent of survey respondents said digestive health was the most common benefit associated with functional foods. Only two other answers, “provides specific nutrient/food component” (28%) and “cardiovascular health” (13%) rated higher.

Unfortunately, the IFIC survey also said consumers overestimate the amount of fiber they may be getting in their daily diet. The survey painted a stark picture of how much fiber consumers believe they are consuming vs. how much they are actually consuming. Of the consumers surveyed, 67% perceived they were meeting their dietary needs for fiber while approximately 5% were actually meeting their needs for dietary fiber. IFIC reached the conclusion by comparing the answers given by survey respondents to 2010 NHANES data.

Figuring out how fiber works

While there is ample evidence about the benefits of fiber in digestive health, researchers are working to identify how it is metabolized by the body. Research at the University of York’s Structural Biology Laboratory in the United Kingdom has begun to uncover how gut bacteria metabolize the complex dietary carbohydrates found in fruits and vegetables, for example.

Microbiota plays a role in human health and is central to the human metabolism. A research team at the University of York has identified how one group of gut bacteria, known as bacteroidetes, which are anaerobic bacteria, that digest complex sugars known as xyloglucans. The xyloglucans make up to 25% of the dry weight of dietary fruit and vegetables, including lettuce, onion and tomatoes. Understanding how the bacteria digest complex carbohydrates informs studies on a range of nutritional issues, including research on prebiotics and probiotics, according to the researchers.

At the university’s Structural Biology Laboratory, the researchers have conducted studies into the precise functioning of specific enzymes. The work has shed further light on which organisms can and cannot digest certain fruits and vegetables, and how and why the “good bacteria” in the human gut perform in a specific fashion.

“Despite our omnivorous diet, humans aren’t well equipped to eat complex plant matter; for this we rely on our gut bacteria,” said Gideon Davies, a professor at the University of York who led the research. “This work is helping us to understand the science of that process.”

The University of York’s research was published on-line in the research journal Nature on Jan. 19.

The increasing power of probiotics

Another study underscores the potential benefits of probiotics and overall gut health in weight management. At the University of Laval, Quebec City, a study published in the British Journal of Nutrition showed certain strains of probiotics may help in weight loss and keeping the weight off.

Studies have shown the intestinal flora of obese people differs from that of people who are not obese. The difference may be due to the fact that a diet high in fat and low in fiber promotes certain bacteria at the expense of others. Professor Angelo Tremblay from the University of Laval and his team tried to determine if the consumption of probiotics may help reset the balance of the intestinal microbiota in favor of bacteria that promote a healthy weight.

To test the hypothesis, the researchers recruited 125 overweight men and women. The subjects underwent a 12-week weight-loss diet, followed by a 12-week period aimed at maintaining body weight. Throughout the study, half the participants swallowed two pills daily containing probiotics from the Lactobacillus rhamnosus family, while the other half received a placebo.

After the 12-week diet period, researchers observed an average weight loss of 9.7 lbs in women in the probiotic group and 5.7 lbs in the placebo group.

No differences in weight loss were observed among males in the two groups.

“We don’t know why the probiotics didn’t have any effect on men,” Dr. Tremblay said. “It may be a question of dosage, or the study period may have been too short.”

After the 12-week maintenance period, the weight of the women in the placebo group remained stable but the probiotic group continued to lose weight, for a total of 11.5 lbs per person.

The women consuming probiotics lost twice as much weight over the 24-week period of the study as the placebo group. The researchers also noted a drop in the appetite-regulating hormone leptin in the probiotic group, as well as a lower overall concentration of the intestinal bacteria related to obesity.

Dr. Tremblay said probiotics may act by altering the permeability of the intestinal wall. By keeping certain pro-inflammatory molecules from entering the bloodstream, they may help prevent the chain reaction that leads to glucose intolerance, type 2 diabetes, and obesity.

While the study focused on only one strain of Lactobacillus rhamnosus, Dr. Tremblay said other probiotics found in dairy products may have a similar effect. He emphasized the benefits of the bacteria are more likely to be observed in a favorable nutritional context that promotes low-fat and adequate fiber intake.

Are designer fibers on the horizon?

A newly-developed “designer” dietary fiber with an added potential prebiotic effect may eliminate the side effects of current treatment for irritable bowel syndrome (I.B.S.), which affects 10% to 20% of the population.

A research collaboration between a gastroenterologist at Rush University, Chicago, and a carbohydrate chemist at Purdue University, West Lafayette, Ind., led to the development of the new product, a natural starch derived from a mixture of seaweed and starch in which the release of starch fiber in the gastrointestinal tract may be delayed, slowed and controlled to occur in the colon, rather than in the stomach and upper intestine.

“This new product prevents the discomfort and bloating associated with current fiber therapies, while getting our new fiber into the colon and specifically distal colon where traditional fiber products typically do not reach and where many diseases of colon-like cancers develop,” said Ece Mutlu, principal investigator in the phase II trial that began at Rush University this past month.

In an earlier phase I study with 60 patients suffering from constipation, the new fiber was shown to be safe, better tolerated and with fewer side effects than currently available fiber treatments and it had a positive effect on intestinal microbiota composition by promoting the growth of “healthy” bacteria in the colon.

“We wanted to create a fiber with a slow rate of fermentation to avoid rapid expansion of the gut and thus decrease the likelihood of common side effects of conventionally used fibers like bloating,” said Ali Keshavarzian, professor and director of gastroenterology at Rush University.

The fiber also is designed to produce a high level of a short chain fatty acid, butyrate in order to promote gut health and to have a prebiotic effect for it to be a supplemental treatment for I.B.S.

The fiber is a targeted, controlled-release fiber that travels through the large intestine to be fermented by bacteria in the entire colon, including the descending (distal) colon where colon cancer, diverticulitis, ulcerative colitis and irritability commonly occur. The fiber may be designed to target different locations, according to the researchers. This enables the bacteria in the large intestine to receive nutrients from the fiber, which promotes overall gut health.

“We worked closely with Purdue University food scientist Dr. Bruce Hamaker to develop well-tolerated fiber with targeted delivery to the entire colon that could promote ‘gut health’ and possibly prevent and treat colonic diseases where changes in the gut play a key role,” Dr. Keshavarzian said.

A $2.5 million federal grant to develop the fiber was given to Nutrabiotix L.L.C., which is based in the Purdue Research Park, and is commercializing the patented designer fiber created by Drs. Hamaker and Keshavarzian.

Potential markets for the new fiber range between the dietary supplements category, functional foods and medical foods industries.