America’s appetite for gut-friendly products continues to be ravenous. Consumers are eagerly seeking foods and beverages that help them maintain a healthy digestive tract. This is also evidenced by GoogleTrends. Recent data from Google revealed that the number of US web searches for “improving gut health” increased 250% in the past year alone.

Connected to and helping to drive this interest in the digestive tract is the expanding consumer awareness that having a healthy gut means more than just being regular. The science uncovering the connections between digestive health and both immunity and mental health/well-being has created a generation of tuned-in consumers as well. According to the aforementioned Google analytics, interest in “anxiety and gut health” rose 200%, suggesting that individuals have a growing curiosity about how gut health affects the brain.

Health-conscious consumers willingly and experimentally modify their diets in search of solutions to bloating, indigestion, constipation, low energy levels, and weight issues. Mounting evidence suggests the gut and its community of microbes act as the internal switchboard connecting one’s diet to manifested feelings that go beyond the stereotypical and once taboo-to-discuss function of bowel movements.

Thanks to candid social media influencer-led conversations and health practitioner recommendations, consumer interest in digestive health products continues to become part of the entire health experience. This paradigm shift into the mainstream has opened the door for functional foods and beverages to specifically target the lower g.i. tract.

Ingredients such as prebiotics, probiotics, and fiber have achieved widespread usage in functional foods in recent years. They also, in turn, have fostered greater research into new ingredients and new varieties of the tried-and-true ingredients for better digestive health. Some of the ingredients attracting attention in recent years merit closer examination.


Mid-June brought a timely decision and statement from US Food and Drug Administration (FDA). Commissioner Scott Gottlieb, M.D., ruled on the agency’s efforts to better equip consumers with nutritional information about dietary fiber in their food.

Following are Gottlieb’s comments from a June 14, 2018 press release.

Increasingly, Americans are seeking healthy food options, whether they’re eating out or dining at home. Their ability to choose healthy foods starts with their ability to understand what’s in their food in the first place. Public surveys suggest that Americans want food makers to be transparent about what is in a product and how it’s made. The food industry has responded by innovating and reformulating their products. Among other things, they’re boosting fiber content, and curbing the amount of sodium and sugar.

At the same time, we at the US Food and Drug Administration are doing our part to ensure consumers have updated, science-based information to help them make more informed dietary choices.

In March, I announced a comprehensive, multi-year Nutrition Innovation Strategy intended to drive additional actions that the FDA can take to reduce preventable death and disease related to poor nutrition. Part of this effort includes taking final steps on the new Nutrition Facts label.

This is our first overhaul of the food label in more than 20 years. It’s aimed at making sure that consumers have access to an updated label that’s based on updated science and provides more information to empower them to choose healthful diets. I also recognize that it’s crucial for the FDA to provide clear expectations so that industry can meet our new labeling requirements and that we provide the greatest flexibility possible, while still maintaining an approach that is grounded in rigorous science.

As part of those efforts, today the FDA issued decisions on citizen petitions regarding additional dietary fibers. We also issued a guidance that will allow food manufacturers to count these fibers when calculating the total amount of fiber per serving to declare on the Nutrition Facts label. They can also be counted as fiber on the Supplement Facts label. 

The eight new fibers are: mixed plant cell wall fibers (a broad category that includes fibers like sugar cane fiber and apple fiber, among many others); arabinoxylan; alginate; inulin and inulin-type fructans; high amylose starch (resistant starch 2); galactooligosaccharide; polydextrose; and resistant maltodextrin/dextrin.

Our work is not done. We have received additional petitions asking for additional fibers to be recognized in a similar fashion to the eight dietary fibers we are identifying today. We are actively evaluating these additional requests, working through the petitions and, in some cases, supplementary information provided by the petitioners, in an efficient manner. We recognize the importance of providing timely responses so that food makers have certainty around their manufacturing decisions. We also welcome the submission of additional petitions in the future as science emerges and as new ingredients are identified. Our expectation is that we will continue to evaluate additional dietary fibers on a rolling basis, and we expect that additional fibers may be recognized in the future.

All of these decisions build off of the FDA’s evidence-based definition of dietary fiber published in 2016, which stated that dietary fiber declared on the updated Nutrition Facts label can include certain naturally-occurring fibers that are “intrinsic and intact” in plants as well as seven other added isolated or synthetic fibers that are well recognized by the scientific community for having physiological benefits. Before the FDA established this definition, manufacturers could declare synthetic or isolated fibers as fiber on the label without evidence that these fibers had beneficial physiological effects on the body. Consumers can be assured that non-digestible carbohydrates counted as fiber on the new Nutrition Facts label have health benefits grounded in scientific evidence. Eating foods rich in dietary fiber, as recommended by the Dietary Guidelines for Americans, can help cholesterol levels, increase feelings of fullness (satiety) resulting in reduced calorie intake, and increase the frequency of bowel movements.

We are taking a flexible approach to dietary fiber, allowing for the possibility of additional fibers to be added to the list of those meeting our dietary fiber definition if the scientific evidence shows they are physiologically beneficial. In addition to other relevant scientific literature, we carefully reviewed submitted petitions requesting that the FDA allow food manufacturers to count other non-digestible carbohydrates as fiber on the Nutrition Facts label. These included sugar cane fiber, apple fiber, and inulin, among others. We also issued a final guidance in March clarifying the information needed and the approach we planned to use to include additional non-digestible carbohydrates in our fiber definition. Petitioners were given the opportunity to revise their filings based on our more detailed guidance.

The decisions regarding most of the eight additional non-digestible carbohydrates come as a result of such petitions. But it’s important to note that these determinations are based on a careful review of the scientific evidence suggesting that each of these additional fibers has a beneficial physiological effect. The FDA also issued two denials to petitioners because we did not agree that the evidence submitted met the scientific standards, as described in our March scientific guidance. We’re also working expeditiously to complete our review and responses for the other petitions that we haven’t yet responded to.

The FDA is issuing new guidance today to express our intent to exercise enforcement discretion, permitting manufacturers to count these eight additional fibers in the dietary fiber declaration on the Nutrition Facts label pending completion of the agency’s rulemaking regarding adding additional fibers to the dietary fiber definition in FDA regulations.

Food manufacturers now have additional clarity to help them move forward to update their labels as needed ahead of the compliance date for the updated Nutrition Facts label, which is Jan. 1, 2020 for manufacturers with $10 million or more in annual food sales and Jan. 1, 2021 for smaller manufacturers. Our goal is to make sure that consumers can trust that the latest, tasty fiber-rich snack food or cereal that comes on the market can offer them some real health benefits.

We’re committed to ensuring that consumers have updated information so they can be empowered to make positive changes in their diets. Access to reliable, science-based information about food and diets not only helps consumers make healthier choices, but it also inspires food manufacturers to compete to offer products that have the healthy attributes that consumers seek and that food makers can declare on labelling. These efforts can help encourage food patterns that are consistent with the dietary guidelines, can help reduce chronic diseases, and can help ultimately alleviate health disparities through improved nutrition.

The FDA, an agency within the US Department of Health and Human Services, protects the public health by assuring the safety, effectiveness, and security of human and veterinary drugs, vaccines and other biological products for human use, and medical devices. The agency also is responsible for the safety and security of our nation’s food supply, cosmetics, dietary supplements, products that give off electronic radiation, and for regulating tobacco products.

Guar Fiber

With more than 120 recently published clinical studies behind it, guar fiber has a recognized track record for bringing balance to the digestive tract.

Some of the documented health benefits range from relief of occasional constipation and diarrhea to active prebiotic effects and management of blood sugar, hunger, and cholesterol. Studies also show that guar fiber delivers these benefits without the undesirable side effects common to some other dietary fibers, such as excessive gas, abdominal cramps, and bloating.

As a prebiotic, guar fiber has a positive effect on the gut microbiome, as several clinical studies have shown. Guar fiber promotes the proliferation of beneficial Bifidobacteria and Lactobacillus bacteria, and diminishes negative or harmful bacteria in the gut.

Guar fiber has been used in products for more than 25 years and has a long history of safety and efficacy. Guar fiber is one of the only low fermentable oligo-, di-, and mono-saccharides and polyols (FODMAP) soluble fibers (Monash University Low FODMAP certified).

One new product on the market containing guar fiber is a tasteless and odorless powder by Regular Girl. The powder is a blend containing 5g guar fiber along with probiotics from the Bifidobacteria lactis strain. The powder can be added to beverages or stirred into foods.

When added to water or other clear liquids, the Regular Girl product dissolves completely, without clouding. Because guar fiber is stable across a wide range of temperatures, pH, and freeze-thaw cycles, it is able to maintain shelflife and effectiveness in numerous food and beverage products.

Go Psycho

The gut-brain axis is an emerging area of research that focuses on the connection between the gut microbiome and its impact on the central nervous system and psychiatric disease. Researchers are working hard to better understand the mechanisms by which gut microbes impact neurological health, including actions on the vagus nerve, interactions with digestive metabolites, balancing of fatty acids, gut hormone signaling, and immune responses.

“There is a bidirectional communication between the gut microbiota and the brain, maintained by endocrine and neurocrine mechanisms,” Suravi Patra, MD, of the Department of Psychiatry at the All-Indian Institute of Medical Sciences, Delhi, explained in an article published in the Indian Journal of Pharmacology. “The brain can influence the microbiota composition, while the intestinal microbiota can influence brain neurotransmitter levels with consequent effects on emotions, behavior, and pain.”

Arising out of this growing knowledge about the gut-brain axis is a new concept in “better for you” ingredients: psychobiotics. Psychobiotics could be a new avenue for capitalizing on this synergy in digestive health. Defined as “bacteria, which when ingested confer health benefits in patients with psychiatric diseases,” these microorganisms exhibit anti-inflammatory effects similar to other probiotics, but they also produce neurotransmitters such as serotonin and gamma-aminobutyric acid (GABA).

It is believed that the influence of microbes on serotonin and GABA levels in the gut affects brain chemistry. Cells in the g.i. tract called “enterochromaffin cells” produce approximately 90% of the serotonin in the human body. Serotonin also is secreted by some species of Enterococcus and Escherichia, whereas GABA is produced by Lactobacillus and Bifidobacterium.

Serotonin is a neuroactive compound well-known and studied for its effects on mental and emotional health and well-being. But serotonin also plays a role in digestive health. Scientists studied the effects of Lactobacillus acidophilus and Bifidobacterium longum on the level of serotonin transporter mRNA in intestinal epithelial cells in vitro. It turns out that a balance between the release and inactivation of serotonin is required to achieve equilibrium in the gut.

Research revealed that serotonin levels are different in patients with irritable bowel syndrome (IBS) with predominant constipation versus patients with IBS with predominant diarrhea. Serotonin transporters, which inactivate serotonin, were upregulated in cells treated with probiotics.

These connections led to reviews of the potential of psychobiotics. It has been noted that treatment with probiotics is physiologically and psychologically beneficial in patients with disorders such as IBS and Crohn’s disease, as often there is comorbidity with anxiety and depression.

While most of the work on the mechanisms of psychobiotics has been elucidated by animal studies, a number of human clinical trials have shown promise for probiotics and improvement of mood. While many of the human studies look at the effects on persons with digestive health issues, one study, published in the British Journal of Nutrition, examined the effects of Lactobacillus helveticum R0052 and Bifidobacterium longum R0175 in healthy human volunteers. The researchers found the probiotic treatment provided measurable benefit countering general signs of anxiety and depression.

Preliminary results from a double-blind randomized study conducted at the University of Rome-Tor Vergata showed that probiotics can have a positive impact on the mental well-being of women who are obese or suffer from normal weight obese syndrome (NWO), described as having a normal body-mass index but with higher total body fat and lower total body lean mass.

Women enrolled in the study took a probiotic suspension containing various lactic acid bacteria species from the genera Bifidobacterium, Lactobacillus, Lactococcus, and Streptococcus. After three weeks on the probiotic, the NWO and preobese/obese groups had a statistically significant lower BMI and fat mass.

Psychopathological scores and eating behavior for both groups also were improved. Because the sample size was small, more studies with larger groups are needed to verify the results, but the initial results are promising enough to consider such probiotic applications for future food formulations.

Since GABA is a popular supplement on its own, it is worthwhile to consider whether food formulators should formulate with probiotics, ingredients such as GABA, or a combination of the two. It also is worth noting that certain common compounds in foods are converted, in small amounts, into serotonin and melatonin, a sleep regulating neurotransmitter, in the gut.

Suitable gut microbes have the potential to be genetically engineered in the future to metabolize tryptophan in specific ways to benefit consumers. The interplay of bacteria and neurologically significant compounds opens many possibilities for future food products.

A Little S’more

Both herbal/folk medicine and functional foods provide methods of interacting with the gut microbiome. Popular botanicals for digestive health have included such flavorful, phytochemical-filled ingredients as fennel, ginger, mint, and chamomile.

As science keeps dipping back into the traditional medicine well, other botanicals are moving into the limelight. Marshmallow (Althaea officinalis) root and flower extracts are examples of emerging ingredients for formulators seeking compounds that help maintain a healthy gut with a beneficial balance of good microbes.

Marshmallow, commonly found in the Middle East, is often prescribed in that part of the world for relief from inflammation and gastritis. The plant has been used in Europe for relief from irritation of mucous membranes and cough.

A recent study conducted at the University of Müenster, Germany, assessed the effects of aqueous extract and raw polysaccharides from marshmallow root in vitro. The extract was found to stimulate epithelial cell activity and proliferation. The study also revealed that the raw polysaccharides were adsorbed onto the cell surface of fibroblasts, the cells that are key players in wound healing, cell and extracellular matrix structure, and collagen building.

New animal studies have examined the effects of marshmallow flowers. A water extract of the flower was given at various doses and found to have meaningful effects on various biological markers. These included increased serum high-density lipoprotein (HDL) cholesterol, decreased liver enzyme activity, protection against ulcers induced by ethanol, and anti-inflammatory activity.

A later animal study confirmed the protection marshmallow flower extract confers against gastric ulcers. This experiment observed the effects of aqueous extracts of both marshmallow flower and ginger on subjects with indomethacin-induced ulcers. The researchers proposed that the protective mechanism of the extracts is due to their antioxidant properties.

Polyphenols and Antioxidants

It has long been postulated that a diet high in fruits and vegetables contributes to better overall health. Taking advantage of the fibers, polysaccharides, and polyphenols present in fruits, vegetables, and grains is another way to marry herbal medicine with functional food.

In recent years, much research has been performed on polyphenols and antioxidants as they relate to better health, including digestive health. The related forms of polyphenols known as anthocyanins, procyanidins, and proanthocyanidins (PACs), are found in several plant-based foods, including berries, cereals, chocolate, wine, and tea.

PACs exhibit bioactivity beneficial to human health, including antioxidant activity, diabetes prevention (via participation in glucose homeostasis), anti-inflammatory activity, antimicrobial action against pathogens, and inhibition of carcinogenesis. These diseases and dysfunctions are interlinked with gut health.

A recent review regarding the use of functional foods and herbal medicine to treat and prevent diseases, published in Frontiers in Microbiology, highlighted the significance of apple procyanidins. A study in Scientific Reports demonstrated that mice fed a diet high in sucrose and fat gained less weight and had decreased inflammation when fed highly polymeric apple procyanidins.

Scientists at the USDA determined that purple and red rice bran extracts containing anthocyanins and PACs increased glucose uptake in mouse adipocytes (fat cells), suggesting the extracts assist glucose homeostasis and aid diabetes management. Both of those conditions are known to impact digestive health.

PACs from cinnamon also gained attention in the last decade for their anti-diabetic potential. Because polyphenolic compounds are sometimes bitter, incorporating them into finished products can be problematic. Scientists at the Universidade de São Paulo in Brazil recently published a study showing that spray chilling can be used to add PACs from cinnamon into solid lipid microparticles.

Vegetable fat was used as the carrier for the bioactive compounds. Using such a lipid base can result in stability lasting up to 90 days. The spray-chilling process also can mask astringent or bitter notes sometimes associated with cinnamon PACs.

Ingredient Update

While the use of ingredients such as probiotics, fibers, resistant starches, and inulin for functional food formulations is not a new concept, research continues to build support for these important ingredients.

A recent study examined the probiotic potential of Enterococcus hirae F2, a lactic acid bacteria strain found in the gut of Indian major carp fish. The study showed these bacteria survived simulated digestion, inhibited pathogens such as Staphylococcus aureus and Salmonella typhi, and had the ability to form curd, which could be helpful in yogurt and other probiotic dairy applications.

Inulin, a fructan polysaccharide, and fructooligosaccharide (also called “oligofructose” or “oligofructan”), are both widely utilized prebiotic fibers in a variety of market segments. Commonly derived from chicory root and other sources, they have a solid record of benefits for gut health.

A recently published study from the University of Memphis, TN, conducted on adult volunteers by Randal Buddington, PhD, of the University of Tennessee Health Sciences Center, demonstrated that  daily supplementation of 15g of oligofructose from chicory root significantly balanced digestion while being well-tolerated.

With most of the US ingesting half or less than half of the 25g minimum daily recommendation for fiber, such ingredients are a boon to both consumers and the product developers wishing to help them meet these needs from just a few sources during the course of the day.

These fibers incorporate easily into products such as baked goods and smoothies, and even confections such as chocolate. They contribute a slight sweetness to a formulation, but with only about a third of the calories of sugar, flour, or starch. They work especially well in conjunction with high-intensity sweeteners to mask off tastes and round out the sweetness profile.

Inulin also can be sourced from agave. A study in the Journal of Nutrition showed agave inulin supplementation at 7.5g per day (a level previously determined by the same researchers to be well-tolerated in humans) increased fecal Bifidobacterium content and total dietary fiber consumed by the study participants correlated positively with fecal butyrate levels.

Microbe Food

Beneficial probiotic bacteria in the lower g.i. tract feed off of the prebiotic fibers and generate the short-chain fatty acid (SCFA) butyrate. Butyrate serves as the preferred energy source for epithelial cells in the colon.

Butyrate and other SCFAs, as metabolites of prebiotics in the gastrointestinal tract, have been implicated in health benefits such as fluid and electrolyte uptake regulation and anti-inflammatory responses. Arabinoxylans, another fiber type found in the cell wall of wheat grain, have been shown to exert immunomodulatory effects via interactions with gut bacteria.

Resistant starch has benefited from the new surge in interest in digestive health. More processors and product developers are turning to the ingredient for its ability to work on multiple levels in formulations and in the body. Resistant starch, too, is a fermentable carbohydrate that generates butyrate and other SCFAs.

In the body, resistant starch performs several beneficial functions. Per its name, it is resistant to digestion, so it makes its way to the colon, acting as a fiber to regulate collection and movement of materials for expulsion and helping clear the body of potentially deleterious substances.

Dozens of research studies back the efficacy of resistant starch in helping to improve digestive function, balance blood sugar, manage weight, and increase satiety, both through the physical actions of its fiber-like capacity, and chemically via stimulation of satiety hormones.

In formulations such as baked foods, resistant starch can replace up to 25% of wheat flour while not only maintaining the structure and rising capacity, but also helping risen items by adding a few more percent volume. Resistant starch can help with clean label formulations, as it can be labeled simply as starch from its source.

As evidenced here, there are several ingredients, both old and new, that food formulators can utilize to create science-backed healthful products for today’s digestive-savvy consumers. The toolbox for foods aimed at digestive health will no doubt continue to increase as research continues to explore the interaction of new probiotics and botanicals with the gut microbiome.

As science helps to better understand the mechanism of how fibers and polysaccharides interact with the gut and other organ systems, formulators will have the ability to create food products that deliver benefits for digestive health and the holistic health it has come to represent.

Devon Gholam, PhD, received her doctorate in food science from Purdue University. She is a food scientist with extensive experience in product development and research, including food product design, formulation/reformulation, sensory methodology, statistical analysis, experimental design, and analytical techniques such as HPLC, GC, and FTIR. She has worked for such food and ingredient companies as Roquette America Inc., Ganeden Biotech Inc., and Kellogg Co. In addition to product consultation, she also provides technical support, communications, presentations, white papers, and other food and ingredient marketing tools. Reach her at