It has been known for decades that fiber is beneficial for the digestive tract. Yet, every so often a study declaring that to be unfounded would pop up and ignite some controversy. Today, the evidence could be said to be overwhelming that fiber in the diet is vital, not only for health, but for total well-being.
A systematic review and meta-analysis published in The Lancet early this year suggested a causal relationship between a high-fiber diet and reduced incidence of non-communicable disease. That is, consuming greater daily amounts of dietary fiber leads to reduced body weight, total cholesterol, and systolic blood pressure.
Other recent studies are elucidating mechanisms by which gut microbiota impact several diseases and providing a better understanding of how microorganisms affect the gut-brain axis. And those microorganisms thrive on fiber.
Other studies have been “drilling down” to reveal how different fibers change the composition of the gut microbial community and can help fight against rising disorders such as metabolic syndrome and type 2 diabetes. In conjunction with this, new sources for dietary fiber are expanding the choices available for inclusion in better-for-you food and beverage products.
Aging populations and new diets, as well as a deeper understanding of fiber needs and benefits for every age demographic, are creating greater demand for fiber in food. Formulators can leverage current research and trends to create products that not only deliver better nutrition, but also provide intervention and treatment to mitigate or prevent disease.
It’s impossible to talk about fiber and health without discussing the gut microbiome. The bacteria in the digestive system form a complex and synergistic ecosystem. Gut microbes make up about 1% or more of the body weight of a healthy individual and contain more than 100 times the number of genes in a human being.
Gut microbes interact with their host body in multiple ways. They break down indigestible dietary components (especially fiber); provide energy to colon cells; contribute metabolites that affect metabolic functions; and even produce compounds that can aid in immune function.
FOOD FOR THOUGHT
Gut microbiota can be influenced via the diet by ingestion of fiber in addition to probiotics, prebiotics, and phytochemicals. Targeting specific bacteria implicated in specific diseases is leading to new therapies and dietary interventions. One of the biggest areas of research, however, is how the interaction of fiber with the microbiome, and their balance, affect cognitive and brain health.
Research has demonstrated that butyrate, one of the short-chain fatty acids (SCFA) produced by gut bacteria after they feed on fiber, can positively impact brain health via several mechanisms, such as promoting expression of genes responsible for regeneration. This indicates that ingesting specific fibers to affect SCFA production could potentially aid in the treatment of disorders such as autism, schizophrenia, and neurodegenerative diseases.
Perhaps one of the most established health benefits of eating a fiber-rich diet is weight management. This has been studied comprehensively in adults and recently has been investigated in children as a means to combat childhood obesity.
Digestive regularity is another highly touted benefit of fiber consumption, especially in light of the recent flood of research indicating that such regularity has a far-reaching impact on the rest of the body’s health.
Emerging research also shows the impact a high-fiber diet may have in management of type 2 diabetes, leading to lower A1C levels via changes in gut microbial composition. New studies are revealing lesser-known health influences of fiber and highlighting new ways in which this ingredient can benefit consumers, such as reducing allergies, impacting mood and sexual function, and improving skin and bone health.
FROM INFLAMMATION TO IMMUNITY
There is an abundance of research suggesting that manipulation of the gut microbiome could aid in reducing inflammation and managing autoimmune disorders. Such diseases as rheumatoid arthritis and multiple sclerosis are on the rise in Western countries.
Epidemiological evidence suggests a link between increased risk of asthma and the notoriously fiber-poor Western diet. Conversely, diets with better nutrient density and higher fiber, such as the Mediterranean diet, are associated with decreased risk of developing asthma. Some animal studies also have suggested high-fiber diets could protect against asthma.
A recent study published in Scientific Reports indicated that non-fermentable fiber might present a new method to help reduce autoimmune responses and even could be used as a new treatment strategy against multiple sclerosis. Results from animal studies demonstrating diet-induced compositional changes in gut microbiota suggested that long-chain fatty acids could play a role in suppressing autoimmune responses.
It has been established that the gut microbiome plays a key role in immunity due to interaction with gut-associated lymphoid tissue. Thus, fiber intake can confer positive benefits on the immune system.
A study published last year in the Journal of Nutrition showed that, in children aged 3-6 years, daily supplementation with 6 g fructans (a mixture of short- and long-chain varieties) resulted in significantly higher Bifidobacterium and Lactobacillus populations and significantly lower incidence of fever that necessitated medical attention.
This study supports the growing body of evidence that fiber and prebiotic supplementation aid the immune system. It further highlights that such benefits can be realized even at an early age.
SKIN AND BONES
The gut microbiome and microbial populations change during aging, and emerging evidence suggests the diversity of gut bacteria decreases with age. While many factors contribute to the signs and symptoms of an aging body, it is scientifically plausible that dietary intervention that enhances the diversity of the microbiome could lead to better aging.
Polysaccharide fibers called beta-glucans — found in oats, barley, sorghum, and other grains, as well as in mushrooms, yeast, seaweed, and algae — can provide a number of health benefits, including lowering cholesterol, managing blood glucose, and boosting immune function. But recent research has shown that beta-glucans also promote skin health through mechanisms such as antioxidant activity, anti-wrinkle activity, and moisturization.
A recent review highlighted the skin-health properties of beta-glucans from oatmeal, yeast, and mushrooms, and suggested beta-glucans could be used in cosmetics and pharmaceuticals, expanding the applications of this fiber beyond digestive health.
Another aspect of aging involves bone health, and fiber can play a significant role here as well. While it has been known that SCFAs play a role in immune function, it also has been shown that SCFAs can assist in bone health. Researchers in Germany using animal subjects fed a high-fiber diet determined that SCFAs play a role in regulation of bone mass by preventing bone resorption.
The short-chain fatty acids also positively impacted osteoclast metabolism by preventing osteoclast differentiation. The researchers believe this is due to SCFAs themselves, and not specific microbial species.
While resistant starches and maltodextrins have been around for a while, research continues on the tremendous health benefits provided by these sources of dietary fiber. A current study published in Nutrition Research examined the effects of resistant maltodextrin on Bifidobacteria levels and found the counts were significantly increased by daily ingestion of 25g of resistant maltodextrin.
Another study examined the impact of potato-based resistant starch on adults aged 70 years and up. Daily consumption of 30g resulted in significantly improved blood glucose levels, insulin levels, and insulin resistance, indicating that resistant starches could be helpful in reducing risk factors for type 2 diabetes in older persons.
Green banana flour is a new ingredient that can be exploited for its fiber and resistant starch content, as well as its low glycemic index. Additionally, bananas have antioxidant capacity as a result of phenolic compounds present in both banana peel and pulp.
An interventional study examining the effects of green banana flour consumption on overweight women was recently conducted at the Universidade Federal de Viçosa in Brazil. The participants were instructed to add green banana powder to milk, yogurt, or fruit juice for consumption during breakfast.
Women in the study with metabolic syndrome exhibited decreased systolic blood pressure and fasting glucose levels with the high-fiber, resistant-starch flour. These results were not observed in female participants without metabolic syndrome.
For formulators, green banana flour also can be used in baked goods, such as cakes and pastries. A study published in Food Chemistry examined the impact of substituting portions of wheat flour with mechanically fractionated green banana flour in layer and sponge cakes. Up to 30% of wheat flour could be replaced with banana flour, with only small decreases in sensory results.
However, for sponge cakes, banana flour led to lower cake volume and increased hardness. Using fine banana flour minimized these changes in sponge cakes as compared to coarse flour. Incorporating banana flour into the cake formulations led to increased content of dietary fiber, resistant starch, and phenolic compounds, as well as greater antioxidant capacity.
Green banana flour has been used successfully as a partial fat replacer in other products. In bologna-type sausages, such usage met with favorable sensory acceptability. Additionally, ice cream made with green banana flour has received positive sensory evaluations.
PEAS AND SEEDS
The yellow pea has gained surprising traction in the last decade as a source of protein ingredients, but it is also a great source of dietary fiber. A study on the use of pea fiber in addition to wheat bran in pork meatballs resulted in increased sensations of satiety and fullness in healthy men, as compared to meatballs without fiber.
Researchers in Sweden and Denmark explored the use of a fiber-rich fraction from yellow peas in pasta-like sheets. The fraction tested contained 38% fiber, in addition to 21% protein and 37% starch. As the content of the fiber-rich fraction was increased, water uptake was greater and cooking loss was reduced, all while maintaining an al dente texture. Another study showed that the addition of 5% pea fiber in cake had similar texture and volume to the control cake.
The growth of the gluten-free trend has brought a number of flours from seeds, such as chia, hemp, flax, and quinoa, to the market. Flour from these seeds is typically high in fiber as well as protein, and as such, it can provide a boost of these nutrients in food formulations. Looking at chia as an example, reviews of the research to date indicate that chia can reduce inflammation, improve blood glucose levels, and decrease diastolic blood pressure.
Fiber-rich powder from cactus seeds also can be used to enhance fiber and antioxidants in food products. Researchers at Suez Canal University in Egypt showed that, while the use of cactus-seed flour decreased expansion and breaking strength of extruded rice-based products, sensory attributes and the nutritional profile were significantly improved.
Agroindustrial byproducts, such as the peels and rinds of fruits and vegetables, are the subject of new studies on — and efforts to use — ingredients derived from them in food formulations. One of the most effective cases of such “upcycling” has been fiber derived from citrus peels.
This now $100 million business is built on citrus fiber’s double duty as an excellent clean-label emulsifier and texturizer (with outstanding rheological properties) for bakery formulations, as well as its considerable potential impact on health.
In addition to citrus fiber being high in indigestible fractions, it also retains measurable amounts of bioactive antioxidants, such as polyphenols and flavonoids. Some of the vitamin C in citrus fiber also remains intact during processing. Building on this, a recent study determined that citrus peels exhibit some anti-cancer activity.
Prickly pear peel is another novel source of fiber ingredients. It, too, contains both dietary fiber and polyphenols. A new study published in the journal Food Chemistry examined the nutritional value and functional properties of three varieties of prickly pear peel. Fiber content ranged from 19-25% (dry basis), the greater proportion of which was present as insoluble fiber.
All three powders exhibited superior hydration properties as well as water- and oil-retention capacity, thereby demonstrating their ability to be used as functional ingredients that provide nutritional benefits.
The water-holding capacity of fiber ingredients can reduce purge and improve the juicy characteristics of meat products. Researchers in Mexico recently conducted a quantitative descriptive analysis on cooked sausages formulated with cactus pear fiber and pineapple fiber. They found the formulations were evaluated favorably, with slight differences in odor, texture, and taste attributes as compared to the control.
Other similar fiber ingredients also have been used in meat products. A study published recently in the Journal of Food Science highlighted the use of a functional carrot powder in sausages. Interestingly, stress placed on carrots via shredding resulted in carrot powder with increased fiber and phenol content. It should be noted that, in this study, sausages made with carrot powder had lower sensory scores than the control. However, all products tested were rated as acceptable.
Wine grape pomace flour (WGPF) is yet another byproduct that can be used in food products as a source of fiber and polyphenols. Scientists in Chile conducted a trial, feeding burgers made with 7% WGPF once daily to male volunteers possessing markers of metabolic syndrome. The WGPF resulted in significant decreases in glycemia and insulin resistance.
Fasting insulin concentrations also decreased but were not significantly different, implying improved insulin sensitivity. The researchers discussed that while fiber and antioxidants are thought of separately in dietary terms, the two are closely related, as fiber helps transport these phytochemicals to the intestines.
Many of these new fiber ingredients contain both fiber and antioxidants, allowing them to be a part of a multifaceted approach to improved nutrition and mitigating the risk of chronic disease. Scientific literature also has reported the use of similar ingredients, such as artichoke fiber in biscuits, lemon fiber in hamburgers, and jackfruit rind powder in bread.
When working with fiber ingredients, it is important to select an ingredient that will survive the processing conditions and final product parameters, including pH, temperature, and shear, while limiting any negative organoleptic impact. With beverages, soluble or easily dispersible fiber formats will enjoy greater success than heavy insoluble fibers that tend to settle.
When formulating high-acid foods, fiber ingredients that are not susceptible to acid hydrolysis are best. The oil- and water-binding capacities of fibers make them useful in reducing purge and cook loss in meat products and pastas. And, of course, incorporating sources of fiber that also contain phytochemicals gives additional health benefits and marketing advantages.
Between the existing sources of fiber and the ever-growing list of novel ingredients, virtually any food formulation can be fiber-fortified to provide numerous health benefits to consumers.
Devon Gholam, PhD, is a highly skilled 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 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 firstname.lastname@example.org.