The Role of Inulin in Human Health and Sustainable Food Applications

Abstract

Inulin, a naturally occurring prebiotic soluble fiber, has been a staple in our diets since prehistoric times. It has been identified in over 36,000 plant species- including chicory, Jerusalem artichoke, onion, garlic, bananas, and agave. The polysaccharide has gained recognition for its positive effect on gut microbiota via fermentation and cultivation of gut healthy bacteria. However, inulin has also exemplified numerous significant health benefits beyond the gut including weight loss, improved glucose and lipid metabolism, increased mineral absorption, immunomodulator effects. Additionally, the robust, versatile, and prevalent nature of inulin offers opportunities to ameliorate growing challenges in sustainability. This chapter sheds light on the role of inulin as a prebiotic, including its impact on gastrointestinal and overall health; as well as its applications in fostering sustainability, particularly in the food, socio-economic, and environmental sectors.

1. Introduction

Within the corridors of the gastrointestinal tract resides a lively ecosystem, known as the gut microbiota. This biome plays a crucial role in maintaining health and preventing disease [1, 2]. Advancements in research have shown that diet significantly affects these microbial communities [3].

Prebiotics are non-digestible dietary fibers that selectively promote beneficial bacteria in the gut, such as Bifidobacteria and Lactobacilli [4]. Unlike probiotics, which are foreign live microorganisms that are then ingested; prebiotics act as substrates to nourish already residing beneficial microbes present in the gastrointestinal tract. Although prebiotics have silently played a crucial role in human nutrition since ancient times, the definitive term of prebiotic was first introduced in 1995 by Marcel Roberfroid and Glenn Gibson; defining substances that induced a growth or activity of beneficial microorganisms in the gut [5]. In the compass of prebiotics, one of the most highly researched topics is inulin.

This review aims to elucidate the growing significance of prebiotics such as inulin in the context of health management practices. Moreover, this chapter will explore the benefits of inulin beyond simply the context of healthcare; to encompass escalating concerns of public health, sustainability, and economic adversities.

2. Role as prebiotic and applications in health

One of the many ways inulin exerts a positive influence on the gut microbiome is by cultivating beneficial bacteria. It accomplishes this through numerous mechanisms including selective fermentation, production of short chain fatty acids, supplying nutrients, establishing a competitive advantage regarding beneficial bacteria; in effect wholly improving the gut microbial population, and gut barrier [6, 7].

Prebiotics, such as inulin, may even be considered superior to probiotics in certain facets. These benefits lie chiefly in the character of the prebiotic as a nondigestible fiber; serving as a food source for further stimulation and growth of local beneficial gut bacteria. In doing so, it creates a more stable and diverse microbiota, that is sustainable over a longer period. Probiotics, on the other hand, introduce new bacteria which could immediately boost certain bacterial strains; however, the effects may be short-lived and require continuous intake to maintain beneficial effects [8]. Additionally, prebiotics can survive the digestive process reaching the colon intact. Probiotics may be more sensitive to the acidic environment, leading to a lower number reaching the intestines [9]. Moreover, probiotics carry the risk of bacteremia, sepsis or endocarditis, particularly in the immunodeficient population. Of note these risks have not been reported in studies with prebiotics [10]. This is likely due to their slower mechanism of action on resident local bacteria rather than introduction of foreign microbes.

Beyond its influence on the gastrointestinal biome, inulin contributes to vitamin synthesis, absorption, weight management; and glucose and lipid metabolism. It has also been studied for its potential role in secondary cancer risk reduction, via its immunomodulatory and anti-inflammatory properties [1, 2]. Other studies, regarding the gut-brain pathway, suggest that gut dysbiosis may translate to mood, behavioral, and cognitive disorders [1, 11].

2.1 Fostering beneficial gut bacteria

Inulin resists digestion in the upper GI tract. Its molecular structure- β-(2- > 1) glycosidic bonds- is largely unaffected by salivary amylase and pancreatic enzymes like α-amylase and maltase [9, 12]. This is an anticariogenic benefit. When inulin reaches the colon, it is selectively fermented by beneficial bacteria like Bifidobacteria (bifidogenic effect) and Lactobacilli. These bacteria possess the enzymes required to break down inulin into simpler compounds that can be utilized for growth and energy [13]. Specifically, Lactobacillus and Bifidobacteria spp contain an enzyme called inulinase, a β- fructofuranosidase, that breaks down inulin into fructose by cleaving the β-2,1-glycosidic bonds [14–16]. Through selectively promoting the proliferation of these beneficial bacteria, inulin helps beneficial bacteria outnumber and establishes a competitive advantage against pathogenic bacteria [17].

2.2 Gut barrier

In addition to preventing diseases by diminishing the pathogenic bacteria population, the beneficial bacteria stimulated by inulin also enhance the gut barrier integrity, specifically the mucosal lining. This fortified gut barrier prevents the passing of harmful substances and pathogens which can contribute to cancer development and illnesses. Lactobacillus spp. strengthen the mucosal barrier by promoting tight junction (claudin-1, zonula occludens-1 and occludin) integrity, and in doing so, reduce permeability, and prevent pathogen or toxin entry [18, 19]. On the other hand, the Bifidobacterium species enhance gut barrier integrity by producing short chain fatty acids- acetate, butyrate. Of note, butyrate is produced indirectly through the bifid shunt. The byproduct of this shunt, lactate, is utilized by other bacteria like Eubacterium Halii and Anaerostipes caccae to produce butyrate [20, 21]. These SCFAs aid in health maintenance of intestinal epithelial cells and support immune responses in the gut.

2.3 Short chain fatty acids

Short chain fatty acids (SCFAs) have many benefits. They serve as a major source of energy for colonocytes, help maintain the integrity of the gut barrier; and hold anti-inflammatory properties [7, 22].

Inulin produces SCFAs through fermentation in the colon by Bifidobacteria and Lactobacilli [23]. After the enzymatic breakdown of inulin into simpler sugars, the bacteria metabolize these compounds through various anaerobic fermentation pathways; of which the primary fermentation products are SCFAs—acetate, propionate, butyrate. The specific SCFA produced depends on the bacterial species. Acetate is the most abundantly produced SCFA that is involved in influencing gut pH and fostering beneficial gut bacteria. Propionate can be absorbed through the bloodstream and has effects in glucose, lipid metabolism and improved insulin sensitivity [24–27]. Butyrate is typically produced by “cross-feeder” bacteria, Anaerostipes spp and Eubacterium Halii, through metabolization of Bifidobacteria’s major end products acetate and lactate [19].

SCFAs provide significant energy for colonocytes. This energy is utilized in enhancing performance of colonocytes, maintaining the integrity and function of the gut barrier, promoting healthy cell growth, and reducing the risk of conditions like leaky gut syndrome. SCFAs additionally support the barrier function through their capability of enhancing the expression of tight junction proteins, which helps restore the epithelial barrier function that is often compromised in diseases such as inflammatory bowel disease (IBD) [18, 19]. SCFAs also decrease pH; creating an acidic colon environment that is hostile to pathogenic bacteria and favors beneficial bacteria. Moreover, SCFAs play a feature role in immunomodulation. In response to stimulus markers like concanavalin-A and immobilized anti-CD3 monoclonal antibodies, SCFAs stimulate T cells, cytokines, and regulatory T cells. Through this, SCFAs prevent the migration and over-activation of lymphocytes, thereby reducing excessive immune activation and colonic inflammation [28].

SCFAs, particularly butyrate, have anti-inflammatory properties. Through inhibition of the activation of nuclear factor kappa B (a key character of the inflammation pathway), SCFAs reduce the production of pro-inflammatory cytokines such as interleukin- 1β (IL-1β), tumor necrosis factor-alpha (TNF-α), and interleukin-6 (IL-6) [22].

Clinically, the mechanisms of SCFAs have been employed to manage various GI conditions such as IBD (Crohn’s disease, ulcerative colitis); and diversion colitis. Notably, clinical research has revealed low total SCFA levels (p = 0.014); and low butyrate producing bacteria (p < 0.0001) in ulcerative colitis; highlighting SCFAs pivotal role in chronic inflammatory processes. More pertinently, this conveys the potential of inulin supplementation as adjunctive therapy in IBD conditions [29].

Studies have been conducted regarding SCFAs’ role in reducing carcinogenic compounds. There are several mechanisms which have been postulated to do this, including many we have already discussed: reducing the pH (inhibiting harmful bacteria which produce carcinogenic byproducts); anti-inflammatory effects (chronic inflammation has been linked to cancer development); providing energy to colonocytes (maintain energy for gut barrier integrity and prevent exposure from translocation of malignant compounds); cellular signaling (ex: HDAC inhibition [which can stimulate and employ the inhibitory role of regulatory T cells]); regulating gene expression and inducing apoptosis for normal cell turnover [28].

2.4 Weight loss and modulation of lipid, glucose metabolism

Inulin has been linked with weight loss through several potential mechanisms including decreased caloric intake, increasing satiety, modulating hunger hormones, enhancement of gut health, improving insulin sensitivity, reducing fat absorption, promoting thermogenesis, and long-term effects on body composition. Inulin is postulated to be about 2.5 kcal (potentially overestimated as inulin and other NDFs’ interactions with digestion of proteins and fats, has been posited to decrease the caloric value of the meal as a whole) [30–32]. Inulin forms a gel-like substance in the digestive tract which: through distension, stimulates vagal receptors in the gut and aids in promoting feelings of fullness and satiety; and through the morphology of the gel-like substance itself, aids in slowing down carbohydrate absorption (in turn preventing blood glucose spikes) [32]. This reduces overall food intake and controls appetite which can contribute to weight loss [33]. Clinical trials have found that oligofructose (a subgroup of inulin) may influence hormones involved in appetite regulation; specifically decreasing ghrelin and increasing peptide YY (PYY) [24]. Ghrelin is a peptide hormone which is simply known as the “hunger hormone” because it stimulates appetite. Hence blood levels are highest before meals. PYY, on the other hand, suppresses appetite. Inulin, by reducing ghrelin levels and increasing PYY levels, reduces appetite and in turn promotes weight loss. Additionally, the study showed, in comparison to placebo, reduction plasma glucose and insulin levels in individuals with obesity. A randomized controlled clinical trial showed significant reduction in fasting blood sugar, HbA1c, total cholesterol, triglyceride, LDL-c, and increased HDL-c, further positing improvement of the metabolic profile with inulin supplementation [34].

Some clinical trials have shown a significant increase (p = 0.003) in GLP-1 secretion with inulin supplementation which supported additional metabolic and comorbidity benefits including improved diastolic blood pressure, reduced waist circumference, and reduced fasting blood sugar [35, 36]. Additionally, GLP-1 agonists, such as Ozempic, have been increasingly used to promote weight loss and glucose metabolism. GLP-1 is secreted from the L-cells in the intestine which increases insulin secretion and reduces glucagon secretion, thereby reducing insulin resistance and stabilizing blood sugar levels in diabetic patients. GLP-1 is also involved in appetite regulation by acting on the central nervous system. Inulin induced increases in GLP-1 can promote feelings of satiety and reduce food intake by activating anorexigenic neurons in the hypothalamus [37]. This action helps in managing body weight and reducing obesity-related complications. GLP-1 promotes the sustenance of pancreatic beta cells (via stimulation of cAMP, insulin receptor substrate-2 activity, and finally Akt, which is responsible for insulin movement from the intracellular compartment to the cell membrane by GLUT transporters, where it proceeds with its function of glucose uptake) [38]. This dual action helps in maintaining effective glucose control and improving metabolic health.

Through the production of SCFAs, especially butyrate, inulin has been linked with improved insulin signaling and sensitivity. This is done through activation of G-protein coupled receptors (GPCRs). SCFAs bind to receptors like GPR41, GPR43 and GPR109A which increase insulin sensitivity through their effects on inflammation and energy metabolism pathways [39]. SCFAs are associated with lower fasting insulin levels and improved Homeostatic Model assessment for Insulin Resistance (HOMA-IR) which is indicative of better insulin sensitivity. Inulin additionally may aid in weight loss through binding with bile acids; thereby promoting their excretion and reducing fat absorption [40]. This process would also lower cholesterol levels. SCFAs have also been linked to promote thermogenesis by stimulating brown adipose tissue, increasing energy expenditure and thermogenesis [41]. Inulin has been linked with changes in body composition. Through the apparent effect of increasing satiety, reducing overall calorie intake, inulin contributes to better weight management and a decrease in obesity related complications [42].

2.5 Mineral absorption

The bioavailability of calcium in our current food products is insufficient. For example, the bioavailability of calcium from dairy products is estimated to be around 30–35%. Lamentably, for individuals with dietary restrictions, the option of calcium from vegetables- like spinach, kale, and broccoli- contain calcium bound to oxalates, which can form insoluble salts and diminish calcium absorption. The bioavailability of calcium from these sources is much lower, generally around 5–15% [43].

Many studies support inulin’s influence on mineral absorption. One study showed daily consumption of inulin, over 8 weeks and 1 year time periods, significantly increased calcium absorption and enhanced bone mineralization during pubertal growth [44]. Another study found increased calcium absorption over a 3-week period with inulin supplementation in normocalcemic young females at or near menarche [45]. Inulin supports mineral absorption through increasing passive diffusion, solubility and bioavailability, enhancement of gut microbiota, improvement of intestinal barrier function, ion exchange, modulation of intestinal transporters, and effects of the byproducts of fermentation [28, 46–51].

Inulin is composed of multiple hydroxyl groups (-OH)- which allows for chelation and formation of complexes with calcium ions (Ca2+) [22]. This complex formation helps keep calcium ions in a soluble form throughout the digestive process; and increase bioavailability and absorption. Advancements in biotechnology have already developed modified inulin, in the form of calcium phosphorylated inulin complex. These groups contain atoms with negative charges which are then able to form additional, fortifying bonds with Ca2+ ions. The extra phosphate groups themselves allow for enhanced chelation and stability through additional interactions. Moreover, the phosphate groups can contribute to the overall hydrophilicity of the molecule, improving solubility and stability [52]. Additionally, inulin (through SCFAs) increases calbindin levels and influences transcellular active calcium transport [46]. Several animal studies report an increase in calcium and magnesium with inulin and/or SCFA supplementation; some also note an increase in transporters TRPV6, Calbindin-D9k, PMCA1b [47–51]. Additionally, in 2007, a study by Abrams et al., postulated that with inulin supplementation, increased calcium absorption occurred in the colon, rather than the small intestine [53]. TRPV6 is highly expressed in the colon of humans, rats, and mice [54, 55]; with other studies also noting increased mRNA expression levels of TRPV6 in the colon [48]. This raises further support regarding the colonic influence of inulin (through its byproduct SCFA) in increasing calcium absorption through increased transporter activity in the colon; as well as increased overall solubility of calcium due to reduced environmental pH.

2.6 Vitamins

These beneficial bacteria also assist in the synthesis of essential vitamins- primarily Vitamin B, and K. These vitamins are crucial in cognition, energy production, fat and amino acid metabolism, DNA repair, hemoglobin synthesis, coagulation, and much more. Many studies have linked reduced levels of vitamin B6, B12 with development of GI cancers [56–58].

Other studies demonstrate Lactobacilli’s ability to produce SCFA and vitamins such as B2, B9, B12. Additionally, the research demonstrates that various Lactobacillus isolates produced more or less of certain vitamins. For example, KGL3A isolate produced the most B2, while WTS4 produced the highest amounts of folate [59]. This supports the advantages of fostering a diverse microbiome with inulin or other prebiotics; as opposed to pre-formed, limited strains available in probiotics.

In addition to inulin aiding in the synthesis of vitamins through stimulation of various beneficial bacterial strains; inulin also supports absorption through its other functions. These previously discussed mechanisms include fortifying the tight junction integrity to allow for efficient nutrient transport while preventing pathogen entry; and preventing inflammation. Inflammation damages areas of absorption and decreases surface area for absorption. Vitamin deficiencies due to inflammation are apparent in IBD patients. Inulin prebiotic supplementation may be pivotal for patients suffering from vitamin deficiencies due to IBD, leaky gut, short bowel syndrome, post resection, post radiation, restricted diets, autoimmune disorders, infections (with Helicobacter Pylori or Clostridium Difficile which cause increased intestinal permeability), or aging (also linked to increased tight junction permeability); among others [60].

2.7 Colorectal cancer

Inulin can lower the risk of colon cancer though its beneficial effect on SCFAs. Butyrate, a SCFA, induces apoptosis in colon cancer cells, stimulating colon motility, reducing inflammation, and inhibiting tumor cell progression [22]. Butyrate potentially induces apoptosis through the JNK MAP kinase pathway; and histone deacetylase inhibition, which leads to hyperacetylation of histone proteins [61]. This change in histone acetylation affects gene expression involved in cell cycle regulation and apoptosis, promoting the expression of pro-apoptotic genes such as P21, WAF-1/CIP1; while down regulating anti-apoptotic genes such as BCL–2 [52]. This alteration facilitates apoptosis of cancer cells by disrupting mitochondrial function and activating the caspase cascade. As aforementioned, butyrate induces apoptosis through the mitochondrial pathway by reducing the mitochondrial membrane potential. This reduction triggers a release of cytochrome C from the mitochondria into the cytosol where it forms complexes with apoptotic protease activating factor–1 (apaf-1) and caspase-9, which activates caspase-3 leading to execution of apoptosis [62, 63]. Butyrate also elevates the levels of reactive oxygen species which further damages the mitochondrial membrane, enhances the release of cytochrome C and promotes apoptosis via the cytochrome C/caspase- 3 pathway [64–66]. Butyrate interacts with specific GPCRs (GPR41, GPR43), modulating signaling pathways that influence cell survival and apoptosis. GPCRs are also known as free fatty acid receptors (FFAR). Of note, FFAR 2/3 has been found significantly in colon regulatory T cells (T reg) compared to other tissues; suggesting activation of these receptors can inhibit pathways such as NF-κB (which is involved in inflammation and cell survival) thereby promoting apoptosis [67]. Activation of GPCRs by short-chain fatty acids can reduce inflammation in the colon which is a major risk factor for colon cancer. GPR43 enhances the production of mucus and tight junction proteins, which protect the gut lining from wandering harmful pathogens and toxins that could induce carcinogenesis [22].

Through epigenetic modulation, butyrate can alter acetylation of histone and non-histone proteins. In this way, butyrate can modulate gene expression patterns involved in apoptotic signaling and the immune response [61].

Inulin and its byproducts prevent dysbiosis by maintaining a healthy gut microbiota. Dysbiosis is a condition linked to colon cancer due to chronic inflammation. Pathogenic bacteria- which can produce proinflammatory compounds such as lipo- polysaccharides- can trigger cyclical inflammatory responses, causing DNA damage and carcinogenesis. It is noteworthy that approximately 20% of cancer diagnoses have been linked to chronic inflammation [68–70]. Similarly, some pathogenic bacteria produce secondary bile acids such as deoxycholic acid and lithocholic acid (through fermentation of primary bile acids, such as: cholic acid, chenodeoxycholic acid) which have been shown to damage DNA and promote tumor formation [71]. Other harmful bacteria have been known to produce toxins such as colibactin which directly induces DNA damage [72]. Dysbiosis and the resulting decreased SCFAs production, can weaken mucosal variant and lead to increased permeability allowing harmful bacteria and thereby products to enter the bloodstream and surrounding tissues again promoting inflammation and carcinogenesis. Dysbiosis is also associated with epithelial to mesenchymal transition (EMT), a process where epithelial cells acquire migratory and invasive properties facilitating metastasis. Pathogenic bacteria can induce EMT by producing proteases that disrupt cell adhesion and increase cell motility [73]. A balanced gut microbiota can produce more SFAs, reinforcing the protective effects of butyrate against colorectal cancer and other malignancies (Table 1).

Application	Characteristic/Role
Gut bacteria	Production of beneficial bacteria like Bifidobacteria and Lactobacilli [13] Competitive advantage [17] Positive effects as below, notably thru SCFA byproducts [23]
Gut barrier	Lactobacillus involved in tight junction integrity [18, 19] Bacteria produce SCFAs which maintain intestinal epithelial cells and support immune responses in the gut [23]
Short chain fatty acids	Serve as sources of energy for colonocytes, help maintain the integrity of the gut barrier, create an acidic environment; hold immunomodulatory, and anti-inflammatory properties [7, 22]
Weight loss	Decrease caloric intake, increase satiety, modulate appetite hormones, enhance gut health, improve insulin sensitivity, reduce fat absorption; promote thermogenesis, and long-term effects on body composition [30, 32]
Modulation of lipid, glucose metabolism	Lipid: through weight loss, as above; reduced LDL-c, and increased HDL-c. [30, 32, 34]. Glucose: through weight loss, as above; as well as increased GLP-1 [35, 36]; activation of G-protein coupled receptors (GPCRs) [39]
Mineral absorption	Multiple hydroxyl groups (-OH) which allows formation of complexes with calcium ions (Ca2+) [22] Calcium complexes stay in a soluble form; with increased bioavailability and absorption [22, 52] Increases calbindin levels [46] and influences transcellular active calcium transporters [47–51]
Vitamins	Lactobacilli: produces vitamins such as B2, B9, B12. [59] Tight junction integrity: efficient nutrient transport [18, 19] Anti-inflammatory [22]; Inflammation damages areas of absorption and decreases surface area for absorption.
Colorectal cancer	Induces apoptosis at a cellular level. Various pathways, including acetylation in malignant cells, JNK-MAP pathway, mitochondrial pathway [61–63] Through promotion of healthy gut microbiome; reduced inflammation [68–70]

Table 1.

Summary of the role of inulin in health applications.

3. Role in sustainability

Inulin can be found in various renewable plant sources and can contribute to growing sustainability efforts globally.

3.1 Inulin plants

The chicory root is the most common and economically significant source of inulin. It can be cultivated in most environments, and requires fewer fertilizers and pesticides compared to other crops [74]. The Jerusalem artichoke is another source of inulin; which can grow in diverse climates and soil conditions. It can be employed in crop rotation systems to enhance soil fertility, reduce the need for harmful chemical use; and thus, improve soil conditions [75]. The agave plant- more commonly associated with tequila, mezcal production- is also gaining popularity for inulin extraction. Tequila itself is sourced from the “piña,” which is the core or heart of the plant. Further use of other parts of the plant for inulin allows for reduced waste. Moreover, agave plants are highly water efficient and drought tolerant, making them well-suited for regions with limited water- like its native homeland, Mexico [76]. Yet another source is the dandelion root, from which inulin can be harvested from wild or cultivated plants. The dandelion root shines in its contribution to biodiversity and the lack of need for sensitive farming practices [77–79].

Overall, these renewable inulin sources contribute to sustainability efforts in that they are widely available, hardy, do not require intensive agricultural practices; and can be replanted and harvested annually or even more frequently- ensuring a sustainable supply of inulin. Increased focus and implementation of these plants offers additional benefits such as reduction of atmospheric carbon levels and greenhouse gasses. Their deep root systems, particularly of chicory and Jerusalem artichoke, can improve soil aeration and health. Pertinently, the multitude of plant options that produce inulin encourages biodiversity; providing ecosystems for pollination and habitats for wildlife.

3.2 Antibiotic resistance

Exposure to antibiotic raised meat can disturb the delicate ecosystem of the animal, as well as the human, gut. Resistance caused by exposure can make it difficult to treat more severe infections [80]. Prebiotic in animal feed can provide increased nutrition and the growth of beneficial bacteria; bestowing increased immuno-protective effects in livestock [79]. This, in turn, reduces antibiotic necessity in livestock farming, and antibiotic residue in the environment. Additionally, this promotes healthier, more well-nourished livestock, which can utilize feed more efficiently and have better growth rates; thereby reducing the overall resources needed for farming and minimizing waste production.

3.3 Synthetic additives

Synthetic additives, including artificial sweeteners (such as aspartame, sucralose, sacralin) and fat replacements (such as Olestra, Caprenin) can have various consequences on the environment. Artificial sweeteners can be toxic to land and aquatic ecosystems. Through its toxic by-products [81], it has been linked to inducing behavioral disorders and malignancy in humans, and aquatic life [81–85]. Artificial sweeteners can also induce plant morbidity and death [86]. They have also been noted to impair nutrient cycling and soil fertility; which further diminishes plant health, agricultural product activity and ecosystem stability [87].

Inulin, with its milder taste and beneficial properties, can be employed as a natural alternative to harmful artificial sweeteners in foods and beverages. By replacing these chemicals with the biodegradable inulin, we can improve public health and reduce production and disposal of these toxins in our environment-thereby decreasing their long term (and some not fully understood) effects.

3.4 Plastic reduction

Plastic presents significant detrimental disruptions to the environment through resource depletion. The extraction process from fossil fuels itself contributes significantly to greenhouse gas emissions. Notably, microplastics have been detected in more than 100 aquatic species; including those that are staple to the human diet [88]. Another disturbance is worsening waste management. This is most apparent in developing countries, where garbage management is often nonexistent due to cost [88].

Due to its biodegradability, inulin-based bio-products- such as bioplastic and biodegradable films- offer eco-friendly alternatives to pursue amidst growing environmental concerns regarding excess plastic use. One 2018 study by Cao et al., explored inulin and chitosan blends to create films with a bonus antioxidant and antimicrobial component; another research discussed inulin enhanced PVA-films with antibacterial properties for potential medical wrap use [89, 90]. Iolanda et al., experimented with the transformation of cardoon inulin into polyhydroxyalkanoate with applications in the food packaging sector [91]. These bio-products would naturally break down into carbon dioxide and water through microbial action. Implementation of these products would lead to reduced dependency on fossil fuels; and offer a solution to most of the pressing issues discussed above (regarding plastic, wildlife, habitat destruction, climate change, waste management). Veritably, as this field is new, the concept of inulin based plastic products faces challenges in developing cost-effective processing techniques and ensuring that these bio plastics meet mechanical and durability standards that traditional plastic offers. Despite these challenges, inulin-based bio-products stand as valuable commodities through their prevalence, potential for being a plastic replacement, biodegradability, and even more so through their antimicrobial and antioxidant properties.

4. Role in economic growth

The Global market for prebiotics was evaluated at USD 5.3 billion USD 2020 and is predicted to be worth around 9.6 billion USD by 2025. The compound annual growth rate is estimated at 12.5% between this period. The market includes Beneo (Germany), ADM (US), DuPont (US), among others [92]. This growth can be attributed to the rising interest in healthier lifestyles, preventative healthcare; awareness of digestive health benefits, environmental concerns, and the growing use of inulin in common products. Well-known brands such as Chobani, FiberOne, Nestle, General Mills, Bayer, and Loreal have already implemented inulin across a variety of their products.

4.1 Healthcare cost reduction

Inulin can reduce the risk of chronic diseases such as diabetes, obesity, cardiovascular diseases, and dental caries [93]. The medical costs and productivity losses due to diagnosed diabetes, in 2022, was estimated to be approximately $413 billion USD [94]. Similarly, the medical costs of obesity have been projected to reach around $173 billion USD each year [95]. Cardiovascular diseases result in losses of nearly $251 billion per year and additionally inflict approximately $156 billion loss in the context of diminished occupational productivity. Notably, losses from cardiovascular conditions are projected to top $1 trillion by 2035 [93]. Dental care results in a loss of 34 million school hours each year, and in terms of monetary value dental disease costs our healthcare system approximately $46 billion [96, 97]. Lower incidence and complications of these diseases reduce healthcare costs for both individuals and governments, freeing up resources that can be allocated to other sectors of the economy.

4.2 Food industry growth

Inulin is increasingly used in the food industry as a functional ingredient. The growing demand for inulin could spur further innovation and investment in food technology and processing sectors, thereby stimulating economic activity and creating jobs. Some yogurt brands, such as certain varieties of Activia yogurt; and Yoplait’s Light yogurt, use inulin as a fat replacer to achieve smoother consistency without increasing fat levels. Similarly, inulin can be used in baked goods like cookies, muffins and cakes to replace fat content while maintaining taste, moisture, and texture. It is noteworthy that recently inulin has also been making its rounds into beverages with a new young crowd favorite being the Poppi prebiotic soda. This soda brand posits less sugar, less calories, new intriguing flavors, and advertisement of inulin’s health benefits of improving gut health, immunity, and skin health. Although the company was only created around March 2020; it has been postulated that the company had made over 100 million USD in sales in 2023, just 3 years after its creation [98, 99]. It respectably has joined the functional soda category which is estimated to be valued at approximately $173 billion USD by 2025 [98].

Moreover, inulin’s function in prolonging shelf life of food products can reduce food waste [100]. Globally, about 1.3 billion tons of food is wasted annually, which is a loss of approximately 1 trillion USD per year [101]. By extending the shelf life of food, inulin can help reduce these losses. Even if implementation can reduce food waste by just 1%; that would equal around 10 billion USD saved annually. This also results in cost savings for manufacturers and retailers. Similarly, products that last longer are more liked by consumers, leading to increased sales loyalty. A survey found that 60% of shoppers were concerned that the shelf life of foods had decreased; and more than 70% were mindful of food waste when purchasing food [102]. Longer shelf life also translates to a more efficient logistics and inventory management, reducing cost related to frequent restocking and transportation.

Inulin’s attributes as a calorie, sugar, fat, and stabilizer substitute, is attractive to customers seeking healthy options. The growing consumer demand, as well as rapid financial growth of emerging businesses in the prebiotic field, beckons food manufacturers to develop new products and expand their market share. Additionally, this spurs further innovation and investment in food technology and processing sectors, thereby stimulating economic activity, and creating jobs.

4.3 Agricultural sector

Another potential field of influence includes agriculture. The agriculture industry notably contributed 1.530 trillion USD to US gross domestic product (GDP) in 2023, which is a 5.6% share. Agriculture, including forestry, fishing and related activities, employs approximately 2.6 million people directly; indirectly that number stretches out much further [103]. Cultivating crops rich in inulin can provide income opportunities for farmers, especially in regions where these crops can be grown effectively. Chicory root is a hardy plant that grows in dry climates and does not require sensitive farming, which allows for use of arid land deemed “unusable” for cultivation of most crops and provides new opportunities for farmers specializing in these crops, potentially leading to increased agricultural production and income. This diversifies agricultural production and can improve rural economies by providing stable markets for these crops.

4.4 Research and development

Studies exploring the health benefits of inulin, especially topics of public interest increase consumer interest and demand. The current inulin extraction process is complex and costly, first through a high heat diffusion method (70–80C), then additional purification processes due to impurities from the high temperatures. This process has led to potential innovations such as pulsed electric fields, ultrasound, and microwaves for extraction. The benefits of these processes include saved energy, time, money, resources; and increased production due to milder temperatures which would decrease impurities and eliminate further purification steps [104, 105]. There are also significant ongoing developments being made in the field of inulin-based bio-products [89–91]. Additional new advancements- like inulin use for creation of nano- medicines for cancer therapy [106] or modification of inulin to create enriched mineral supplements [107] can attract more funding, encourage collaboration between academia and industry, and lead to development of new products and processes which can positively influence public health at large, offer new solutions to improved management of chronic diseases and drive economic growth.

5. Conclusion

The multifaceted exploration of inulin has illuminated a broad spectrum of opportunities spanning various disciplines: from disease prevention and health promotion; to its applications in enhancing agricultural practices and addressing environmental challenges. The myriad of benefits inulin offers paves way for scientific advancement and socioeconomic development. As public interest in personalized health care grows, so does research and funding into the applications of inulin in various sectors.

Conflict of interest

The authors declare no conflict of interest.