Sorghum and health: An overview of potential protective health effects

Abstract

Whole‐grain sorghum foods may elicit health‐promoting effects when consumed regularly in the diet. This review discusses key functional sorghum grain constituents, including dietary fiber, slowly digestible and resistant starches, lipids, and phytochemicals and their effects on metabolic processes that are associated with the development of chronic diseases, such as heart disease and diabetes. Currently, the range of sorghum food products available to consumers is limited globally, hindering the potential consumer benefits. A collaborative effort to innovate new product developments is therefore needed, with a focus on processing methods that help to retain the grain's favorable nutritive, health‐enhancing, and sensory attributes. Evidence for sorghum's purported health effects, together with evidence of impacts of processing on different sorghum foods, are presented in this review to fully elucidate the potential of sorghum grain to confer health benefits to humans.

1. INTRODUCTION

Whole‐grain foods are prominent in healthy eating patterns (Miller, 2020) and are featured in many dietary guidelines around the world (National Health & Medical Council, 2013; Phillips, 2021). Numerous epidemiological and interventional studies demonstrate that regular whole‐grain consumption lowers the risk of diabetes and heart disease (Aune et al., 2016; Hu et al., 2020), improves blood glucose regulation ( Li et al., 2023), assists with weight management (Nirmala Prasadi & Joye, 2020), and may lower the risk of some cancers (Gaesser, 2020). Sorghum (Sorghum bicolor (L.) Moench) is a whole‐grain cereal food that, like other whole grains, exhibits some prohealth and disease‐mitigating properties (McGinnis & Painter, 2020). To reveal sorghum's potential health benefits, studies have investigated its nutritional and bioactive components, notably phytochemicals, starches, nonstarch polysaccharides, proteins, and fats (de Morais Cardoso et al., 2017; Ducksbury et al., 2023). These grain constituents have been linked to effects on energy balance (Stefoska‐Needham et al., 2017), satiety regulation (Stefoska‐Needham et al., 2016), glycemic control (Poquette et al., 2014), and lipid regulation (Suhasini & Krishna, 1991). Favorable impacts on antioxidant (Khan et al., 2015; Girard & Awika, 2018; Zhang et al., 2019) and anti‐inflammatory processes (Yang et al., 2009; Zhang et al., 2019) as well as on gut microbiota modulation (Martínez et al., 2010), have also been reported. Collectively, these sorghum grain constituents may favorably impact metabolic health and markers of disease, including body weight, thereby highlighting sorghum's potential role in chronic disease prevention (Stefoska‐Needham et al., 2017). This is particularly relevant in Western societies experiencing a high prevalence of obesity‐related chronic diseases (Boersma et al., 2020). To more comprehensively elucidate the health impacts of sorghum consumption, consideration must be given to methods used to manufacture and prepare sorghum‐based foods and meals, as these processing techniques may impact the potency of effects, either positively or negatively (Figure 1). Therefore, this paper aims to elucidate sorghum's position as a valuable food source for human consumption, by providing an overview of the evidence supporting (i) protective health effects of sorghum whole‐grain consumption and (ii) impacts of food processing on sorghum foods’ prohealth properties.

FIGURE 1.

Interrelationships between nutritional/chemical profile, health effects and impacts, and processing methods of sorghum foods.

2. PROTECTIVE HEALTH BENEFITS OF SORGHUM CONSUMPTION

Human studies examining protective health benefits of sorghum consumption are limited. Early studies, those published prior to the new millennium, focused on micronutrient metabolism (Maclean et al., 1983), iron absorption from grains (Hurrell et al., 2003), dietary effects (Fedail et al., 1984), protein digestibility (Maclean et al., 1981) and oral rehydration therapies (Molla et al., 1989). Since 2010, more human trials and experimental research have been conducted to investigate effects of sorghum consumption on metabolic health and disease markers, as evidenced in two recent systematic reviews of the literature (Ducksbury et al., 2023; Simnadis et al., 2016). The current evidence base confirms that sorghum elicits several beneficial effects, including improvements to markers of oxidative stress, blood glucose, and lipid levels, and it may play a role in satiety‐promoting mechanisms to facilitate weight control. The outcome measures evaluated in these recent appraisals of the evidence base (Ducksbury et al., 2023; Simnadis et al., 2016) represent major risk factors for disease pathogenesis, hence strengthening the support for sorghum's role in health and disease prevention.

2.1. Effects on energy balance, satiety sensations, and body weight

Sorghum whole‐grain represents an ideal food for the purpose of weight management, given that higher whole‐grain consumption has been linked to more sustainable weight management (Cho et al., 2013). Sorghum's energy value is estimated at 1380 kJ/100 g (USDA FoodData Central, 2023); however, the metabolizable energy is likely to be lower on account of lower rates of starch and protein digestibility, as demonstrated in experimental research. For example, evidence from feeding studies shows reduced weight gain in animals consuming whole‐grain sorghum feeds, especially the slowly digested tannin‐rich sorghum varieties (Al‐Mamary et al., 2001; Muriu et al., 2002). There is a paucity of studies exploring sorghum intake and energy balance; however, Shen et al. (2015) investigated the impacts of sorghum‐resistant starch (RS) on body weight changes in a sample of 60 overweight or obese rats over an 8‐week treatment period. The findings revealed that overweight rats consuming a high‐fat diet enriched with 30% sorghum RS experienced significantly less weight gain compared to rats fed a diet without sorghum RS (p < 0.05). Further, the production of two appetite hormones derived from adipose tissue, leptin and adiponectin, was significantly altered (p < 0.05) in the sorghum RS groups, indicating a potential mechanism of action for sorghum RS in the regulation of food intake and body weight.

In two separate clinical trials, Stefoska‐Needham et al. (2017) and Anunciação et al. (2019) conducted a comparison of the impact of whole‐grain sorghum to whole‐grain wheat foods on weight loss in overweight adults following an energy‐restricted diet. Stefoska‐Needham et al. (2017) observed that both intervention groups experienced significant weight loss (sorghum 5.2 kg; wheat 5.4 kg, p < 0.001). No differences between the two groups were identified. On the other hand, Anunciação et al. (2019) observed significant weight loss in the sorghum intervention group (1.5 kg weight loss, p < 0.05), but not in the wheat control group. With only these available high‐quality published studies, more evidence from new randomized controlled trials is needed to fully understand and confirm the effects of regular whole‐grain sorghum consumption on weight management, particularly in the longer term.

Mechanistically to understand effects on body weight changes, investigation of satiety‐enhancing effects is necessary given the relationship between appetite regulation and weight control. Stefoska‐Needham et al. (2016) explored the satiety effects of white, red, and brown flaked whole‐grain sorghum biscuits through an acute meal test study. Both appetite‐related biomarkers (notably gut hormones) and subjective ratings of satiety were measured. For all the sorghum test foods, subjective satiety ratings were significantly higher when compared to a wheat‐based control biscuit (p < 0.05); however, no significant differences were noted between the three sorghum biscuits. Favorable increases in the appetite‐relating hormones glucagon‐like peptide‐1 (GLP‐1), gastric inhibitory peptide (GIP), and, peptide‐tyrosine‐tyrosine were also reported for the sorghum biscuits (p = 0.018, p = 0.031, p = 0.036, respectively) compared to a wheat control. Notably, the red sorghum biscuit exhibited the best results, potentially attributed to a unique flavonoid called 3‐deoxy anthocyanidin (3‐DXA) found in red sorghum grains. The 3‐DXA creates complexes with proteins in the sorghum food matrix, slowing protein digestibility, which is known to extend satiety. Cisse et al. (2018) investigated effects of a sorghum porridge meal on subjective satiety and rate of gastric emptying compared to millet porridge, plain potato, wheat pasta, white rice, and couscous. Participants rated subjective satiety higher for the sorghum porridge at the 2‐hour mark, compared to the millet porridge (p < 0.05), though no significant differences were observed between sorghum and the other test foods. The rate of gastric emptying was slower after consuming the sorghum porridge when compared to wheat pasta and rice (p < 0.05); however, no significant differences were noted between sorghum and the other test foods. In these studies, the higher levels of dietary fiber, RS, and slowly digestible starches (SDS) in whole‐grain sorghum likely increased satiety due to effects on the glycemic index of foods and on appetite‐regulating hormones.

2.2. Effects on glycemic control

Slow starch digestibility has been observed following the consumption of sorghum foods, both in animal feeding trials and laboratory settings, intimating potential beneficial impacts on human postprandial glycemic and insulinemic responses. Several animal feeding studies have reported improved glucose metabolism when sorghum is included in the diet compared to sorghum‐free diets (Appleton et al., 2004; Chung et al., 2011; Kim & Park, 2012; Park et al., 2012). However, a limitation in some of these studies is the lack of specification regarding the type of sorghum extract used, making it difficult to ascertain whether the observed effects are attributed to phytochemical, dietary fiber, or macronutrient contents. Additionally, the physiological relevance of the concentrations of sorghum extracts is uncertain, particularly regarding their capacity to elicit blood glucose‐attenuating effects in humans at physiologically realistic doses. However, recent appraisals of the current evidence base confirm these favorable effects in adults with hyperglycemia (Abdelgadir et al., 2005; Lakshmi & Vimala, 1996; Mani et al., 1993; Prasad et al., 2015), as well as in normoglycemic adults (Anunciação et al., 2019; Mahgoub et al., 2013; Omoregie & Osagie, 2008; Poquette et al., 2014; Prasad et al., 2015; Stefoska‐Needham et al., 2016, 2017). In this collection of studies, the glucose‐attenuating effects were preserved to varying degrees following consumption of a wide range of foods (flatbreads, porridges, muffins, and breakfast cereals) that were manufactured using different processing methods. This variability in blood glucose attenuation is affected by the characteristics of the sorghum‐based foods consumed as influenced by cooking/preparation methods, grain‐refining processes (flour), and the chemical and nutritional composition of the end food product, such as whole‐grain and starch contents, fiber levels, and macro‐ and micronutrient profiles (Nishida & Martinez Nocito, 2007).

At the food level, the glycemic attenuating properties of sorghum can be attributed to SDS and RS in the different sorghum grain cultivars. Sorghum starch digestion is hindered by a complex protein network called prolamin, known to reduce enzymatic starch breakdown (Ezeogu et al., 2005). As a result, this promotes a slower and more sustained release of glucose into the blood circulation (Giuberti & Gallo, 2018). Additionally, the intricate outer structure of the grain may further restrict the enzymatic breakdown of RS in sorghum‐based foods (Raigond et al., 2015). Notably, the whole‐grain sorghum products investigated to date have consistently exhibited higher levels of dietary fiber levels compared to their whole‐wheat counterparts (Anunciação et al., 2019; Khan et al., 2015). On the other hand, test foods derived from refined sorghum grains have tended to contain lower levels of fiber and to be associated with increased glucose responses after consumption (Lakshmi & Vimala, 1996; Mani et al., 1993; Omoregie & Osagie, 2008; Prasad et al., 2015).

2.3. Effects on cardiovascular outcomes

Sorghum whole‐grain's lipid profile is beneficial to lipid‐lowering mechanisms in humans, which may improve risk factors linked to cardiovascular disease. The majority of sorghum lipids are neutral triacylglycerides (TAG), rich in poly‐ and monounsaturated fatty acids (Glew et al., 1997). However, there are only a few human studies that have evaluated the effects of sorghum consumption on cardiovascular outcomes, such as total cholesterol (TC), low‐density lipoprotein (LDL) cholesterol, high‐density lipoprotein (HDL) cholesterol, and TAG levels. A clinical trial by Suhasini and Krishna (1991) demonstrated significant reductions in TC and LDL cholesterol levels; however, the study design was flawed, and data regarding the composition of the test foods and the characteristics of the participants (including details of their background diets) was absent. Most of the evidence for potential favorable effects on cardiovascular outcomes has emerged from animal research investigating actions of a range of sorghum components (Ajiboye et al., 2016; Carr et al., 2005; Kim et al., 2015), such as policosanols (Guo et al., 2014) and tannins (Chung et al., 2011;Lee & Pan, 2003). Therefore, a translation of the encouraging findings from animal research into rigorous human research is needed to confirm the full extent of cardiovascular effects related to regular sorghum consumption in humans.

2.4. Effects on oxidative stress biomarkers and inflammatory processes

Chronic disease pathogenesis stems from inflammatory processes caused by the imbalance between the production of radical oxygen species (ROS) and their elimination from the body, also known as oxidative stress (Hussain et al., 2016). Polyphenols have been shown to disrupt enzymatic actions to reduce inflammation, thereby mitigating pathogenic processes (Hussain et al., 2016; Kumari et al., 2021). Colored sorghum grains, notably brown and red varieties, give rise to foods that are richer in polyphenols, flavonoids (including anthocyanins), and tannins compared to wheat, barley, millet, and rye (Ragaee et al., 2006) and have demonstrated strong free radical scavenging and anti‐inflammatory properties (Birhanu, 2021). This potency is particularly evident in red sorghum varieties, rich in 3‐DXAs (M. Li et al., 2021; Luo et al., 2020). In general, sorghum polyphenols are associated with greater antioxidant activity, and this property is often retained in end food products made via different food preparation processes (Xu et al., 2021). Studies in both healthy people and people living with an active disease have demonstrated that sorghum may improve biomarkers of oxidative stress and thereby may enhance antioxidant status clinically (Anunciação et al., 2019; Khan et al., 2015; Lopes et al., 2019). However, more clinical trials are needed across a range of chronic diseases to comprehensively evaluate the potency of these effects.

2.5. Effects on cell‐mediated immune responses

Cancer development is associated with cell‐mediated immune responses. Epidemiological evidence from populations in Africa and Asia where sorghum is consumed has consistently linked its consumption with reduced incidence of esophageal cancer, prompting further investigation into sorghum's potential role in chemoprevention (Chen et al., 1993; Isaacson, 2005; Loefler, 1985; Van Rensburg, 1981). To date, research exploring sorghum and cancer has involved mostly cancer cell‐line studies investigating antiproliferative, antimutagenic, and anti‐inflammatory effects involved in the mitigation of carcinogenesis. Using high phenolic sorghum bran extracts, Lee et al. (2020) and Cox et al. (2019) showed a significant dose‐dependent suppression of cell proliferation in human colon cancer cells. In another cell‐line study using HEpG2 and Caco2 cancer cells, high polyphenolic sorghum bran extracts also inhibited cancer cell growth through reactive oxygen species induction, cell cycle arrest, and apoptosis (Smolensky et al., 2018). Phenolic extracts derived from red, black, and tannin sorghum varieties have been shown to induce cell arrest and suppression of tumor growth in vivo in animal studies (Park et al., 2012; Wu et al., 2011). However, a considerable number of additional animal studies and in vitro studies are needed before justifying the use of sorghum extract in human clinical trials to test cancer‐related effects. Hence, it is more likely that epidemiological research will be conducted to understand sorghum's chemopreventive potential, together with mechanistic studies that will assist with the interpretation of findings.

2.6. Effects on the gut microbiome

The gut microbiome and human diseases are linked, and global research efforts are focused on investigating strategies to modulate the gut microbiota, and thereby mitigate disease development and progression (Gomaa, 2020). Diet plays an important role in modulating the composition and metabolic activity of the gut microbiota, with plant‐based and plant‐dominant diets showing favorable results (Stanford et al., 2020). A recent study by Lopes et al. (2019) has shown that whole‐grain sorghum foods, like other plant food, can also modulate the gut microbiota. In this study, the effects of a synbiotic sorghum meal on levels of uremic toxins (p‐cresyl sulfate and indoxyl sulfate) were investigated in people with kidney disease receiving hemodialysis treatment. In clinical practice, the levels of uremic toxins are used to monitor the extent of disease progression. When compared to a maize‐based control, the synbiotic sorghum meal resulted in greater drops in both p‐cresyl sulfate levels (p < 0.05) and indoxyl sulfate (p < 0.05) levels, while influencing favorable alterations to the gut microbiota composition. More evidence from human trials investigating the gut microbiota‐modulating effects of different sorghum foods on a range of pathophysiological processes (such as gut dysbiosis, oxidative stress, and inflammation) is warranted. This would add to the currently available evidence from animal research that indicates beneficial changes in the abundance and diversity of the composition of gut/colonic microbes, contributing to reductions in inflammation and oxidative stress (de Sousa et al., 2019; Gilchrist et al., 2020; Ritchie et al., 2015, 2017).

3. IMPACTS OF PROCESSING ON THE HEALTH BENEFITS OF SORGHUM‐BASED FOODS

All sorghum‐based products must undergo processing in order to be transformed from raw (or native) grains into appealing edible foods. Importantly they also need to retain their beneficial nutrient, health, and functional properties (Thielecke et al., 2021), which can be further influenced by consumer use and preparation. However, in Western societies, opportunities to appreciate these factors are limited as the range of available sorghum‐based foods is low compared to commonly consumed cereal foods (such as those derived from wheat) (Table 1). For example, in a cross‐sectional study of Australian supermarkets sorghum ingredients were only found in 6.1% of all ready‐to‐eat breakfast cereals and 2% of snack bars (Ducksbury & Stefoska‐Needham, 2022). Given that cereal grains are most commonly utilized in the production of certain products (bread and other bakery products, breakfast cereals, and cereal‐based snack foods), having few sorghum products may represent a barrier to enabling potential consumer benefits. For supporting research, regular consumption of sorghum would be required to expose the full spectrum of benefits. Given that a varied diet is desirable, food innovation is needed to broaden the sorghum food product range across more familiar food formats.

TABLE 1.

Examples of sorghum‐based food products.

Ready‐to‐eat breakfast cereals
Porridge    Flaked breakfast biscuits    Granola    Muesli

Bakery products/ingredients
Bread (e.g. flatbread, tortilla, injera, roti)    Baked sweet biscuits    Cake mixes    Sorghum flour and meal    Composite flours (e.g. combined with wheat, soy flour)

Snack Foods
Biscuit style bars    Cereal snack bars    Pretzels    Popcorn

Ready‐to‐eat meals/foods
Pasta    Noodles    Vegetarian patties

Beverages
Beer    Baijiu (Chinese colourless spirit)

Product briefs for new sorghum food product developments must also consider consumers’ expectations of what constitutes a health‐promoting cereal product. In keeping with nutritional standards reflected globally in dietary guidelines (National Health & Medical Research Council, 2013) and food regulations (European Food Standards Authority, 2023; Food Standards Australia New Zealand, 2023; United States Food & Drug Administration, 2023), consumers typically associate healthy cereal foods with higher levels of whole‐grains, dietary fiber, and antioxidant components, while being slowly digested and low in saturated fats and sodium (Heiniö et al., 2016). New “healthy” sorghum foods can have all of these attributes, in addition to being gluten‐free, while serving as alternatives to common grains such as wheat, rye, and oats.

Importantly new product development must be done with a focus on processing methods that help to retain the grain's favorable nutritive, health‐promoting, and sensory attributes.

Common examples of relevant processing methods include milling, flaking, fermentation, and various thermal treatments such as baking and steaming. These are all comprehensively reviewed in the literature (Khoddami et al., 2023; Taylor & Duodu, 2015). Other processing methods include puffing and popping (Castro‐Campos et al., 2021). The different processing methods have been shown to either positively or negatively alter the chemical composition and physical properties of both the sorghum grain and sorghum food matrix, influencing the effect that product consumption may have on metabolic processes (Khan et al., 2015; Stefoska‐Needham et al., 2016; Taylor & Duodu, 2015). At the food level, these impacts may include alterations to whole‐grain content, dietary fiber and starch composition, rate of starch digestibility (including the degree of starch gelatinization), nutrient bioavailability, and antioxidant capacity (associated with the degree of phenolic composition) (Khoddami et al., 2023; Rashwan et al., 2021; Taylor & Duodu, 2015). Thus, processing itself may influence the overall health‐promoting potential of the end food product.

As reflected in dietary guidelines (National Health & Medical Research Council, 2013), there is strong evidence linking higher dietary fiber and whole‐grain consumption to reduced chronic disease risk, so these two attributes serve as priorities for sorghum food innovation. Formulations need to incorporate higher levels of whole‐grain flour, whereby the starchy endosperm, germ, and bran are present in the same relative proportions as they exist in the intact kernel (Kissock et al., 2021). Next, processing should consider attributes of lower rates of starch digestibility, less gelatinization of starch granules, and lower glycemic index rankings, all of which have been shown to attenuate postprandial blood glucose levels, a risk factor in metabolic syndrome. Finally, the preservation of polyphenolic compounds (delivering antioxidant potential), which may help mitigate oxidative processes implicated in aging and disease pathogenesis, is an emerging area well worthy of processing considerations.

Case studies of sorghum research help to inform developments. For example, the previously discussed human clinical trials by Poquette et al. (2014), Stefoska‐Needham et al. (2016), and Khan et al. (2015) showcase how different processing applications have impacts at both the food level and in vivo. Importantly, these three studies examined sorghum as a whole food, after undergoing processing, whereby the physicochemical properties of the test foods were also characterized. This enabled researchers to more accurately link observed clinical effects to components and functions within the sorghum grain and the sorghum food matrix, which by extension also helped to elucidate the potential impacts of processing methods. Additionally, the test foods represented examples of modern food formats, that is, muffins, ready‐to‐eat cereal biscuits, and pasta, likely to be appealing to Western consumers.

3.1. Case Study 1: Whole‐grain muffins

Milling is typically used to produce sorghum flour needed to make such products as bread, bakery products, and pasta/noodles (Ari Akin et al. 2022; Miller Jones et al., 2015). Through this process, grains are crushed into fine particles constituting a flour product, which is in turn subjected to some form of treatment, typically involving the addition of water followed by heat, such as baking (Slavin et al., 2000). Poquette et al. (2014) successfully produced whole‐grain sorghum muffins (50 g of total starch per serving) using whole‐grain sorghum flour, high in RS, low in rapidly digestible starches (RDS), and according to a relatively simple domestic recipe. These characteristics were preserved in the end product, despite the thermal treatment, and in proportions superior to a wheat muffin control. In relation to impacts on health effects, the researchers demonstrated decreased glucose and insulin responses in healthy adults.

Thermal processing of sorghum grains has been explored extensively in the literature, especially in the pursuit of desirable new sorghum product developments. At a food level, the impact of thermal processing on health‐protective processes has been variable. For example, boiling whole‐grain sorghum in water for a period of 15 minutes was shown to reduce the total polyphenolic content by 79% (Towo et al., 2003). Soaking followed by steaming sorghum grain was also shown to significantly reduce phytochemical content (Wu et al., 2013). Extrusion cooking, which combines mixing, shearing, heat, high pressure, and chemical reactions to cook, shape, and texturize foods, was also shown to reduce phytochemical components, notably total phenols (Dlamini et al., 2007). On the other hand, Anunciacao et al. (2019) successfully produced an extruded sorghum whole‐grain breakfast cereal, higher in 3‐DXAs and phenolic contents than a wheat control, and with high antioxidant capacity. From a sensory perspective, consumers preferred the sorghum breakfast over the wheat counterpart.

3.2. Case Study 2: Whole‐grain sorghum breakfast biscuits

Stefoska‐Needham et al. (2016) produced three different whole‐grain sorghum biscuits (from red, brown, and white sorghum grains) to test satiety‐enhancing effects in healthy adults, as discussed previously in this review. As for most foods, multiple processing steps involving different treatment methods were taken to produce the biscuits: (i) steaming whole sorghum grains in a rotating pressure vessel; (ii) air drying the cooked grains; (iii) passing the dried grains through a flaking mill to achieve a thickness of 0.1 mm; (iv) pressing the moist flakes into a biscuit shaped mold; and (v) oven baking. Postprocessing characterization indicated that the red and brown sorghum biscuits had the highest polyphenolic levels, due to the respective high anthocyanin and tannin contents previously reported for these varieties (Awika & Rooney, 2004). The red and brown sorghum biscuits exhibited significantly higher total antioxidant capacity, compared to the white sorghum and wheat biscuits. Despite these differences, the starch profiling studies indicated minimal differences in RDS, SDS, and RS between the biscuits. From a clinical perspective, the sorghum biscuits had more favorable impacts on subjective satiety sensations, compared to the wheat control, with the red sorghum biscuit having the most favorable impact on levels of satiety‐enhancing hormones. Glucose responses did not differ between all biscuits and were relatively high, despite the differing polyphenolic and fiber profiles. Subsequent scanning electron microscopy showed a consistent degree of starch gelatinization across all biscuits, likely resulting from the thermal processing. This result exemplifies the effect of processing on starch gelatinization, and in turn its impact on a food's glycemic index and subsequent glucose responses in vivo. Sorghum starches have been shown to have high gelatinization temperatures, up to 81°C (Akingbala et al., 1988), although the degree of gelatinization cannot necessarily predict postprandial effects, such as digestibility and glycemic responses (Parada & Aguilera, 2011). Rather, the postprandial effects are more likely to be influenced by factors such as the amylose to amylopectin ratio, their distribution within the starch granule, additional breakdown of other polymer molecules, and postprocessing conditions, including methods of preparation (Parada & Aguilera, 2011). Overall, the observed satiety actions in the sorghum biscuits appeared to be unrelated to glucose response and to starch profile as originally postulated, and it was purported that polyphenol interactions and dietary fiber may have played a role, or likely the synergic interactions of different components of the whole food, as explained by the concept of food synergy (Jacobs et al., 2009).

This case study focused on a particular product that was useful from the commercialization perspective in a Western country. Aside from flaking, grains used to produce other types of ready‐to‐eat breakfast cereals and snacks may be extruded, puffed, and baked (Perdon et al., 2020; Thielecke et al., 2021). Feasibly, sorghum grain can be treated using the same methods, in addition to being popped, in a similar manner used to produce popcorn (Castro‐Campos et al., 2021). In other parts of the world, such as Africa and Asia, fermentation is used to make traditional forms of sorghum‐based bread and dough‐based products, including flatbreads, sourdough bread, dumplings, porridges, and gruels (extensively reviewed by Taylor & Duodu, 2015). Typically, these types of dough are fermented by lactic acid bacteria and/or yeasts. Studies implicate both enzymatic activity and microbial metabolic activity in the reduction of the phenolic content of the fermented end‐products (Babatola et al., 2021; Taylor & Duodu, 2015). Towo et al. (2006) showed that fermentation in combination with added enzymes, produced a significant reduction in the total phenol content of sorghum gruels. There is potential for sorghum‐based food products to deliver probiotic and prebiotic components through regular consumption; however; research in this area is limited, especially for modern food formats.

3.3. Case Study 3: Sorghum pasta

Healthy food product development necessitates collaboration between different disciplines, such as food science and nutrition, and dietetics (Stefoska‐Needham & Tapsell, 2020). This is exemplified in research conducted by Khan et al. (2013). In this study, new dry pasta products were produced by incorporating red or white sorghum flour into wheat flour. The uncooked sorghum‐containing pasta products showed an increase in bound phenolic acids, total phenolic content, antioxidant capacity, and RS, compared to a wheat‐based control. However, the process of cooking (i.e., boiling pasta in water) led to a decrease in the levels of free phenolic acids, anthocyanins, and total phenolic contents, but an increase in bound phenolics. The RS content was not altered. These results highlight the potential impact of processing at the food level; however, to elucidate the impact on health‐related outcomes, testing in humans was required. This was done in a follow‐up randomized controlled trial (Khan et al., 2015), whereby the cooked sorghum‐containing pasta (30% sorghum) resulted in enhanced plasma polyphenol levels, antioxidant capacity, and improved markers of oxidative stress in healthy people. The process of boiling the sorghum pasta products may have altered the levels of desirable components in the final cooked product, but not to the degree that health‐related effects were unattainable. Without the follow‐up human research, the full impact of processing on sorghum pasta could not have been completely elucidated just from the explorations at the food level.

The case studies presented highlight important considerations for the production of a health‐protective sorghum food, previously articulated by Johnson et al. (2019). Firstly, it is imperative to select the optimal sorghum varieties that contain the specific nutrients and food components involved in mechanisms associated with the target health effect (e.g., using red sorghum grain to deliver higher levels of polyphenols with greater antioxidant potential). The formulation or recipe of the sorghum food product must also be carefully considered. This ensures the desired nutritional and bioactive composition of the food is attained, and by extension, the target physiological response (e.g., using whole‐grain ingredients to produce a lower glycemic index sorghum food that may ameliorate glucose and insulin responses). Due consideration should also be given to the processing methods used to ensure that the potential health‐promoting effects of sorghum are preserved in the final products. From a research perspective, it is important to acknowledge that testing single ingredients is less informative for the impact of processing on health effects than testing the effects of the whole sorghum food as intended for consumption. Cross‐disciplinary collaboration, enabling opportunities for shared expertise, is needed to successfully achieve this.

4. CONCLUSIONS

Research involving the consumption of sorghum products has shown promise in improving metabolic indicators associated with chronic disease. These include blood glucose levels, oxidative stress markers, and acute satiety sensations linked to appetite regulation. There is also experimental evidence for beneficial cell‐mediated immune responses, including antioxidant and anti‐inflammatory effects. However, the complete range of health benefits from sorghum consumption remains to be fully explored. To gain a comprehensive understanding, further human research is warranted, including investigations involving the emerging area of gut microbiota. Consistent results from clinical trials are needed to build the highest level of evidence. This can be extended with investigations involving people with active disease profiles. Food‐based research elucidating the mechanisms of action should be included to ascribe clinical effects more accurately to components within different sorghum‐based foods. More food product innovation is required globally in order to extend the range of sorghum products available to consumers. This must be done in consideration of food processing methods to ensure the potential health‐promoting effects of sorghum are retained in end products. Alongside the importance of nutritive value, sorghum foods associated with health benefits must have high sensory acceptance for consumers to select them and eat them regularly as part of their usual diet. Overall, the current evidence for the protective health effects of sorghum whole‐grain consumption supports sorghum's position as a valuable human food source.

AUTHOR CONTRIBUTIONS

Anita Stefoska‐Needham: Conceptualization; writing—review and editing; writing—original draft.

CONFLICT OF INTEREST STATEMENT

The author has no conflicts of interest to declare.

Stefoska‐Needham, A. (2024). Sorghum and health: an overview of potential protective health effects. Journal of Food Science, 89, A30–A41. 10.1111/1750-3841.16978