Although the composition of legumes depend on several factors, such as the species, variety, environmental factors, and the cooking method applied, their nutritional profile is remarkable and provides many benefits (Table 1). Legumes are an excellent source of B-group vitamins, such as folate, thiamine and riboflavin, and vitamin C (23). Minerals, including potassium, calcium, magnesium, zinc, copper and iron are present in legumes in high amounts. In contrast, legumes are low in sodium, and this is desirable considering the recent trends encouraging salt reduction (28, 53). Furthermore, legumes are rich in linoleic and oleic acid, and bioactive compounds which have functional beneficial properties (33, 34).

Legumes are further an excellent source of protein (20–45% on weight) and represent important plant-based sources of this macronutrient (23, 35). Protein quality in legumes is, however, limited by the low concentration of the essential sulphur containing amino acids: methionine, cystine and cysteine, as well as tryptophan (53–55). This weakness can be supplemented by combining legumes with grains, that introduce great amounts of sulphur containing amino acids (55). Conversely, many grains are particularly low in lysine, and the most notable category of plant-based ingredient that can complement this lack is legumes that have a high lysine content, approaching the daily recommended intake provided by about in just 100 g of lentils or peas (36).

Scientific evidence also supports the health benefits of consuming a plant-based diet and increasing the intake of legumes thanks to their nutritional characteristics (Table 1) (35). Legumes, if consumed on a regular basis, contribute to reduced risk of mortality because of their benefits against major chronic diseases: obesity, diabetes, cardiovascular diseases, and some types of cancer (37, 38, 53, 55, 56). Legumes generally can reduce cardiovascular disease risk via improvements in blood pressure, lipid profile, inflammation, blood sugar metabolism and body weight, and offer a food-based solution to decreasing risk of developing type 2 diabetes, as reported in Figure 1. Indeed, in diabetic patients’ diets, legumes help to moderate blood sugar levels after meals, improve insulin sensitivity and glycaemic control (39, 53, 57).

Part of the health benefits of legumes may also be attributed to the low amount of fat, and to the presence of different complex carbohydrates: resistant starch, hemicellulose, oligosaccharides, lignin, and dietary soluble fibre (31, 55). The non-digestible carbohydrates of legumes can pass unchanged through the stomach and small intestine until they reach the colon, where they act as “prebiotics” for the beneficial bacteria that reside there (39). The bacterial fermentation leads to the formation of short-chain fatty acids (SCFA) which can improve colon health by promoting a beneficial gut microbiome and reducing the risk of colon cancer (39, 40, 57, 58). Furthermore, slowly digestible carbohydrates, proteins and fibres from legumes can increase the feeling of satiety and therefore reduce the risk of obesity (59) (Figure 1). Data from the National Health and Nutrition Examination Survey (NHANES), highlights that adults who consumed a variety of legumes had significantly lower body weights compared with those who did not consume legumes (57).

Legumes are further an integral part of many healthy eating patterns, including the Mediterranean style of eating (57). Serra-Mayem et al. (41) in the revision of the Mediterranean food pyramid, which incorporated recent discoveries on the sustainability and environmental impact of this dietary model, recommended the daily consumption of one small legume serving. The daily consumption of legumes has also been recommended for other types of diets such as the DASH eating plan, vegetarian and vegan diets, lower glycaemic-index diets, and diets for celiac (40, 57).

The emphasis on increased consumption of food legumes is also reflected in government-issued dietary guidelines (58). With the FAO’s assistance, about 100 countries have developed food-based dietary guidelines (59). According to an evaluation of these guidelines (60) about 87% of them recommend regular inclusion of pulses in the diet, but in general terms without specifically pointing out their nutritional value or health benefits. The guidelines of about 27% of the world’s countries mention that pulses are important sources of protein as animal foods, talking about the health benefits of reducing the consumption of meats and substituting it with pulses. However, only 15% of national dietary guidelines refer to the high iron content of pulses; and 20% point to the fact that they contain high dietary fibers. In just 8% of the guidelines, health benefits like management of obesity and diabetes are discussed.

Legumes, thanks to rhizobia (nitrogen-fixing bacteria with which they live in symbiosis), can use fixed nitrogen and produce amino acids from ammonia. This is the reason why they tend to have a higher amount of protein than other plant families (61). From an agroecological point of view, legumes play an essential role in the cultivation of sustainable agriculture also through the release of high-quality organic matter into the soil, and the consequent increase in its productivity, of both intercropped crops and crops to be cultivated subsequently (Figure 1) (62–66). Intercropping and rotation of legumes with grains, or other non-legume crops, is one of the most important elements of sustainable intensification in densely populated areas, due to benefits such as increased yield, higher nitrogen use efficiency, minimization of diseases and pests, improved access to other essential elements such as phosphorus which expand soil fertility (42, 67, 68). Grains grown in rotation after pulses yield on average 1.5 tons more per hectare than those grown without pulses, equivalent to the effect of 100 kilograms of nitrogen fertilizer (62). Furthermore, increasing the organic carbon status of the soil, legumes consequently allow to reduce the use of external fertilizers and the release of greenhouse gases in the form of CO₂ and N₂O associated with them (63, 66, 68). In fact, the production and application of synthetic fertilizers in the agricultural production system are the major contributors to GHGs emissions; and N fertilization contributes 36–52% of total emissions. A confirmed by Rekling et al. (43) integrating legumes into cropping systems, rotation can reduce nitrous oxide emissions by 18 and 33% and N fertilizer use by 24 and 38% in arable and forage systems, respectively, compared to systems without legumes (Table 1). Legumes in the cropping system also improve soil physical conditions, such as aggregate stability and soil structure, while reducing bulk density and facilitating nutrient circulation by promoting water retention (Figure 1) (67, 69). Finally, thanks to the high genetic variability of legumes, it is possible to develop high-yielding, climate-resistant varieties and, through crop rotation with legumes, increase crop diversification and agrobiodiversity (70). For example, legumes enhance earthworm activity, which along with the root channel of pulses, increases soil porosity, promotes aeration, increases water-holding capacity, and percolates deeper into the subsoil (67, 69–71).

Processing, including cooking, and packaging of legumes are important steps in the supply chain that need to be investigated since they can have a significant environmental impact (44). As reported in Table 1, an interesting Swedish study (45) compared the environmental impact of domestic and imported pulses. Authors found that contribution from processing and packaging is different between pulses purchased either dry and then cooked at home and the canned one. For canned legumes, the energy use related to retorting was almost negligible when compared with energy use in production and waste management of the packaging. For pulses purchased dry and cooked at home, the energy use was 3–6 times higher than for production of the packaging. Bandekar et al. (46) conducted a Life Cycle Assessment (LCA) for different variety of legumes considering the stages of production and consumption, including cooking, and they discovered that the consumer stage dominated the environmental impacts of pulses for all varieties and scenarios. Electricity consumed during cooking was the principal driving factor for cradle-to-grave impact of pulses and for consumer stage. The authors concluded that cooking large batches of legumes and then refrigerated, could greatly reduce environmentally impact in terms of global warming potential, fossil resource scarcity, water consumption, freshwater eutrophication, and marine eutrophication.

The concept of food has also changed several times with the progress of civilization, the expansion of knowledge, the industrial revolution, and emergence of new processing and preservation techniques. In this regard, legumes have been a fundamental part of the human diet due to the advent of agriculture and the development of civilization in the Middle East, Asia, Americas and Europe particularly in Mediterranean cultures (72, 73). Since the 1950s, there has been, however, a decline in the production of legumes, due to a series of factors including the transition of the population to dietary patterns characterized by increased consumption of meat (67, 72, 74). With the rise in large-scale poultry, livestock and aquaculture production, there has been also a relative decline in the prices of foods originating from animals. This is consistent with the drop in consumption of pulses in the diets of most regions of the world (60).

The global area and total legume production increased steadily during the 2000s, especially during the 2001s (67). Nowadays, legumes share an area of around 81 million ha with production of more than 92 million tons globally (75). The global food supplies through pulses remained, however, negligible and amounts to merely ∼1.0% of the total food supply, and 1.2% of the vegan food system (67, 74). The main socio-economic limitations to legume production are the relatively low yields compared to grains, the sensitivity to biotic and abiotic stresses, and their cultivation in harsh environments (76, 77). Legume production, likewise, has been hampered by lack of varietal protection, limited availability of genomic resources (78), and unavailability of seeds suited to various environments as well as lack of knowledge of different types of legumes by farmers and governments in agricultural policy planning (74, 76, 78). There are also other constraints to the spread of legume cultivation, including lack of adequate production markets, especially considering post-harvest losses and costs (76). Such difficulties occur mainly in high-income countries, where agricultural practices and their business models dependent on high-yield intensive systems. This hinders farmers from producing legumes, because it is economically unsustainable and socially undesirable (79). It is precisely in high-income countries that there has also been a reduction in the consumption of legumes in recent years.

Common beans feed more than 300 million people linked to agricultural economies across the world (93). Common beans are mostly sold as dry beans and a small proportion as fresh pods (60). Dry bean production has increased by about 60% since 1990 to 2020, and the area harvested increased by 36% in the same period (60, 93). Regionally, Asia leads in dry bean production with about 43% of global production, followed by America (29%), and Africa (26%) (93). All common bean lines grown in the different continents are the result of a process of domestication and evolution from wild forms (Phaseolus vulgaris var. aborigines and Phaseolus vulgaris var. mexicanus) found exclusively in the Americas (94). Beans are a rich global resource of biodiversity thanks mainly to landraces that provide genetic diversity across a wide range of seed types, produced according to diverse cultural practices (93). For centuries, farmers have maintained their varieties and have exchanged their seeds with surrounding areas, mainly in local markets (54). It is, however, not always easy to know the use and name given by farmers to their old landraces. and beans have probably been selected under dissimilar criteria and pressure (54). While landraces have a high value to preserve genetic variability and possibly organoleptic qualities, the local production cannot satisfy the current demand of the food industry. Despite this, in different countries common bean landraces are still grown, especially due to their strong link with rural gastronomy (80). Among the main food crops, the common bean also shows large variations in terms of cultivation methods, growth habit - in different environments and altitudes - as well as, in terms of plant physiology and architecture, relative duration of the reproductive cycle, and maturation time (95, 96). For these reasons, common beans show a wide range of size, shape, color and maturation time, tenderness and cooking quality of the edible plant parts (54, 57, 94).

Common beans are further greatly polymorphic with several ethnic varieties existing and with characteristics and names specific to different areas, regions, and or locality (9, 96). Consumers of different countries and regions show specific preferences for various combinations of seed characteristics, cooking time, and storability. Bean classification into “commercial types” is, therefore, also used which is related to market preferences (54). According to Doma et al. (97) the main characteristics that push consumers to choose beans are nutritional value, taste/consistency and versatility in cooking. While the strongest barriers to the bean’s consumption are: (I) beans are not part of traditional diet, (II) flatulence/abdominal discomfort, (III) knowledge gap about preparation and how to include them in daily diets (58, 83, 97), (IV) changes in lifestyles and less time available for cooking, and (V) greater availability of affordable processed foods easily to prepare (98). In this regard, consumers in developed countries avoid home-cooking beans due to the long cooking time involved. By contrast, consumers in Asia, Africa, and South America typically cook legumes at home, but choosing those that are relatively easy to cook, with shorter cook time (lentils, mung bean, and black gram) (97). In fact, long cooking time is a factor that constrains the consumption of pulses; although this phenomenon can be lessened by soaking, pressure cooking and the availability in many countries of pre-cooked dishes and ready-to-eat canned legumes (60).

Common beans are a rich and a relatively inexpensive source of proteins for a large part of the world’s population, mainly in developing countries, containing from 17 to 31% protein on a dry weight basis, in accordance with its variety (99). Common beans are further used as one of the cheapest protein sources and considered as the poor man’s meat (34, 99). Compared with animal sources of protein, beans have only 4% fat, and are also an excellent source of dietary fibre, vitamins, and minerals (Table 2) (25, 33, 100). Among carbohydrates, beans also contain oligosaccharides, mainly raffinose, which have been reported to possess prebiotic properties (23, 53).

Common beans also contain numerous bioactive compounds, such as polyphenols, flavonoids, anthocyanins and carotenoids with different biological function (101). Phenolic compounds are thereby one of the most important families of phytochemicals present in beans with antioxidant and anti-inflammatory effects. They promote several benefits including reduction in the incidence of cancer, diabetes, cardiovascular diseases, and obesity. Furthermore, phenolic acids and flavan-3-ol reduce the risk of diseases in the digestive tract (102, 103).

Common bean seeds have 4–10 times more iron (Fe) than cereals such as maize, wheat and rice (104, 116). Significant variations in the iron content of staple crops exists, which has been linked to soil iron availability (Table 2) (105). In addition, Hummel et al. (100) reported that iron levels in common bean are reduced under relevant drought stress conditions, and consistent effects have recently reviewed by Losa et al. (117). In this regard, an increased research interest is in studying the bioavailability of Fe and how it is affected by food preparation approaches (106). For this issue, the International Center for Tropical Agriculture (CIAT), in consultations with nutritionists, established a breeding goal level of 94 mg/kg Fe above the value of a standard local variety to achieve 30% of average daily Fe requirement, assuming 7% bioavailability, 90% retention after cooking, and a high level of consumption of 200 g/day beans for adults and 100 g/day for children (118). In common beans, as in all plant foods, iron is found in non-haeme form, which has a lower bioavailability than haeme iron present in meat and fish. In turn, non-haeme iron can accumulate in different chemical forms, which significantly affects its absorption. Over 90% of the iron present in legumes is stored in the form of ferritin which positively affect bioavailability (Table 2) (107).

Although consumption of common bean is widely recommended for their health-promoting nutritional quality, their use, as well as other legumes, is limited by the presence of several antinutritional factors such as phytate, raffinose family oligosaccharides, trypsin inhibitors, lectins and tannins (108, 119, 120). Phytate, the salt of phytic acid, is widely distributed in the plant kingdom serving as a storage form of phosphors and minerals (121). Phytic acid acts as a strong cation chelator, reducing the bioavailability of important minerals such as iron, zinc, potassium, calcium, and magnesium (109, 122). Phytic acid can also impact on the bio-accessibility (i.e., the transfer to mixed micelles during digestion) of fat-soluble micronutrient such as vitamin D (Table 2) (110). Similar to trypsin inhibitors, lectins and tannins reduce digestion and absorption of dietary proteins by the formation of complexes that are resistant to digestive enzymes (123–126). Tannins also highly impact pancreatic lipase activity, which partly explains their negative impact on both vitamin D (110) and potassium bio-accessibility. Decreasing nutrient bioavailability, anti-nutrients have significant adverse effects on the nutritional value of foods and can become toxic when present beyond a certain amount. Therefore, reducing their concentration in foods is a major goal in human nutrition and suitable processing of these products, including legumes, it’s necessary before their consumption (127). For this purpose, numerous traditional methods and innovative techniques have been developed over the years to reduce the amount of antinutrients and improve the nutritional characteristic of legumes.

Several traditional household food-processing, preparation and cooking methods are currently applied to enhance the bioavailability of micronutrients in plant food (86). In legumes, thermal processing, soaking, puffing, milling, fermentation, and germination/malting increases the physicochemical accessibility of micronutrients, decreasing the content of antinutrients, such as phytate, or increasing the compounds that improve bioavailability (Table 2) (112, 127, 128). For example, germination and malting are the most common legume processing methods, which are responsible for increasing iron absorption (129). This is because they help to improve the content of vitamin C or decrease the level of phytic acid, while sprouting enhances the bio-accessibility of Fe due to a reduction in the tannin content (86). However, previous results showed that reducing anti-nutrient content of legumes may be insufficient to have a significant impact on fat-soluble micronutrient bio-accessibility (110).

Various genetic tools are also currently applied to increase the production and utilization of micronutrient rich foods. These tools allow to develop bean varieties with an increased density of minerals, but also decreased amounts of inhibitors, or better food absorption (109, 113). Such genetic improvement of the nutritional value can change the anti-nutritional factors in legumes. In recent decades, research mainly focused on developing approaches aimed at reducing these antinutrients to further improve important nutritional properties to sensitize consumers for their regular consumption (109). Varieties of leguminous crops with high protein content and no anti-nutritional elements have been so far already developed, which resulted, for example, in products with a better protein availability (7).

Biofortification is further a process of increasing the density and bioavailability of vitamins and minerals in a crop through plant breeding, transgenic techniques, or agronomic practices. Biofortified staple crops are a viable means of reaching rural populations who may have limited access to adequate diets or other micronutrient-enhancing interventions (130). Conventional farming can be used to ensure a greater supply of vitamins or minerals to poor populations who depend on the specific staple crop. For example, biofortification of food crops for higher micronutrient levels of Fe, zinc (Zn) and provitamin A can boost these essential nutrients in the food system of targeted regions such as East Africa, South Asia and Latin America (131). Such breeding interventions have also been applied to develop high-yield legumes with a high micronutrient content, such as Fe biofortified beans. They are designed to address Fe deficiency, one of the most common micronutrient deficiencies globally (114) which causes anemia, fatigue, increased risk of infection, and pregnancy complications (130). Unfortunately, plant-based diets found in developing countries have low Fe bioavailability containing almost exclusively non-haeme iron, often absorbed less than 10% respect to haeme iron (113, 132). Anyway, the absorption of Fe does not only depend on its form, but also on the state of Fe in the organism: in case of deficiency, its absorption-in both forms-increases (132, 133). Furthermore, the bioavailability of Fe is influenced by the presence of its inhibitors, mainly phytates, polyphenols, calcium, milk and egg proteins, and by its enhancers such as ascorbic acid. It is, therefore, clear that the diet as a whole, influences the risk of anemia (56, 133). In addition, in common beans and legumes non-heme Fe in the form of ferritin ensures protection from the chelating action of phytic acid, making it more bioavailable. This effect is maintained during cooking and digestion, because phytoferritin remains intact during these processes (56).

In rural populations, biofortified beans can improve nutrition through two main pathways, primarily in the households that produce and consume them. The first is to increase nutrient intake through increased consumption of the home-grown biofortified crop, which has a higher iron content than other available bean varieties. The second path occurs by increasing the family income available for the purchase of other nutritious foods (120). Recent studies have been, therefore, conducted for the successful breeding of common beans using classical breeding methods to accomplish a wide array of objectives. This includes increasing the adaptation of the beans to different environmental conditions, developing genetically improved cultivars and increasing resistance against various biotic and abiotic stresses (96, 111).