Cowpea

Cowpea (Vigna unguiculata (L.) Walp.): A Comprehensive Reference

1. Identity, Taxonomy, and Botanical Description

Scientific Name and Classification

Cowpea (Vigna unguiculata) is a dicotyledonous, leguminous plant belonging to the order Fabales, family Fabaceae, subfamily Faboideae, tribe Phaseoleae, subtribe Phaseolinae, genus Vigna, and section Catiang. Its full accepted scientific name is Vigna unguiculata (L.) Walp. It is an annual legume generally cultivated in dry, semiarid, and subtropical regions.

There are two botanical self-pollinated varieties of annual cowpea: the cultivated V. unguiculata var. unguiculata and the wild form V. u. var. spontanea. Scientists have further reclassified cowpea, grouping it under Vigna unguiculata subspecies unguiculata, which includes four main types (cultigroups).

Common Names

Cowpea is commonly known as southern pea, black-eye pea, crowder pea, lubia, niebe, coupe, or frijole. The English term "cowpea" refers to the species V. unguiculata as well as to all its subspecies; the plant is also known by the French names Niébé, pois à vache, cornille, dolique à œil noir, and haricot indigène. In India, it is popularly called Barbarti and lobia.

Morphology

V. unguiculata is an erect or climbing elongated herbaceous plant measuring 30–60 cm in height on average (extremes: 15–80 cm). The leaves are alternate and trifoliate with a petiole of 5–25 cm in length. The lateral leaflets are opposite and asymmetrical, whereas the central leaflet is symmetrical, oval, and often larger. The inflorescence is branchy with long peduncles topped with white, cream, yellow, mauve, or crimson flowers. The flowers, typical of leguminous plants, contain nectar which contributes to the attraction of insects.

The cowpea has the particularity that the aerial section of the plant is entirely edible. Cowpeas produce long, hanging pods, which are sometimes harvested while immature and eaten as a vegetable, especially in Asia. In Asia, cowpea has evolved into a vegetable form known as yardlong bean.

Geographic Distribution

Grown on more than 11.5 million hectares in Africa, Southeast Asia, and some countries in the Americas, cowpea is the third most important pulse worldwide. It is widely planted in semi-arid regions because of its ability to produce in dry and hot conditions. Today, the greatest diversity of cowpea can be found in West Africa in the savanna regions of Burkina Faso, Ghana, Togo, Benin, Niger, Nigeria, and Cameroon.

2. Historical and Traditional Use

Origins and Early History

Cowpea was domesticated in Africa, likely in both West and East Africa, before 2500 BCE, and by 400 BCE was long established in all the modern major production regions of the Old World, including sub-Saharan Africa, the Mediterranean Basin, India, and Southeast Asia. The history of cowpea dates to ancient West African cereal farming, 5 to 6 thousand years ago, where it was closely associated with the cultivation of sorghum and pearl millet.

Cowpea was introduced to Europe probably around 300 BCE and to India around 200 BCE. Further spread occurred as part of the Columbian Exchange, which brought African germplasm to the Caribbean, the southeastern United States, and South America, and Mediterranean germplasm to Cuba, the southwestern United States, and Northwest Mexico.

Traditional Food Uses by Culture

In West Africa, cowpea seeds are ground into flour and mixed with onions and spices to make cakes that are either deep-fried ("akara balls") or steamed ("moin moin") as a snack. Cowpea flour can also be processed into crackers and baby foods, as is the case in Senegal, Ghana, and Benin. In Africa, the dry seed is commonly ground and consumed in several traditional African dishes, such as porridge, bread, and as a food for weaning children, or processed into fritters.

African methods of cooking cowpeas — such as using boiled whole peas combined with rice, added to stews, or served alone — were transported to the New World by enslaved Africans. There are records of its use in Jamaica as early as 1675; it has documented use in Florida in 1700 and in North Carolina in 1714.

Besides the seeds, the leaves and pods of cowpea are eaten as vegetables, served boiled or fried. Many people dry the leaves in the sun to preserve them so they can be eaten during the dry season when food is scarce. Cooked cowpea pods are more typical of Asian cuisine than African cuisine.

Traditional Medicinal Use

Traditionally, different potentials of cowpea have been reported for the management of various conditions including schistosomiasis, stubborn boils, common cold, tooth ailments, swelling, infections, epilepsy, chest pain, constipation, dysmenorrhea, tachycardia, and painful menstruation.

Medicinally, cowpea is used in traditional remedies for ailments such as fever, digestive issues, and liver conditions. The seeds, roots, and leaves are employed to treat burns. Various parts of the cowpea are used medicinally. The leaves and seeds are applied to skin infections as a poultice, the leaves are chewed to relieve toothache, and powdered carbonized seeds are applied to insect stings.

In China, the seeds do not appear to be used as a medicinal drug, in contrast to the seedless pods and the plant itself. Various societies across the world have used V. unguiculata as both food and medicine. Apart from being a foodstuff, the plant's leaves, seeds, and pods have been used to address microbial infections, diabetes, various forms of inflammation, digestive problems, and cardiovascular disease.

Cowpea is a useful plant that helps large numbers of people in tropical and subtropical nations, especially in Africa — including Nigeria, Burkina Faso, Kenya, Niger, Uganda, Tanzania, Ghana, Senegal, and Togo — and in Asia, including India, Pakistan, Sri Lanka, Burma, Bangladesh, Thailand, China, Malaysia, and Nepal — for the improvement of health and fulfilment of nutritional needs.

3. Nutritional Composition

Macronutrients

Cowpea grain contains, on average, 23–25% protein and 50–67% carbohydrate. High protein and carbohydrate contents with relatively low fat content and a complementary amino acid pattern to that of cereal grains make cowpea an important nutritional food in the human diet. As with most legumes, the amino acid profile of cowpea complements cereal grains. Results in one study showed five cowpea cultivars to be high in protein (18.0–28.7%) and carbohydrates (54.9–66.0%) and low in fat (0.6–3.7%).

The total dietary fiber content of cowpea has been reported to range from 12.00 ± 0.15 to 14.80 ± 0.20 g/100 g and similarly from 13.60 ± 0.15 to 15.99 ± 0.49 g/100 g in other studies. Soluble and insoluble fiber ratio in cooked cowpeas is approximately 1:3.2.

Protein Fractions and Amino Acids

Globulins constitute the major seed proteins (493.2–573.3 g/kg total seed protein), followed by albumins (201.0–248.0 g/kg), basic glutelins (119.1–154.3 g/kg), acid glutelins (82.4–92.3 g/kg), and prolamins (13.2–20.2 g/kg). Amino acid composition shows common prevalence of glutamine/glutamic acid, asparagine/aspartic acid, and phenylalanine plus tyrosine; methionine plus cysteine contents were low across all cultivars.

Vitamins and Minerals

Cowpea is an important source of specific vitamins and minerals. It is an especially excellent source of thiamin and folate, where 100 g of cowpea provides 57% and over 150% of the daily requirement, respectively, as part of a 2000-kcal diet. Similarly, 100 g provides 41–76% of the daily requirement for phosphorus, magnesium, iron, copper, and manganese.

Consumption of traditional cowpea-based dishes in one West African study allowed for coverage of 42% of the recommended nutrient intake (RNI) of dietary fibre, and the contribution to the RNI of magnesium (37%), folate (30%), protein (26%), zinc (18%), and potassium (17%) was also notable.

Carotenoids

Lutein (124.6 mg/100 g) and all-trans-beta-carotene (92.6 mg/100 g) levels were highest in specific cowpea cultivars analyzed for leaf composition. Carotenoids are well represented in cowpea leaves and contribute to their nutritional density as a leafy vegetable.

4. Key Phytochemical Constituents and Active Compounds

Overview of Isolated Compounds

Compounds isolated from various parts of the cowpea plant include flavonoids, steroids, alkaloids, phenolic compounds, saponins, fatty acids, tannins, carbohydrates, vitamins, amino acids, carotenoids, and fibers.

Polyphenols: Phenolic Acids and Flavonoids

The major polyphenols common to all cowpea varieties are phenolic acid derivatives (148–1,176 µg/g) and flavonol glycosides (27–1,060 µg/g). Some varieties also contain anthocyanins (875–3,860 µg/g) and/or flavan-3-ols (2,155–6,297 µg/g). The flavan-3-ols (tannins) are dominated by monomers, mostly catechin-7-O-glucoside.

HPLC-MS analysis of crude methanolic extracts of cowpea has resulted in the identification of flavonols such as quercetin and kaempferol, and phenolic acids such as p-coumaric acid, protocatechuic acid, and gallic acids. Other common phenolic compounds identified include gentisic acid, ferulic acid, and quercetin.

Pigmented seed varieties of cowpea possess higher total phenolic content, total flavonoid content, ferric reduction ability, and anti-lipid peroxidation activities than colourless varieties.

Bioactive Peptides

Research has found that cowpea peptides mimic the action of insulin and induce protein kinase B (Akt) phosphorylation in the skeletal muscles of rats via activation of the insulin-signaling cascade. Akt acts as a signaling molecule in the insulin-signaling pathway and is required to induce cellular glucose transport.

In studies by Guang and Phillips and Leon et al., hydrolysates of cowpea protein (peptides) were reported to effectively inhibit angiotensin-converting enzyme I (ACE-I) activity compared to the unhydrolysed protein.

Phytosterols

Cowpeas include phytosterols, which are steroid molecules extremely beneficial in preserving normal cholesterol levels in the body.

Resistant Starch

The low glycemic index of cowpea is attributed to the action of resistant starch and dietary fiber, which attenuate insulin responses and reduce hunger. Cowpea's slowly digestible starch also adds to its health benefits.

5. Mechanisms of Action

Antioxidant Mechanisms

Research on Burkina Faso cowpea cultivars indicates that they are rich in phenolic compounds and have significant antioxidant and anti-lipid peroxidation activities. Consumption of cowpea, particularly of colored seed varieties, is considered potentially beneficial for the prevention of chronic human diseases. Cowpea appears to have a unique profile of some polyphenols, especially the flavonols and flavan-3-ols, which implies that they may provide unique bioactive properties that complement other food commodities.

Antidiabetic Mechanisms

Phenolic compounds in cowpea exhibit antidiabetic activity by inhibiting α-amylase and through lipid oxidation inhibition. High inhibition (>50%) of α-glucosidase and α-amylase activities has been demonstrated by cowpea leaf extracts at concentrations of 50 and 25 mg/mL, and cowpea cultivars demonstrated the highest gene expression levels of GLUT4 regulation in C2C12 skeletal muscle cells, similar to insulin.

Antihypertensive Mechanisms

Among the mechanisms proposed in the prevention of chronic diseases, the most substantiated are attributed to the presence of soluble and insoluble dietary fiber, phytochemicals, and proteins and peptides in cowpea. The ACE-inhibitory activity of cowpea-derived peptides represents a plausible antihypertensive mechanism, though this has primarily been studied in vitro.

Anticancer Mechanisms (Preclinical)

In vitro, a cowpea phenolic extract at a concentration of 100 mg GAE/L inhibited 65% of the proliferation of hormone-dependent mammary (MCF-7) cancer cells. This result is preclinical only and does not establish clinical anticancer efficacy.

6. Scientific Evidence by Health Area

6.1 Blood Glucose Regulation and Diabetes

Consumption of cowpea legumes is associated with reduced risk of type 2 diabetes mellitus. Cowpea flour contains 24.1% protein, 14.1% dietary fiber, and has a reported low glycemic index of 46.64. Foods with a glycemic index ≤55 are classified as low-GI according to standard nutritional classifications.

A 2025 clinical trial registered with the Brazilian Clinical Trials Registry (ReBEC, number RBR-7ntftdv) examined iron-biofortified cowpea varieties in healthy adults. Iron-biofortified (BRS Aracê, BRS Tumucumaque, and BRS Xiquexique) and conventional (BRS Pajeú) cowpeas were cooked and their chemical composition was analyzed. Eutrophic adults (n=11) consumed each cowpea and control glucose, and post-prandial glucose and appetite responses were obtained over 120 minutes. Cowpeas showed low glycemic index and glycemic load; one variety (Pajeú) induced the lowest "hunger sensation" and higher "satiety sensation"; and biofortified cowpeas reduced the activation of inflammation markers in RAW 264.7 cells. The small sample size (n=11) limits the generalizability of these findings.

In vitro data further supports the antidiabetic potential: high inhibition (>50%) of α-glucosidase and α-amylase was shown by leaf extracts, and cowpea cultivars demonstrated the highest gene expression levels of GLUT4 in C2C12 skeletal muscle cells, similar to insulin. A positive correlation existed between the phenolic components and the inhibitory effect on antidiabetic enzymes and FRAP activity. Overall, the clinical human evidence remains preliminary and largely limited to small trials; further large-scale randomized controlled trials are needed.

6.2 Cardiovascular Health and Lipid Metabolism

After analyzing a large volume of experimental data, Sreerama et al. demonstrated antidiabetic and cardiovascular protective effects of phenolic extracts from cowpea. According to recommendations of the Central Council for Research in Ayurveda and Siddha, cowpeas are good sources of soluble fiber and protein, which help maintain cholesterol levels in the blood.

Cowpea has gained more attention recently from consumers and researchers worldwide due to its potential health-beneficial properties including anti-diabetic, anti-cancer, anti-hyperlipidemic, anti-inflammatory, and anti-hypertensive properties. However, studies on the anticancer and anti-inflammatory properties of cowpea have produced conflicting results. The cardiovascular evidence is largely derived from epidemiological observations, in vitro experiments, and animal models; robust prospective human clinical trials specific to cowpea are lacking.

6.3 Antioxidant Activity

Total phenolic content (TPC), total flavonoid content (TFC), and radical scavenging capacity (by DPPH) have been measured across cowpea genotypes. Seed coat extracts showed higher contents of phenolics (291.0 ± 4.6 mgGAE/g) and flavonoids (83.5 ± 1.1 mgCE/g) and stronger radical scavenging capacity (50.4 ± 0.7 µmolTE/g) than leaf extracts. These are in vitro measurements only and do not directly translate to in vivo antioxidant outcomes in humans.

6.4 Appetite, Satiety, and Body Weight

The low glycemic index of cowpea is attributed to the action of resistant starch and dietary fiber, which attenuate insulin responses and reduce hunger. In the 2025 clinical trial cited above, one cowpea variety induced the lowest hunger sensation and higher satiety sensation among tested subjects. Evidence in this area consists of one small clinical trial and mechanistic hypotheses; it is preliminary.

6.5 Protein Nutrition and Child Growth

In terms of addressing nutritional security, cowpea is considered suitable for addressing protein-energy malnutrition and for formulating blends for baby foods. Sprouting of legumes enhances the bioavailability and digestibility of nutrients and therefore plays an important role in human nutrition. Clinical evidence on the specific use of cowpea for addressing child malnutrition exists at the protocol level in some settings but is not yet fully reported in major systematic reviews.

6.6 Gut Health and Digestive Function

Cowpea improves digestion and increases intestinal mobility and the bulk of feces. Its insoluble fiber component makes it a candidate for supporting colonic health. The evidence for this is largely indirect, based on fiber content measurements, and lacks dedicated human trials focused specifically on cowpea and gut microbiome outcomes.

6.7 Antimicrobial Activity

The bioactive compounds found in cowpea — including alkaloids, terpenoids, polyphenols, and flavonoids — are presumed to be responsible for the plant's antimicrobial activity. This evidence is based on preclinical and in vitro studies only; no robust human trials evaluating cowpea's antimicrobial efficacy in clinical infection contexts have been identified.

7. Forms, Preparations, and Dosages Reported in Studies

Common Food and Supplement Forms

The cowpea's whole grains, decoctions, hulls, and leaves are prepared and used for human consumption. Common preparations include:

• Whole dried seeds — boiled or pressure-cooked, the most common form globally.
• Cowpea flour — used in bread, fritters (akara), steamed cakes (moin moin), crackers, and weaning foods.
• Sprouted seeds — sprouting enhances the bioavailability and digestibility of nutrients and plays an important role in human nutrition.
• Fermented preparations — natural fermentation improved apparent and true fecal digestibility of numerous indispensable amino acids, explained by diminished concentration of protease inhibitors, as fermentation almost eliminated trypsin inhibitor activity and lowered phytic acid and polyphenol content.
• Immature pods and leaves — consumed as fresh vegetables.
• Decoctions and poultices — used in traditional medicine.

Dosages in Studies

Human clinical trial data using cowpea in standardized supplement form is limited. The dosages found in the available clinical literature are as food-based interventions:

• In the 2025 Brazilian clinical trial, eutrophic adults (n=11) consumed cooked iron-biofortified and conventional cowpea preparations, with post-prandial glucose and appetite responses measured over 120 minutes.
• In vitro antidiabetic assays have used leaf extracts at concentrations of 50 and 25 mg/mL.
• In vitro anticancer assays used a phenolic extract at a concentration of 100 mg GAE/L.

No standardized therapeutic dosage for cowpea as a dietary supplement has been established or formally endorsed by any regulatory or pharmacopoeial authority identified in available literature.

8. Anti-Nutritional Factors and Safety Considerations

Documented Anti-Nutritional Factors

Phytochemicals that may be nutritionally deleterious include lectins, trypsin inhibitors, tannins, proanthocyanidins, phytic acid, haemagglutinins, cyanogenic glucosides, oxalic acid, dihydroxyphenylalanine, and saponins found in cowpea seeds and leaves.

The presence of anti-nutritional factors (ANFs) including phytates, alpha-galactosides such as raffinose and stachyose, and tannins significantly reduces micronutrient bioavailability and creates some problems of acceptability in using cowpea and other legumes. Phytates found in cowpea seeds can impair the bioaccessibility of vital minerals and proteins by producing phytate–protein and phytate–mineral complexes. Unprocessed cowpeas have been reported to contain phytic acid at approximately 836 mg/100 g.

Cowpea dry seeds contain phytic acid/phytates, flavonoids, and tannins. Phytic acid, classified as an antinutrient, chelates essential minerals (calcium, iron, and zinc), thereby making them unavailable.

Effects of Processing on Anti-Nutritional Factors

Pressure cooking and boiling result in significant destruction of anti-nutrients like phytates, tannins, and trypsin inhibitors. In vitro protein digestibility was highest (93.9%) with 3-minute pressure cooking, followed by 15-minute boiling (91.0%).

Natural fermentation improved apparent and true fecal digestibility of numerous indispensable amino acids, explained by diminished concentration of protease inhibitors; fermentation almost eliminated trypsin inhibitor activity and lowered phytic acid and polyphenol content. Heat treatment procedures have proved adequate for reducing the activity of several secondary plant metabolites, especially heat-labile compounds (protease inhibitors and lectins).

Flatulence-Causing Oligosaccharides

The alpha-galactosides present in cowpea (raffinose and stachyose) are fermented by colonic bacteria and are a well-documented cause of flatulence in consumers of legumes. Soaking and cooking substantially reduce these compounds, though they are not fully eliminated by standard household methods.

Mineral Chelation and Micronutrient Bioavailability

Some nutritional constraints in cowpea reduce mineral bioavailability and absorption, protein and starch digestibility, causing both macronutrient and micronutrient issues among populations that consume it as a staple food. Adequate processing — including soaking, sprouting, boiling, fermentation, or autoclaving — can substantially mitigate these effects.

Allergenic Potential

Cowpea belongs to the Fabaceae (legume) family, and like other members of this family, it has the potential to cause allergic reactions in individuals sensitive to legumes. However, specific clinical data on cowpea allergy prevalence and severity was not identified in the sources reviewed for this article.

9. Body Systems and Health Areas of Association

• Metabolic / Endocrine: Blood glucose regulation (low GI, α-glucosidase and α-amylase inhibition, GLUT4 upregulation); lipid metabolism (phytosterols, flavonoids).
• Cardiovascular: Potential ACE-inhibitory activity via bioactive peptides; cholesterol modulation via dietary fiber and phytosterols.
• Gastrointestinal: Dietary fiber supporting bowel motility, colonic bulk, and potential colon health; fermentable fiber for gut microbiota (also a source of flatulence).
• Nutritional / Hematological: High iron, folate, and zinc content relevant to anemia prevention; protein source for protein-energy malnutrition.
• Antioxidant / Anti-inflammatory: Rich phenolic and flavonoid profile with demonstrated in vitro antioxidant and anti-lipid peroxidation activity.
• Oncology (preclinical only): In vitro inhibition of MCF-7 breast cancer cell proliferation by phenolic extracts.
• Reproductive / Developmental: High folate content relevant to neural tube defect prevention in pregnancy.

10. Evidence Strength Summary

Research to demonstrate direct health-promoting effects of cowpea bioactives in humans is still needed. The evidence base for cowpea's health effects can be summarized as follows:

• Strong (observational/compositional): Nutrient density — protein, folate, fiber, minerals — is well established by multiple analytical studies.
• Moderate (preclinical and limited clinical): Low glycemic index, with one small registered clinical trial (n=11) confirming low GI and glycemic load in humans.
• Preliminary (in vitro and animal models only): Antioxidant, antidiabetic enzyme inhibition, ACE inhibition, and anticancer properties — all demonstrated primarily in cell or animal models, not confirmed in human trials.
• Conflicting or insufficient: Anti-inflammatory and anticancer evidence in humans; studies on the anticancer and anti-inflammatory properties of cowpea have produced conflicting results.

References

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