Description

Vigna unguiculata (L.) Walp., commonly known as cowpea, black-eyed pea, or southern pea, is a species of flowering plant in the bean family Fabaceae (Leguminosae), the same family as beans, peas, and peanuts. The genus name Vigna honors Domenico Vigna, a 17th-century Italian botanist, while the species epithet unguiculata means “with a small claw,” referring to the shape of the flower petals.

Origin and Distribution: Cowpea is native to tropical Africa, with the greatest genetic diversity found in the savanna regions of West Africa, particularly Burkina Faso, Ghana, Benin, Niger, Nigeria, and Cameroon. It is the most important grain legume in tropical Africa and is widely cultivated across the continent, as well as in Asia (India, China, Southeast Asia), the Americas, and the Mediterranean region. The plant is often called “poor man’s meat” in developing nations due to its high protein content and affordability.

Morphology: Cowpea is an annual herbaceous plant. It exhibits considerable variation in growth habit, ranging from erect and bushy to prostrate and trailing, with stems that can be twining or climbing. The plant typically reaches 15–80 cm in height, though climbing varieties can be much longer.

Leaves: The leaves are alternate and compound (trifoliate), consisting of three leaflets. The leaflets are ovate to hastate (arrowhead-shaped), measuring 5–15 cm in length and 3–11 cm in width. The central leaflet is generally largest, and the leaflets are smooth (glabrous) or nearly so. The petiole (leaf stalk) ranges from 2.5 to 12.5 cm in length.

Flowers: The inflorescence is an axillary raceme (a cluster of flowers along an unbranched stalk), typically bearing 2–6 flowers at the tip of a peduncle (flower stalk) that can reach 15–30 cm in length . The flowers are typical of the Fabaceae family, with a papilionaceous (butterfly-like) corolla. They are usually white, cream, pale yellow, or pale purple, often with a distinctive purple or maroon blotch at the base of the standard petal. The flowers are primarily self-pollinating.

Fruit (Pod): The fruit is a linear, cylindrical pod that is typically curved or sickle-shaped, measuring 7.5–70 cm (or even up to 90 cm in yard-long bean varieties) in length and 6–10 mm in width. Pods are borne singly or in pairs and are usually green, turning straw-colored or brown when mature. They contain 10–20 seeds.

Seeds: The seeds are typically kidney-shaped (reniform) or oblong, measuring 6–12 mm in length . They exhibit a remarkable range of colors, including white, cream, brown, red, black, and various mottled patterns. The most recognizable variety is the black-eyed pea, which is cream-colored with a distinct black “eye” or hilum. The seed coat is smooth, firm, and lustrous.

Subspecies and Cultivar Groups: Vigna unguiculata is divided into several cultivar groups based on use:

• Unguiculata Group: Grown for dry grain (standard cowpea)
• Sesquipedalis Group: The yard-long bean or asparagus bean, grown for its very long (up to 90 cm), tender pods, which are eaten as a vegetable
• Biflora Group: Grown for its green pods and seeds as well as for forage
• Textilis Group: A small group cultivated only in Nigeria, grown for the long fibres (up to 60–100 cm) extracted from the peduncles

 Common names (including Nigerian)

• English: Cowpea, Black-eyed pea, Southern pea, Crowder pea, Field pea, Yard-long bean (for the Sesquipedalis group)
• French: Niébé, Haricot à l’œil noir
• Hausa: Wake
• Yoruba: Ewa, Ewa funfun (white beans), Ewa oloyin (sweet beans)
• Igbo: Agwa, Okwolo
• General Nigerian English: Cowpea, Black-eyed peas, Beans
• India (Hindi): Lobia, Chowli
• Pakistan (Urdu): Lobia
• China (Mandarin): Jiāngdòu (豇豆)
• South Africa: Akkerboon
• Brazil: Feijão-caupi

 Health Benefits

Vigna unguiculata is not only a vital food crop but also a plant with significant medicinal properties. A 2024 comprehensive review in Heliyon concluded that the plant possesses “strong pharmacological, nutritious and phytochemical potential” and is strongly recommended for additional clinical investigations.

1. Nutritional Composition (“Poor Man’s Meat”)

Cowpea is one of the most nutritious legumes and serves as an affordable source of high-quality protein, earning its nickname “poor man’s meat” in developing nations. Protein helps Build and repair tissues, Support muscle growth, Maintain healthy organs, and Produce enzymes and hormones

Proximate Composition (per 100g of seeds):

• Carbohydrates: 55–66%
• Protein: 18–30%
• Fat: 1–3%
• Dietary Fiber: 6–10%

Mineral Content (per 100g):

• Iron (Fe): 4–8 mg
• Calcium (Ca): 50–100 mg
• Potassium (K): 300–500 mg
• Phosphorus (P): 200–400 mg
• Magnesium (Mg)  100–200 mg

These nutrients support Bone development, Blood formation, Immune function, and Energy metabolism

Vitamin Content:

Vitamin A: Beta-carotene (in leaves)

• Folate (B9): High
• Thiamine (B1): Moderate
• Riboflavin (B2): Moderate

Amino Acid Profile: Cowpea is rich in essential amino acids, particularly lysine, which is often lacking in cereal grains. This makes cowpea an excellent complement to cereal-based diets. The combination of cowpeas with rice, maize, or millet provides a complete protein profile.

• Antioxidant Properties

Cowpea contains numerous bioactive compounds with potent antioxidant activity, including flavonoids, phenolic compounds, saponins, tannins, carotenoids, and vitamins. These compounds neutralize harmful free radicals, reduce oxidative stress, and help prevent chronic diseases.

The plant’s antioxidant potential is attributed to isolated compounds such as quercetin, kaempferol, catechin, and various phenolic acids .

• Cardiovascular and Cholesterol-Lowering Effects

Cowpea has demonstrated significant hypocholesterolemic and antiatherogenic effects (cholesterol-lowering and artery-protecting effects) in scientific studies.

Mechanisms:

• The high dietary fiber content binds bile acids and promotes their excretion, forcing the body to use cholesterol to produce more bile acids.
• The presence of plant sterols and saponins interferes with cholesterol absorption in the gut.
• The antioxidant compounds reduce the oxidation of LDL (“bad”) cholesterol, a key step in the development of atherosclerosis.
• Antidiabetic (Blood Sugar Regulation) Properties

Cowpea exhibits antidiabetic activity and has been traditionally used for managing diabetes in several cultures.

Key findings:

• The high soluble fiber content slows the absorption of carbohydrates and sugars, preventing rapid spikes in blood glucose levels.
• Certain bioactive compounds in cowpea may influence insulin sensitivity and glucose metabolism.
• In the Philippines, yard-long beans (Vigna unguiculata subsp. sesquipedalis) are specifically used as a traditional cure for diabetics.
• Digestive Health

Cowpea is rich in dietary fiber, which promotes regular bowel movements, prevents constipation, and supports a healthy gut microbiome. Traditional medicine systems use cowpea to strengthen the stomach and treat digestive issues.

Antidiarrheal properties: In traditional medicine, leaf decoctions are used to treat diarrhea and dysentery.

• Antimicrobial and Antibacterial Properties

Studies have demonstrated that cowpea extracts possess significant antimicrobial and antibacterial activities against various pathogens .

Key findings:

• The leaves and seeds have shown activity against bacteria responsible for common infections.
• The plant has demonstrated antibacterial, anthelmintic (anti-parasitic), and anti-sickling properties.
• Preliminary research has even explored anti-COVID activity.
• Anti-inflammatory Properties

Cowpea has documented anti-inflammatory activity, attributed to its rich content of flavonoids, alkaloids, and phenolic compounds.

Traditional use: Leaves and seeds are used as a poultice to treat swellings, boils, and infections .

• Hematological Benefits (Anti-sickling and Thrombolytic)

Research has documented the anti-sickling potential of cowpea compounds, which may be beneficial for individuals with sickle cell disease. Additionally, the plant exhibits thrombolytic properties (capable of breaking down blood clots), supporting cardiovascular health.

• Anticancer (Antineoplastic) Properties

The phytochemicals present in cowpea, particularly the flavonoids and phenolic compounds, have demonstrated anticancer activity in laboratory studies . These compounds may help prevent the initiation and progression of certain types of cancer by:

• Neutralizing carcinogens
• Inducing apoptosis (programmed cell death) in cancer cells
• Preventing angiogenesis (blood vessel formation that feeds tumours)
• Neurobehavioral Activity

Emerging research indicates that cowpea may have neurobehavioral effects, suggesting potential applications in neurological health.

1. High Folic Acid (Folate) Content and Pregnancy Support:

Cowpeas pack an exceptionally high concentration of Vitamin B9 (folate). A single cup of cooked cowpeas provides a significant portion of the daily recommended intake, which is absolutely vital for pregnant women to prevent neural tube birth defects.

1. May Reduce Risk of Chronic Diseases

Regular consumption may contribute to reduced risk of Cardiovascular diseases, Obesity, Type 2 diabetes, and Certain inflammatory conditions

1. Traditional Medicinal Uses (African and Global Context)

Cowpea has a long history in traditional medicine across multiple continents :

Condition	Plant Part Used	Preparation Method
Diarrhea, dysentery, stomach ache	Leaves, roots	Decoction taken orally
Boils and swellings	Seeds	Ground seeds mixed with oil, applied as a poultice
Common cold	Seeds	Cooking liquor from seeds with spices consumed
Wounds	Leaves	Applied topically to promote healing
Respiratory problems (cough, colds, bronchitis)	Leaves	Boiled; vapours inhaled
Blood in urine, Schistosomiasis	Seeds (with other roots)	Cooked and consumed
Thirst	Seeds	Starch jelly used against thirst
Dental problems	Leaves	Chewed to treat dental issues
Schistosomiasis	Seeds	Cooked with roots of other herbs

Other benefits

• Livestock Feed: Cowpea is an important forage crop. The leaves, pods, and seed residues (after processing) are used as high-protein animal feed for cattle, goats, sheep, and poultry .
• Soil Improvement and Nitrogen Fixation: As a legume, cowpea forms symbiotic relationships with nitrogen-fixing bacteria (Rhizobium) in its root nodules. This process enriches soil fertility by converting atmospheric nitrogen into a form usable by plants, making cowpea an excellent cover crop and green manure in crop rotation systems .
• Erosion Control: The plant’s spreading growth habit and dense foliage help protect soil from erosion, particularly in semi-arid regions.
• Coffee Substitute: In Sudan and Ethiopia, charred cowpea seeds are sometimes used as a coffee substitute.
• Fiber Production (Nigeria): The Textilis cultivar group is grown specifically in Nigeria for the long, strong fibres extracted from its peduncles (flower stalks), which can reach 60–100 cm in length. These fibres are used for weaving and cordage.
• Natural Dye: The seed coats of certain dark-colored varieties can be used to produce natural dyes.
• Economic Importance: Nigeria is the world’s largest producer of cowpea, and the crop is a major source of income for smallholder farmers across West Africa.
• Food Security: Cowpea is drought-tolerant and can be grown in semi-arid regions where other legumes fail, making it a critical crop for food security in marginal agricultural areas .
• Sustainable Agriculture: Cowpea contributes to Crop rotation systems, Intercropping programs, and Sustainable land management
• Industrial Food Applications: Cowpea flour is used in Composite flour production, Baby foods, Protein-enriched foods, and Snack production
• Cultural Importance: Cowpea is an essential component of many traditional Nigerian foods and cultural practices.

How it is used

 Culinary uses (Nigerian and global context):

Whole Seeds (Dry Beans):

In Nigeria, cowpeas are the most widely consumed legume and are prepared in numerous ways:

• Beans Porridge (Ewa Oloyin): The most common preparation. Brown or honey beans (ewa oloyin) are boiled until soft, then mashed and cooked with palm oil, onions, peppers, and seasonings. It is often served with bread, yam, plantain, or garri.
• Boiled Beans (Ewa Aro): White or brown beans are simply boiled with salt, potash (kawun), and sometimes onions until tender. Served as a breakfast or main meal, often with bread, pap (ogi), or fried plantains.
• Beans and Plantain (Ewa Ati Ogede): Boiled beans combined with fried or boiled unripe plantains.

Milled Beans (Beans Flour):

• Moin-Moin (Bean Pudding): Ground, skin-removed beans (black-eyed peas) are blended with onions, peppers, crayfish, and palm oil (or vegetable oil). The mixture is poured into ramekins, banana leaves (ewe ogede), or cellophane bags and steamed until set. It is served as a breakfast item, snack, or side dish with pap (ogi), rice, or bread.
• Akara (Fried Bean Cakes): The same beans flour mixture as moin-moin is whipped to incorporate air, then deep-fried in palm oil or vegetable oil until golden brown. Akara is a popular breakfast item, often eaten with pap (ogi), bread, or yam, and is a staple street food.

Fresh Green Leaves:

• Efo Ewa (Cowpea Leaf Vegetable): The young, tender leaves of the cowpea plant are harvested, washed, and cooked as a leafy green vegetable, similar to spinach or ugu. They are added to soups and stews or simply boiled and sautéed with palm oil, onions, and peppers.

Immature Green Pods:

• The tender, immature pods (of the standard cowpea or the yard-long bean variety) are sliced and added to soups, stews, and stir-fries. They can also be steamed or boiled as a side dish.

Roasted Cowpea Snack: Dry cowpeas can be roasted (like groundnuts) and eaten as a crunchy, protein-rich snack.

Fermented Products: Cowpea seeds can be fermented to produce iru (locust bean substitute) or other fermented condiments, though this is less common than fermentation of African locust beans.

 Specific Nigerian Recipes

1. Akara (Fried Bean Cakes) – Popular across Nigeria
2. Ingredients (serves 4–6):
   1. 2 cups cowpea (black-eyed peas)
   1. 1 medium onion
   1. 2–3 Scotch bonnet peppers
   1. Salt to taste
   1. Vegetable oil for deep frying
3. Method:
4. Soak cowpea in water for 1–2 hours (or overnight). Peel off the skin by rubbing between palms.
5. Blend peeled beans with onion and peppers into a smooth, thick paste (add very little water).
6. Whisk the paste vigorously for 5–10 minutes to incorporate air (this makes it fluffy).
7. Add salt. Heat oil and fry small scoops until golden brown.
8. Served with: Pap (akamu), bread, or garri.
9. Moi-Moi (Steamed Bean Pudding) – Yoruba/Igbo favourite
10. Ingredients (serves 6–8):
    1. 2 cups cowpea flour or peeled beans
    1. 1 cup vegetable oil or palm oil
    1. 2 onions
    1. 3–4 Scotch bonnet peppers
    1. Salt, seasoning cubes
    1. Optional: Crayfish, boiled eggs, corned beef, fish
11. Method:
12. Soak and peel beans, then blend with onions and peppers into a smooth paste.
13. Mix in oil, salt, seasoning, and additives.
14. Pour into greased containers, banana leaves, or foil wraps.
15. Steam for 45–60 minutes until firm.
16. Served with: Rice, pap, or as a snack.
17. Gbegiri Soup (Yoruba Bean Soup)
18. Ingredients:
    1. 1 cup cowpea (brown or white variety)
    1. Palm oil, onions, peppers, locust beans (iru), dried fish or meat
    1. Seasoning, salt
19. Method:
20. Soak and boil cowpea until very soft, then mash or blend into a smooth soup base.
21. Fry ingredients in palm oil (stir-fry technique), add the bean puree and water to desired thickness.
22. Simmer for 15–20 minutes.
23. Served with: Amala, eba, or rice.
24. Akidi (Igbo Style Boiled Cowpea)
25. Simple everyday dish: Soaked cowpea boiled with salt, onions, and pepper. Often combined with yam, plantain, or rice.
26. Cowpea Leaves (Ewa Ijebu or Alefu)
27. Young leaves cooked as vegetable soup with melon seeds (egusi) or in stews for extra nutrition.

 Side Effects / Caution

1. General Safety Profile (Favourable)

Cowpea has been consumed as a staple food across Africa and Asia for centuries with no widely reported severe adverse effects. It is generally recognized as safe for normal dietary consumption.

• Oligosaccharides and Flatulence (Gas and Bloating)

Cowpea, like other legumes, contains oligosaccharides (raffinose, stachyose, verbascose)—complex sugars that are not digestible by human enzymes. These compounds pass into the large intestine, where they are fermented by gut bacteria, producing gas. This can cause:

• Flatulence (intestinal gas)
• Abdominal bloating
• Mild discomfort

Recommendation: Gradually increasing intake, thorough cooking, soaking dried beans before cooking (changing the water several times), and using traditional Nigerian methods like adding potash (kawun) or sodium bicarbonate during cooking can help reduce flatulence.

• Antinutrient Content

Like all legumes, cowpea contains some antinutritional factors including:

• Phytic acid: Can bind to minerals (iron, zinc, calcium) and reduce their absorption.
• Tannins: Can inhibit protein digestion and mineral absorption.

Reduction Methods: Traditional processing methods such as soaking, boiling, fermentation (e.g., in moin-moin preparation), and sprouting significantly reduce antinutrient levels. Cooking denatures most anti-nutritional factors.

• Allergic Reactions

Legume allergies, including allergies to cowpea, are rare but possible . Individuals with known allergies to other legumes (peanuts, soybeans, lentils, chickpeas) should exercise caution when trying cowpea for the first time.

Symptoms may include: Hives, itching, swelling of lips/tongue, difficulty breathing, or anaphylaxis (in severe cases).

• Medical Considerations (Specific Populations)
• Kidney Disease: Cowpea is rich in potassium. Individuals with compromised kidney function should monitor their intake and consult a healthcare provider .
• Diabetes: While cowpea is beneficial for blood sugar regulation, individuals on diabetes medications should monitor their blood glucose levels when incorporating cowpea therapeutically to avoid hypoglycemia .
• IBS (Irritable Bowel Syndrome): Individuals with sensitive digestive systems may need guidance on portioning and preparation .
• Drug Interactions

Given the plant’s documented antidiabetic, hypocholesterolemic, and antihypertensive properties:

• Antidiabetic medications: May have additive blood sugar-lowering effects.
• Antihypertensive medications: The potassium content and ACE-inhibitory potential may have additive blood pressure-lowering effects.
• Anticoagulant (blood-thinning) medications: The anti-sickling and thrombolytic properties suggest potential effects on blood coagulation; theoretical interaction exists.
• Proper Preparation is Essential

As with all legumes, cowpeas should never be consumed raw. Raw beans contain lectins (such as phytohaemagglutinin) that can cause food poisoning. Thorough cooking (boiling) denatures these harmful compounds and makes the beans safe and digestible.

• Moderation

As with any food, moderation is recommended. While cowpea is highly nutritious, excessive consumption may lead to digestive discomfort due to its high fiber and oligosaccharide content.

• Storage Concerns

Improper storage may lead to infestation by storage pests and contamination by molds.

References

• Abebe, B. K., and Alemayehu, M. T. “A Review of the Nutritional Use of Cowpea (Vigna unguiculata L. Walp) for Human and Animal Diets.” Journal of Agriculture and Food Research, vol. 10, 2022.
• Affrifah, N. S., et al. “Cowpeas: Nutritional Profile, Processing Methods and Products — A Review.” Legume Science, vol. 4, no. 3, 2022.
• Ayenan, M. A. T., et al. “Nutritional and Health Benefits of Cowpea (Vigna unguiculata): A Review.” Food Science and Nutrition, vol. 8, no. 8, 2020, pp. 4374–4385.
• Boukar, Ousmane, et al. “Cowpea (Vigna unguiculata L. Walp.): An Overview on Its Nutritional Facts and Health Benefits.” Journal of Food Composition and Analysis, vol. 82, 2019, article 103215.
• Boukar, Ousmane, et al. “Cowpea (Vigna unguiculata): Genetics, Genomics and Breeding.” Plant Breeding Reviews, vol. 36, 2013, pp. 215–270.
• Hall, Anthony E. “Cowpeas: Resilience to Drought and Heat in a Changing Climate.” Crop Science, vol. 52, no. 5, 2012, pp. 1973-1991.
• International Institute of Tropical Agriculture. Cowpea Production and Utilization in West Africa. IITA Publications, Ibadan, Nigeria.
• Jayathilake, C., et al. “Cowpea: An Overview of Its Nutritional Facts, Bioactive Compounds, and Health-Promoting Properties.” Food Production, Processing and Nutrition, vol. 3, no. 1, 2021, pp. 1-14.
• Kew Science. “Vigna unguiculata (L.) Walp.” Plants of the World Online, Royal Botanic Gardens Kew, powo.science.kew.org/taxon/urn:lsid:ipni.org:names:525534-1. Accessed 26 May 2026.
• Langyintuo, Augustine S., et al. “Cowpea Supply and Demand in West and Central Africa.” Field Crops Research, vol. 82, no. 2–3, 2003, pp. 215–231.
• Madodé, Yann E., et al. “Traditional Processing and Quality Attributes of Cowpea-Based Foods in West Africa.” International Journal of Food Science & Technology, vol. 46, no. 5, 2011, pp. 972-982.
• Moyo, A. A., et al. “Recent Trend on Phytochemistry, Nutraceutical and Therapeutic Potential of Underutilized Vegetable Cowpea (Vigna unguiculata L. (Walp)) in Healthcare Domains.” ScienceDirect, Oct. 2024, www.sciencedirect.com/science/article/abs/pii/S2950199724000971.
• National Research Council. Lost Crops of Africa: Volume II: Vegetables. National Academies Press, 2006.
• NIH National Library of Medicine. “Unveiling the Therapeutic and Nutritious Potential of Vigna unguiculata in Line with Its Phytochemistry.” Heliyon, vol. 10, no. 18, Sept. 2024, p. e37911. PubMed Central, doi:10.1016/j.heliyon.2024.e37911.
• Nwagboso, C., et al. “The Economic Importance of Cowpea in Nigeria.” CGSpace, 2024.
• Sardar, H., et al. “Unveiling the Therapeutic and Nutritious Potential of Vigna unguiculata (L.) Walp.” PMC, 2024.
• Singh, B. B., et al. Advances in Cowpea Research. Co-publication of the International Institute of Tropical Agriculture and Japan International Research Center for Agricultural Sciences, 1997.
• Timko, Michael P., and B. B. Singh. “Cowpea, a Multifunctional Legume.” In Genomics of Tropical Crop Plants, Springer, 2008, pp. 227–258.
• Wikipedia contributors. “Cowpea.” Wikipedia, The Free Encyclopedia, en.wikipedia.org/wiki/Cowpea. Accessed 25 May 2026.