Dolichos biflorus, widely known as horse gram or kulthi bean, is one of the oldest cultivated legumes in South Asia. In Sri Lanka it goes by the Sinhala name kollu, and across southern India it carries the same Tamil label. Despite its modest appearance — small, mottled seeds ranging from reddish-brown to near-black — horse gram punches well above its weight in nutritional value and cultural significance.
What makes horse gram nutritionally significant?
Horse gram is widely cited among researchers as one of the most protein-dense legumes available, with crude protein content that can exceed 20–25 percent of dry weight depending on the variety and growing conditions. It is also notably high in dietary fibre, iron, calcium, and polyphenols. Unlike many high-protein legumes, it is low in fat, making it a practical staple for communities that need affordable, shelf-stable nutrition.
The grain is comparatively rich in slowly digestible starch, which means it produces a lower glycaemic response than many other pulses. This property has attracted attention from nutritionists studying traditional diets in Sri Lanka and southern India, where horse gram has been eaten for centuries without the benefit of modern dietary science to explain why it worked.
How is horse gram used in Ayurvedic practice?
In classical Ayurvedic texts, horse gram — referred to as kulattha — is considered a heating food that supports digestion and kidney function. Traditional formulations use both the seeds and the water in which they have been soaked or boiled. This liquid, sometimes called kollu rasam in South India, is prescribed in folk medicine for conditions ranging from urinary complaints to respiratory congestion.
Ayurvedic practitioners in Sri Lanka incorporate the seed into preparations intended to manage weight and metabolic imbalance. The grain is often lightly roasted before use, which reduces certain anti-nutritional factors and improves palatability. Horse gram also appears alongside other plant-based ingredients in compound herbal preparations; Yogaraja Guggulu is one traditional Ayurvedic formulation that combines multiple botanicals in a similar therapeutic tradition.
Where is Dolichos biflorus grown and why is it suited to dry conditions?
Horse gram is cultivated across India, Sri Lanka, Malaysia, parts of Africa, and the West Indies. Within Sri Lanka it is predominantly a dry-zone crop, grown in the North Central and Northern provinces where rainfall is seasonal and soils can be thin and lateritic. The plant tolerates poor soils and short drought periods that would stress most other legumes, making it a valuable rotation crop in rain-fed farming systems.
Because it fixes atmospheric nitrogen through root nodules, horse gram improves soil fertility when incorporated into crop rotations — an important characteristic in subsistence agriculture. Farmers in the ancient irrigated civilisations of the dry zone, whose agricultural traditions are visible in places like Polonnaruwa, relied on a range of hardy legumes to maintain soil health between rice cycles.
Why is it called horse gram?
The common English name originates from the traditional practice of feeding the raw or boiled grain to working horses and cattle, particularly in South Asia. The high protein content supports muscle development and stamina in draught animals, and the grain stores well without refrigeration — both practical virtues for livestock managers in tropical climates. The name reached English-language texts through colonial-era botanical surveys of India and Sri Lanka, and it has remained in use ever since, even as the grain's role in human diets has grown in visibility.
How is horse gram eaten in Sri Lankan and South Indian cooking?
In Sri Lankan kitchens, kollu is prepared in several ways. The most straightforward is a simple curry — seeds soaked overnight, then cooked with coconut milk, turmeric, mustard seeds, and dried chillies. A drier preparation stir-fried with grated coconut and spices, called a mallum style dish, is also common. The grain can be sprouted and eaten raw in salads, or roasted and ground into a flour used in flatbreads.
In southern India, horse gram forms the base of kollu rasam (a thin, peppery broth) and kollu sundal (a spiced legume snack). The dried seed is dense and requires long soaking — typically eight to twelve hours — before cooking to soften the seed coat and reduce cooking time. Unlike red lentils, which dissolve when cooked, horse gram retains its shape, giving finished dishes a firm, slightly chewy texture.
What research has been done on Dolichos biflorus?
Scientific interest in horse gram has grown steadily over the past two decades. Studies published in food science and clinical nutrition journals have investigated its potential role in managing obesity, type 2 diabetes, and kidney stones. Researchers have isolated compounds including polyphenols and protease inhibitors that appear to slow carbohydrate digestion and reduce lipid absorption in animal models.
Work on anti-urolithiatic properties — the ability to inhibit kidney stone formation — has been particularly active, with several in-vitro studies suggesting that extracts of Dolichos biflorus seeds reduce the crystallisation of calcium oxalate. This aligns with longstanding Ayurvedic claims about the grain's benefit for urinary health. As with much ethnobotanical research, results from laboratory settings have yet to be fully validated in large clinical trials, so the findings should be understood as promising rather than conclusive.
How does horse gram compare to other legumes?
| Legume | Approximate protein (per 100g dry) | Key trait |
|---|---|---|
| Horse gram (Dolichos biflorus) | ~22–25 g | Drought-tolerant; low fat; high polyphenols |
| Red lentil (Lens culinaris) | ~24–26 g | Fast-cooking; widely available; mild flavour |
| Chickpea (Cicer arietinum) | ~19–21 g | Versatile; high fibre; good zinc content |
| Black-eyed pea (Vigna unguiculata) | ~23–24 g | Heat-tolerant; good iron source |
The figures above are indicative ranges drawn from nutritional databases; actual values vary with variety, growing conditions, and processing method.
Is horse gram available in Sri Lanka's markets?
Kollu is sold in dry-goods shops and weekend markets throughout Sri Lanka, typically in loose bulk form or in small sealed packets. It is far more prevalent in the north and north-central dry zone, where it is locally grown, than in the wet-zone coastal towns. Colombo's larger supermarkets often stock it alongside other dried pulses, and it is a regular feature in Ayurvedic dispensaries as both a raw ingredient and a component in pre-formulated products.
Visitors interested in Sri Lanka's botanical and culinary heritage will find horse gram part of a wider tradition of plant-based foods and medicines that stretches back thousands of years. The island's pharmacopoeia of medicinal plants — which includes well-known species such as Pongamia pinnata and the native acacia used in traditional woodworking, Acacia chundra — reflects the same empirical relationship between agriculture, ecology, and health that produced the horse gram traditions still alive today.
