Dika Nut

Irvingia gabonensis is a large evergreen tree of lowland tropical forest, growing up to thirty-five metres. It produces a yellow-green fruit that looks like a small mango, with a fibrous, sweet to sour pulp surrounding a large, flat, hard-shelled stone.

Inside the stone is the kernel, called dika nut or ogbono in some regions. It is pale cream to light brown, flat and oval, about two to three centimetres long, with a fatty, slightly bitter, mild and nutty flavour. The kernels are sold whole, dried, ground into a coarse meal, or pressed into a paste or hard cake known as dika bread. Their most notable feature is the sticky, slippery texture they give when cooked in liquid.

The tree is native to the humid forest zone of West and Central Africa, from Nigeria and Cameroon through Gabon, Congo and Angola. It grows wild and is also kept in farms and home gardens, and it is one of the most important of the tree species whose products are harvested from the forest.

The genus name honours Edward Irving, a nineteenth-century Scottish surgeon and botanist who worked in West Africa, and gabonensis means from Gabon. Dika is a name used by several local languages in the region, and ogbono is the Igbo name for the kernels in Nigeria. The English names wild mango and bush mango reflect the superficial resemblance of the fruit to the true mango, though the plants are not closely related.

Dika nut has long been an essential food and trade item in the forests of West and Central Africa. People collect the fruits during the rainy season, eat or sell the pulp, and then crack the stones to obtain the kernels, which are dried and stored for many months. The kernels have been traded in local and regional markets for generations and also move to African communities overseas.

In cooking, ogbono soup in Nigeria and similar thickened soups in Cameroon and Gabon rely on the kernel's gelling quality. In Gabon and Cameroon the kernels are pounded into dika bread, which keeps well and is used as a thickener and seasoning in sauces. The tree is also valued for its timber, shade and role in agroforestry systems.

In the late twentieth and early twenty-first centuries the species attracted attention from agricultural research organisations such as the World Agroforestry Centre, which began domestication programmes to select superior trees and spread cultivation, and from the supplements industry, which marketed seed extracts for weight management. Research interest has focused on its oil and fibre. At the same time, over-harvesting and forest clearing have raised concerns for wild populations in some areas.

The ground kernels are the base of thick, slippery soups, often cooked with leafy greens, fish, meat and palm oil. The kernels may also be pressed into dika bread or paste for storage and used as seasoning in stews. The kernel fat, which is solid at room temperature, can be extracted for cooking, soap and cosmetics, and it is also known as dika butter.

The pulp of the fruit is eaten fresh or turned into juice, jam and wine. Bark, leaves and seeds feature in traditional remedies, and the timber is used for local construction. The trees are kept in farmland for shade and income.

Dika kernels are very high in fat, mostly medium-chain saturated fatty acids such as lauric and myristic acid, and contain some protein and soluble fibre, which explains their thickening power. Small clinical trials of seed extracts for weight and cholesterol have been published, but they are short, often involve commercial supplements and vary in quality, so firm conclusions cannot be drawn.

As a traditional food eaten in modest portions in soups, it is part of a normal diet in the regions where it grows. Because of its fat content, it is energy-dense.