Abuja — A tea made from the leaves of an indigenous African tree and bitter oranges is showing promise as a treatment for type 2 diabetes.

The tea, prepared by boiling leaves from the Rauvolfia vomitoria tree - known as 'asofeyeje' in the West African Yoruba language - with fruit from the bitter orange tree, appears to regulate blood sugar levels, according to principal investigator Joan Iyabo Campbell-Tofte, a postdoctoral researcher at the University of Copenhagen, Denmark.

Type 2 - or adult-onset - diabetes is a life-threatening condition characterised by high levels of sugar in the blood. Often associated with obesity, the disease occurs when the body doesn't make enough - or doesn't properly use - the hormone insulin. Insulin moves sugar into cells, where it is needed for energy.

For the Danish study, 23 patients with type 2 diabetes drank 750 millilitres of asofeyeje tea every day while a control group drank a placebo. After four months, there was a reduction in blood sugar levels among asofeyeje tea drinkers. The results of the study have yet to be published.

Campbell-Tofte, who studied and later lectured at the University of Nigeria, says the tea seems to work differently from conventional diabetes treatments. Existing drugs aim to rapidly clear excess sugar from the bloodstream, while the tea appears to reduce blood sugar over time.

The researchers speculate that the tea works by improving the ability of polyunsaturated fatty acids in muscle fibres to transport sugar into cells.

Campbell-Tofte told SciDev.Net that she learnt about the tea from family and friends, who harvested 50 kilograms of leaves from the asofeyeje tree and 300 kilograms of bitter oranges for the research in the Nigerian state of Edo, where she grew up.

But though Campbell-Tofte is optimistic about the tea's therapeutic potential, she warns that any new treatment for diabetes would come "years from now".

The asofeyeje tree is native to Cameroon, Democratic Republic of Congo, Ghana, Liberia, Senegal, Sudan and Uganda. Traditional healers also use it as a purgative and a treatment for psychiatric conditions, leprosy and arthritis.