Glycaemic responses of some legumes in Nigeria using non-diabetic subjects

Abstract

Background: It is established that legumes generally have a low glycaemic index (GI) which means that they raise blood glucose levels very little. However, the glycaemic responses to normal subjects and the GI of these local legumes are not yet established.

Objective: This work determined the postprandial glycaemic responses of  non-diabetic Nigerian subjects to four different legumes.

Methods:The legumes studied were cowpeas, (Vigna unguiculata), African yam bean (Sphenostylis stenocarmpa), Pigeon pea (Cajanus cajan), and Bambara groundnuts (Voandzeia subterranean Thouars). The proximate compositions of the dried, mature legume grains were determined. They were cleaned and washed in clean water, cooked for about 10 minutes, re-washed while the cooking water was drained off. They were cooked for another 20 minutes adding only salt (for taste), and finally transferred to a pressure pot to cook for another 40 minutes until they were done (softened). The amounts that would deliver 50g carbohydrates were served to the subjects after an overnight fast. Thirty nondiabetic subjects were used for the study. Glucose solution (50g in 300ml potable water 25°C 1:6 w/v) was also fed to the subjects. Glycaemic responses were calculated after 0, 30, 60, 90 and 120 min. Glucose response curves were, therefore, constructed.

Result: The results indicated that the Glycamic Index (GI) was lowest for African Yam Bean (34±4). Cowpea and Pigeon pea had the highest GI value (36±3 and 36 ±4), respectively. Bambara nut had 35±5.

Conclusion: The local legumes elicited low postprandial rise in blood glucose in non-diabetic subjects. African yam bean should be the most preferred choice of the legumes for diabetic patients.

Key words: Local legumes, glycaemic index, postprandial glucose.