A Comparative Study and Determination of Glycemic Indices of Three Yam Cultivars (Dioscorea rotundata, Dioscorea alata and Dioscorea domentorum)

The Glycemic Indices (GI) of three yam cultivars commonly consumed in Nigeria were studied. The yam cultivars were white yam (Dioscorea rotundata Poir), water yam (Dioscorea alata) and three-leaved yam (Dioscorea domentroum). Five normal (healthy) volunteers participated in the study. GI was determined using a standard method with glucose as the reference food. Fifty (50) gram available carbohydrate portions of the yam cultivars were analyzed for proximate composition and dietary fiber by enzymatic-gravimetric method. The mean IAUCs (glycemic responses) for the test foods and glucose ranged from 863.5-3642.84 and were significantly different. Expectedly, glucose had the highest glycemic response of 3642.84. The mean IAUC for white yam, water yam and three-leaved yam were 2386.50, 863.50 and 1929.08 respectively. The GI of white yam (67) and three-leaved yam (56) were significantly higher than that of water yam (24). It was concluded that white yam and three-leaved yam are intermediate or medium glycemic food, whereas water yam is a low GI food.