Nutritional Composition and Glycaemic Index of Three Varieties of Yam Consumed in Ekiti State

Yam is a dietary staple across Ekiti State and much of southwestern Nigeria, providing a major proportion of daily carbohydrate and energy intake, yet comparative data on the nutritional composition and glycaemic index of the locally dominant varieties are limited. This study determines the proximate composition and glycaemic index of three yam varieties commonly consumed in Ekiti State: white yam (Dioscorea rotundata), water yam (Dioscorea alata), and yellow yam (Dioscorea cayenensis). Yam samples were obtained from Ado-Ekiti central market, boiled by standardized procedures, and subjected to proximate analysis by AOAC methods. Glycaemic index was determined using the FAO and WHO standardized protocol in human subjects, recruiting thirty apparently healthy adult volunteers who consumed a portion of each yam variety delivering 50 grams of available carbohydrate after an overnight fast. Blood glucose was measured at 0, 15, 30, 45, 60, 90, and 120 minutes post-consumption using glucometers, and incremental area under the curve was calculated relative to a glucose reference standard. Results show that white yam had the highest carbohydrate and energy content, while water yam had the highest moisture content and lowest energy density. Glycaemic index values were 71.4 for white yam, 62.7 for water yam, and 66.3 for yellow yam, classifying all three as medium-to-high glycaemic index foods. These data have implications for dietary management of diabetes and metabolic syndrome in the region. Keywords: yam varieties, glycaemic index, proximate composition, Ekiti State, Dioscorea.