Key words: dietary management of diabetes, glycemic index, Nigerian staple foods

The upsurge in the incidence and prevalence of diabetes worldwide and in Nigeria in particular is a challenge for urgent action in the adoption of appropriate dietary management in patients with diabetes and also in the prevention of diabetes. Knowledge of the glycemic index (GI) of food types is essential for rational advice on calorie recommendation. Unfortunately, the GI of many food types in Nigeria is not known and so this study was undertaken to determine the GI of four staple and predominantly carbohydrate-based food types in Nigeria (yam, cassava, maize and wheat) by an open-labeled method, and to assess the variability of the GI of the tested food types in healthy subjects and those with diabetes. A total of twenty subjects were included in the study, i.e. ten type 2 diabetes mellitus (DM type 2) patients and ten healthy subjects serving as controls. They were given measured portions of the food containing 50 g of digestible carbohydrate. Blood glucose concentrations were determined from capillary blood drawn half hourly with a portable glucometer for two hours after ingestion of the food. Blood glucose curves were constructed to calculate the GI of the food. Values of the GI of the foods were compared using appropriate statistical methods of Microsoft Excel and SPSS v. 11. The results showed that there was wide variability of the GI in all the foods tested in both groups. In healthy subjects, maize flour meal had the lowest GI and cassava flour meal the highest GI. This was in contrast to patients with diabetes, where yam flour had the lowest GI and wheat flour the highest GI. While the method of meal preparation may have an effect on the overall acceptability of the food to our patients with diabetes, it is apparent that carbohydrate from yam should be allowed freely in the menu while that from wheat flour (white bread) should only be allowed sparingly. The results from this study should serve as an encouragement for further studies on the local staple food types in Nigeria to ascertain their suitability or otherwise in their incorporation into the recommended menu in the dietary management of diabetes.