A comparative study of the glycaemic index of orange-fleshed sweet potato (Ipomoea batatas) with the indigenous sweet potato commonly consumed in Abeokuta metropolis, Ogun State, Nigeria

Abstract

Background: Advocacy of orange-fleshed sweet potato (OFSP) consumption as an essential crop in many developing countries to alleviate vitamin A deficiency due to its beta carotene bio-fortification. It is crucial to assess its glycaemic index (GI) compared to the indigenous sweet potato (ISP) for therapeutic meal planning. 
 Objective: This study aimed to determine and compare the GI of orange-fleshed sweet potato and indigenous sweet potato commonly consumed in Ogun State, Nigeria.
 Materials and Method: OFSP and ISP were obtained from a farmers' market at Abeokuta, Nigeria. Ten healthy individuals within the age range of 18 and 24 years were recruited. Volunteers were served with equivalent test foods (250g of OFSP and 200g of ISP) to give 50g of available carbohydrates. The boiled potatoes were served plain after 11-12 hours overnight fast and tested the subject's blood glucose at different times. The incremental area under the curve (IAUC) was determined using Microsoft Excel, and the GI was calculated. Statistical Package for Social Sciences was used to calculate the mean, standard deviation, and correlation. Statistical tests were significant at p ≤ 0.05.
 Results: ISP had greater carbohydrate content (24.33g±0.20) than OFSP (18.87g±0.26). The mean GI of OFSP was 81.36g±7.17, while that of ISP was 85.50g±7.26. There was no significant difference (p>0.05) between the GI of OFSP and ISP at 30, 60, and 120 minutes, whereas found a significant difference (CI-95%) between the GI of OFSP, ISP, and glucose at 90 minutes.
 Conclusion: The OFSP and ISP consumed in Ogun state have a high GI, although OFSP had lower GI compared to ISP. However, the GI values for these test foods were not significantly different.