Abstract

Objective
Physical modifications of foods have been known to play a significant role in dietary
management of diabetes. This study is aimed at assessing the effect of physical modification of
yam on plasma glucose response in both diabetic and non-diabetic Nigerians.
Materials and Methods
A total of forty-eight subjects were studied, comprising twenty-four diabetics and
twenty-four non-diabetics with a sex ratio of 1:1. White yam specie (Dioscorea rotunda) was
used and modified into three forms of boiled yam, pounded yam and browned yam flour
(amala). Weighed amount of the yam meals containing 50g carbohydrate (glucose) equivalent
were eaten by the subjects. The values of the mean Plasma Glycaemic Response Indices
(PGRI); PPG, MIPG, IAUGC and 2HPPG were determined for the foods in all the subjects.
Fifty grams of glucose was also given to the non-diabetic subjects only in other to determine
the glycaemic indices (GI) of the food preparations.
Results
The mean age (40.04±1.16 vs 37.83±1.42years), BMI (23.92±0.46 vs
23.64±0.46kg/m2), height (1.62±0.01 vs 1.63±0.01m) and weight (63±1.19 vs 62.72±1.54kg)
were comparable in both diabetics and non-diabetics, respectively, while the mean recruitment
FPG (5.5±0.14 vs 4.57±0.16mmol/l; p<0.05) was significantly higher in the diabetic group.
The mean PPG was significantly higher in the diabetics compared with the non
diabetics (p<0.05) for all the yam meal studied. However the mean PPG were still below the
recommended level for diabetic control. The mean MIPG was significantly higher in the
diabetics compared with the non-diabetics (p<0.05) for the boiled yam (4.3±0.4 vs 1.9±0.3)
and amala (1.8±0.2 vs 1.3±0.2). The mean IAUGC was higher in the diabetics groups
compared with the non-diabetics but only achieved statistical significance with boiled yam
(276.1±21 vs 128.3±19.3; p<0.05). The mean 2HPPG were significantly higher in the diabetics
groups compared with the non-diabetics (p<0.05) for all the yam meals. However the mean
2HPPG level was below the recommended level for diabetic control.
There was no statistical difference (p>0.05) between IAUGC after the glucose load when the
three groups of non-diabetics that took the yam meals were compared. The glycaemic indices
(GI) of the yam meal are 36.8%, 52.9% and 81.6% for amala, boiled yam and pounded yam
respectively.
Conclusion
Amala that undergo the highest degree of process before been consumed showed the
least GI. This is contrary to previous views that the more processed/refined a food is the higher
the glycaemic response. The process of gelatinization and subsequent retrogradation of the
starch in the preparation of the yam flour could have accounted for this difference.

GLYCAEMIC RESPONSE TO THREE DIFFERENT PREPARATIONS OF WHITE YAM IN DIABETIC AND NON-DIABETIC NIGERIANS