Dietary changes are always recommended but never really studied, especially in Mauritius where the concept of GI is still new and exposure to low-GI foods in traditional diets is very limited. As the GI of a food represents the degree that a particular food can raise the blood glucose after consuming it, it is important to study its effect in people and thus confirm the laboratory attributed GI which is based on structure. This study is a short-term randomized controlled study to assess the effect of incorporating a novel low-GI sugar into portion-controlled diet on the glycemic control in type 2 diabetes patients in Mauritius. As a by product of the study design, it confirms the rise in consciousness following implantation of the CGM and change in eating behavior, leading to more controlled sugar levels. This, in terms of average blood sugar over a medium term assessment (first 4 days of study) and in terms of levels of variation, examined over the first phase of the study itself. Surprisingly, participants apprehended the upcoming controlled portion period, and relaxed on their self-motivational gains. Between the last day of the normal diet and first day of controlled diet, blood sugar levels increased, and higher variations were noted across subjects.
While most studies from the existing literature focused on the impact of low-GI diets, this study examined the effect of low-GI sugar per se, as part of an overall low-GI dietary. The low-GI-sugar group showed a more pronounced reduction in average sugar levels when compared to the normal-GI-sugar group. This reflects the lower HbA1c noted during consumption of low-GI diet, a frequently analyzed end-point [1]. It is worth noting that a reduction as little as 1% in mean HbA1c reduces the risks of diabetes-related complications significantly [16]. The results are more interesting just after embarking on the second phase of the study, that is, just after starting to consume controlled portions. This is suggestive of enhanced compliance at earlier timepoints of the study, a phenomenon that is not uncommon or unknown in clinical trials [17, 18].
Fasting blood sugar (CGM from 5:00 to 6:00 in the morning) exhibited the same patterns as noted overall; improved glycemic control was detected as early as just after implantation of CGM, despite participants instructed to eat ad libitum during the first phase. Along the controlled portion period, improvements were maintained in terms of average blood sugar, without any obvious distinction between the two treatment groups. However, variations occurring at that time of the day showed promising results for the low-GI group, with a consistent reduction from D5 to D10.
Postprandial glycemic control was enhanced during the second phase, i.e. when subjects were consuming low-GI diets. Lower variations were noted between noon to 13:00, typical post lunch-time period, irrespective of the group they were assigned to. Lower variations were observed on D7 for the low-GI group. Post-lunch glucose levels have been observed to account for a relatively larger portion of HbA1c [19]. Our observation of lower postprandial, more specifically, post-lunch excursions, is clinically significant and is likely to lead to improved glycemic control defined as a reduction in HbA1c and ultimately lower incidence of diabetes-related complications.
Over the 10-day observation period, a steady decreasing trend was recorded when the CGM data was averaged between 23:00 to midnight. Moreover, lower peaks were noted for the low-GI sugar group during the second phase, and the level of variation was consistently lower across evaluation days, indicating enhanced glycemic control during sleep compared to normal-GI sugar. The results support the rather widely accepted notion that low-GI foods lead to a sustained rise in blood glucose levels, i.e., a sustained decrease in postpandrial glucose level with less glycemic peaks [20]. A decrease in the latter is shown to be associated with improvements in insulin sensitivity [20], decreased insulin resistance and loss of weight (spike in insulin bring about weight gain) [21].
The findings of this study, that involved the use of a novel sugar with a remarkable difference in GI of 49 units, are contrary to those from similar previous studies among non-diabetic and obese/overweight patients, whereby even moderate to large differences in GI did not affect 24-hr glucose concentrations [22, 23]. But on another occasion, a GI difference of as little as 8 units resulted in improved 24-hour glucose concentration [24]. Glycemic variability, which is a clinically important characteristic of low-GI foods, was not assessed in any of the above studies. Moreover, all these studies had been performed in non-diabetics.
One limitation of this study is that the majority of the participants included were retired individuals who spend most of their days being sedentary, the effect was thus not studied on individuals who are more physically active. Moreover, with more time on their hands, the participants were able to consume the 5-meals per day provided to them. Five meals were provided in an attempt to reduce the number of drop-outs due to perceived insufficient amount of food. We could expect the study to produce better results with a 3-meal plan; a decrease in the total number of GI consumed over a period of 24-hours. The effect on weight was not investigated (too short period to notice a change in weight). Food intolerances were not investigated, more specifically the effect of gluten in the meals was not investigated.
Unlike the DASH (Dietary Approach to Stop Hypertension) diet [25] for hypertension, there is no universal approach to a diabetic diet and there exists, till date, some controversies about the usefulness of low-GI diets.