In their otherwise fine article concerning recommendations for the management of diabetes during Ramadan, Al-Arouj et al. (1) perpetuate an ingrained, but mistaken, view of the glycemic response to different kinds of ingested carbohydrates. Their recommendations of eating foods containing complex carbohydrates at the predawn meal and simple carbohydrates at the sunset meal is based on their stated assumption that digestion and absorption of the former is delayed and faster for the latter. These assumptions have been challenged by clinical research. For instance, Wahlquist et al. (2) showed in normal subjects and one type 2 diabetic patient that glucose appearance in the circulation was independent of saccharide chain length. Hydrolysis is so rapid in the gastrointestinal tract that the rate of glucose absorption from ingested monosaccharides (glucose) and polysaccharides (starch) was equivalent.
Therefore, one might expect that the amount of simple carbohydrate in the diet might not have much impact on postprandial glucose excursions. This was studied by measuring the effect of different proportions of simple and complex carbohydrate in meals in which total carbohydrate remained constant at 50% in type 2 diabetic patients (3). Three different ratios of complex to simple carbohydrates were evaluated: 80:20, 50:50, and 20:80. Glucose and insulin concentrations were measured hourly all day long, as was urinary glucose collected throughout the day. The results were similar in all three diets with small, but statistically significant, increases in plasma and urinary glucose levels in the diet containing 80% complex carbohydrate compared with the other two. It should be emphasized that all of the simple carbohydrate was from naturally occurring sugar in fruits, vegetables, and dairy products. No refined sugars were added to any of the diets. These results may be due, in part, to the fact that the natural sources of simple carbohydrate contained more fiber than foods furnishing the complex carbohydrate. However, it is now accepted that meals containing sucrose, incorporated into foods or desserts or even sprinkled onto cereal, do not lead to higher postprandial glucose excursions in either type 1 or type 2 diabetic patients (4,5,6). The latter observations are obviously independent of fiber. Thus, the type of carbohydrate, i.e. simple or complex, does not influence postprandial glycemic excursions.
