Several published human clinical studies have investigated the physiological effects of starchy foods in which SDS has been measured, and comparisons made on an equivalent available carbohydrate basis. Lower and more stable rates of glucose appearance into the body and lower post-meal blood glucose and insulin responses have been consistently observed when foods with high SDS content have been compared to foods with low SDS content.
The influence of the characteristics of cereal foods on postprandial glycaemic response has been evaluated using a database including 190 cereal products tested by the usual Glycaemic Index (GI) methodology. Slowly digestible starch (SDS), rapidly digestible starch (RDS) and fat and fibers, and several interactions involving them, significantly explain GI by 53% and Δpeak of glycaemia by 60%. Fat and fibers had important contributions to glycaemic response at low and medium SDS contents in cereal products, but this effect disappears at high SDS levels. In addition to the comparative studies discussed above, several other studies have identified an inverse relationship between a high content of SDS and decreased blood glucose and insulin responses in human subjects.
Healthy normal weight women (n=16) consumed a breakfast containing one of three high-SDS biscuit varieties or a low-SDS extruded cereal in a randomized crossover design. A decreased rate of glucose appearance and decreases in blood glucose and insulin responses were observed following consumption of the high-SDS breakfasts.
Healthy normal weight subjects (n=12) ate a breakfast containing either a food with SDS or a food low in SDS. The breakfast containing the SDS food led to a significantly lower and more stable rate of exogenous glucose appearance in the blood compared to extruded cereals low in SDS. No significant differences were observed under the conditions of the study with respect to the iAUC for blood glucose or insulin concentrations (T0-T120 min) despite a lower C-peptide secretion (at 90, 120, 150 min; p≤0.05). It was suspected that measuring plasma glucose and insulin only every 30 minutes led to an imprecise description of blood glucose and insulin evolution. In order to confirm this hypothesis, a second clinical trial was conducted in similar conditions (similar population (n=13) and same breakfasts) to duplicate the results on glycaemia and insulinaemia, with more precision due to a more frequent blood sample collection. For the first 2 hours, plasma glucose and insulin were significantly lower after the breakfast with the SDS containing food.
Healthy overweight men and women followed either a high-GI diet including a breakfast with a low-SDS extruded cereal (n=19) or a low-GI diet including a breakfast with a high-SDS biscuit (n=19) during a 5 week dietary intervention. A lower and more stable rate of glucose appearance was observed following the high-SDS breakfasts and the blood glucose response was moderate.
The correlation between SDS and GI measured in vivo was investigated in 24 plain biscuits. A significant inverse correlation between GI and SDS was found (r=-0.41; P=0.04).
Obese and insulin-resistant (but non-diabetic) individuals (n=9) consumed a high-energy test meal including low-SDS wheat flakes or biscuits with SDS in a randomized crossover design. Decreased blood glucose and insulin responses (iAUC, 0-120 min) were observed.
The impact of different carbohydrate fractions and macronutrient content of cereal products on GI measured in vivo was investigated in 23 cereal products (3 groups: biscuits, bakery products, breakfast cereals). It has been shown that the main parameter explaining GI was SDS (r=-0.79; P<0.01). The biscuit group, which had the highest SDS content due to a low level of starch gelatinization, was found to have the lowest GI values compared to the bakery products and breakfast cereals groups.