This study demonstrates that this particular viscous fiber preparation, PGX®, is effective in lowering postprandial glycemia when either sprinkled or incorporated into commonly eaten foods and confirms earlier predictions that the GI of a food would be reduced.
Enrichment of the diet using soluble fiber is particularly attractive as it both increases the dietary fiber levels of the diet as is recommended by health agencies such as the American and Canadian Diabetes Associations and the American Dietetic Association [15–17] and it has the further benefit of lowering the GI of the diet with its accompanying potential for health benefits . A recent meta-analysis published in the American Journal of Clinical Nutrition by Barclay et al  found significant positive relationships between highest and lowest quartiles of GI and glycemic load and incidence of type 2 diabetes, coronary heart disease, gallbladder disease, and breast cancer. The protection associated with low GI or low GL diets were comparable to that seen with whole grain or high fiber intake . The results of this analysis again support the premise that reducing postprandial blood glucose excursions may be an important strategy to reduce development of certain chronic diseases. The NVP reduced the glycemic index of the cornflakes, rice, turkey dinner, and strawberry yogurt by 26%, 45%, 24% and 12% respectively. Using the classification for Brand-Miller et al (20), where low GI foods are defined as having a GI less than 55, medium greater than 55 and less than 70 and high GI foods as greater than 70, many of the foods could be reclassified with respect to their GI. Cornflakes was changed from a high GI food to a medium GI food, the rice from a high GI food to low GI food, the turkey dinner and the granolas from a medium GI food to a low GI food. The yogurt was already a low GI food, but addition of NVP induced a further, although modest, 12% reduction in GI. The ability of viscous fiber to lower postprandial glycemia has long been known [6, 21] however its effect has always been dependent on being intimately mixed with the carbohydrate in the food [22, 23]. Sprinkling of the fiber usually results in clumping and a loss of effect  and therefore necessitates more intensive food preparation if the effect is to be preserved. The results of this study confirms that incorporation of the fiber into the meal is still more effective than sprinkling as was illustrated by larger percent reductions seen with the granolas. Nevertheless, unlike unprocessed viscous fibers, significant reductions in postprandial glycemia were observed when the NVP was sprinkled onto the food. This property will allow greater flexibility of its use for the consumer.
To allow a direct comparison of the effectiveness of different substances in affecting the GI of a food, we proposed the term "GRIP" (Glycemic Reduction Index Potential) concept (CMJ). Previous studies estimated the GRIP of NVP to be 5 when added to liquids and 7 when added to a solid food [13, 25]. This study again confirmed that, on average the NVP reduced the GRIP by 7 units per gram of fiber and compares favorably with a fiber such as oat bran which has an estimated GRIP of 4 units per gram of fiber . As a consequence of the high GRIP factor of NVP, smaller quantities can be used to give equivalent results to other viscous fibers, doses of which ranged from 8-15 g [6, 27, 28], compared to the 5 g used in this study.
Limitations of this study include the relatively small number of meals and subjects tested and the acute nature of this study. Further studies need to be undertaken to confirm consistent effects across a wider range of foods, and whether the acute reductions seen translate in flattening of the fluctuations seen in glycemia during the day.