Glycemic index of bread : fiber or minerals? this is the question -

Abstract

Glycemic index (GI) of food is known to be positively associated with the development of several diseases including type II diabetes. Modest dietary changes from high to low GI foods have shown beneficial effects. These findings have been translated to recommendations for increased dietary intake of whole grains. Trials of added cereal fiber however, have failed to induce a protective effect and fiber has thus been proposed to be a marker of other components of whole grains that impart health advantages. Whole wheat grains are known to be a rich source of several minerals (phosphorus, potassium and magnesium) that play a role in glucose metabolism, and are depleted during the process of refinement. Thus, it is plausible to hypothesize that the benefits of whole grains previously ascribed to their fiber content are in fact due to these minerals. Therefore, the proposed research aims to restore and fortify white bread with these minerals and determine their resulting GI. This is a single blind cross over design study. Twelve healthy male subjects were recruited, and asked to complete a total of four visits. On each visit, participants consumed in random order one of the 4 different types of bread: white bread (WB), whole grain bread (WG), restored bread (WB-R), and fortified bread (WB-F). Blood samples were collected at fasting, 15, 30, 45, 60, 90 and 120 minutes post meal ingestion. Serum glucose, insulin, GLP-1, GIP, triglycerides, phosphorus, magnesium, and potassium were measured. GI was measured according to the trapezoidal rule of geometry and area under the curve. WB-R and WB-F significantly retained the lowest levels of glucose at 60 minutes onwards, while insulin levels remained unaltered and did not show any significance. Both WB-R and WB-F also maintained significantly lower triglyceride levels than the WB group. Serum phosphate levels were significantly higher in WB-R and WB-F. Similarly, serum potassium levels were significantly higher in WB-F at 120 minutes. Serum magnesium, GLP-1, and GIP did not s