Rye bread does not produce as high a spike in insulin after meals as wheat bread, and the difference is not explained by the fiber content in rye bread, researchers report.
After a meal, the pancreas releases insulin into the blood to process the post-meal rise in blood sugar. Some experts believe that the repeated high post-meal spikes in insulin that occur in a high-carbohydrate, high-snacking diet may increase the risk of insulin resistance and eventually type 2 diabetes.
Previous research has shown that rye bread triggers a smaller increase in insulin after a meal than does wheat bread. The reason for the difference is uncertain. It could be a result of differences in the fiber content of wheat and rye bread or of structural differences between the two types of bread.
Fiber does not seem to account for the difference, according to a team at the University of Kuopio in Finland. The researchers compared increases in blood sugar and insulin in 19 women after they ate several different types of bread - wheat bread and three types of rye bread that contained different amounts of rye fiber.
Compared to wheat bread, all three types of rye bread produced a lower insulin response, according to the report. The lower response was not due to fiber content, since fiber content was not the same in all varieties of rye bread.
Lab experiments showed that rye starch broke down more slowly than wheat starch, and the research team concludes that structural differences between wheat and rye bread may account for their different effects on insulin levels.
All types of bread produced similar post-meal surges in blood sugar. However, blood sugar dropped slightly below normal after the women ate wheat bread, presumably because of excess insulin production; this did not happen with the rye breads.
Below-normal levels of blood sugar could increase hunger and encourage snacking, according to the researchers.
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