Long-term evolution of the effect of bran ingestion on meal-induced glucose and insulin responses in healthy man

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Abstract
The long-term effect (7 wk) of the addition in the diet of 20 g of wheat bran was studied in five healthy subjects. Blood glucose and plasma insulin were assayed during testmeals taking place before (I), then 10 days (II), 24 days (III), and 45 days (IV) after daily ingestion of wheat bran. Bran addition leads to a time progressive reduction of meal-induced glucose response. This effect was the strongest during meal III, at 30 min (from 7.38 ± 0.11 to 5.0 ± 1.11 mmol/1; p < 0.05) and at 60 min (from 5.94 ± 0.61 to 3.88 ± 0.78 mmol/1; p < 0.05). Insulin response remained identical during the first three test meals. It increased then in a significant manner during meal IV, at 60 min (From 45.5 ± 12.3 to 61.8 ± 8.9 µU/ml; p < 0.02), and at 120 min (from 41.2 ± 16.3 to 61.0 ± 16.0 µU/ml; p < 0.05). The causes of the reduction of glucose response could be potential gastric emptying and intestinal transit increases. The exact mechanism of the improved long-term glucose tolerance seen in bran is not obvious nor is the reason for the enhanced insulin response seen later.