Long-term influence of a wheat-bran supplemented diet on secretion of gastrointestinal hormones and on nutrient absorption in healthy man.

: Responses of gastric inhibitory polypeptide (GIP), gastrin and vasoactive intestinal polypeptide (VIP) to a test meal and also nutrient absorption were measured in five healthy men before and after 1, 3 and 7 weeks of daily ingestion of 20 g of wheat bran added to a normal balanced diet. Basal levels of the three hormones were not affected by bran ingestion. Bran ingestion induced a progressive decrease of GIP response to the test meal which became significant after 7 weeks at 30 min (373.9 +/- 71.4 vs 231.1 +/- 47.8 pg/ml, mean +/- s.e.m., P less than 0.05) and at 180 min (389.4 +/- 43.9 vs 262.2 +/- 37.9 pg/ml, P less than 0.01). Gastrin release did not change except for a slight but not significant decrease after 3 weeks. There was no VIP secretion after meal ingestion and addition of bran caused no change. Blood glucose response decreased with time with the greatest effects during the third week with fibre at 30 min (5.00 +/- 0.50 vs 7.38 +/- 0.05 mmol/l before bran), and at 60 min (3.88 +/- 0.34 vs 5.94 +/- 0.27 mmol/l before bran, P less than 0.05). Wet and dry weight of faeces increased by at least 60 per cent from the first week with bran onwards. Faecal nitrogen and fat also increased from 1.77 +/- 0.16 to 2.44 +/- 0.13 g/d for nitrogen (P less than 0.02) and threefold for fat (from 3.78 +/- 0.58 to 10.35 +/- 0.67 per cent dry weight, P less than 0.005) at the third week. Fat and nitrogen contents remained higher until the end of the experiment.(ABSTRACT TRUNCATED AT 250 WORDS)