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Gastroenterol Clin Biol. 1995 Jan;19(1):20-6.

Nitrogen movements in the upper jejunum lumen in humans fed low amounts of casein or beta-lactoglobulin.

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  • 1Unité de Nutrition Humaine et de Physiologie Intestinale, Institut National de la Recherche Agronomique, Faculté des Sciences Pharmaceutiques et Biologiques, Paris.



To compare the progression of milk proteins in the upper part of the digestive tract, gastro-jejunal nitrogen movements were studied in 6 healthy human volunteers after beta-lactoglobulin and casein ingestion. 400 mL of water (control), purified beta-lactoglobulin (20 g/L) or casein (20 g/L), each adjusted to 25 microCi with 14C-polyethylene glycol, were given per os. Samples were collected in the stomach and 20 cm below the Treitz ligament every 20 min for 2 hours and measured for volume, osmolarity, ions and nitrogen content.


The jejunal flow rate peaked in the 0-20 min period following water and beta-lactoglobulin ingestion, and in the 20-40 min period after casein ingestion. The gastric half-emptying time (T1/2 min) of the liquid phase was significantly different (P < 0.05) for water (12.1 +/- 0.8), beta-lactoglobulin (14.5 +/- 3.3) and casein (26.5 +/- 9.3). Before ingestion of the test meals, the basal rate of nitrogen was 9.14 +/- 4.09 mmol/h in the jejunum. The total nitrogen content in the jejunum peaked significantly in the 0-20 min period after beta-lactoglobulin ingestion and the 20-40 min period after casein ingestion. The apparent gastro-jejunal protein absorption values were 63% for casein and 66% for beta-lactoglobulin in the 120 min period.


These results show that beta-lactoglobulin and casein behave differently in the upper part of the digestive tract due to different gastric emptying rates.

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