BACKGROUND: Gut health relates to a diet with a high digestibility and quality. Limited data are available on the acute effects of low quality foods on gut metabolism and the consequences for liver metabolism. METHODS: A meal with the low quality protein gelatin (tryptophan deficient and low amount of essential amino acids) was compared to a meal with the high quality protein Whey and a tryptophan supplemented gelatin meal (Gel + TRP) in healthy pigs with chronic implanted catheters. In a conscious state, amino acid, ammonia, urea, glucose and lactate fluxes across the portal drained viscera (PDV) and liver were studied for 6 h after administration of the protein meal. RESULTS: The average net portal appearance of amino acids was 99.8 +/- 14.6% of the intake in the Gel group as compared to 61.4 +/- 9.0% (p = 0.022) in the Whey group. In addition, a net portal appearance of tryptophan was observed in the Gel group (p = 0.005) of about 42% of tryptophan released in the Whey group. Intestinal energy metabolism and citrulline production was not affected. Adding tryptophan to the Gel meal diminished net portal AA appearance to 41.6 +/- 24.0% of the intake (p = 0.012), but did not reduce the stimulated liver urea production. CONCLUSIONS: In the post-prandial phase after intake of a low protein quality meal, net anabolism in the healthy intestine is absent. It is likely that the intestine responds with a net breakdown of endogenous (labile) proteins to secure amino acid availability for the body. Addition of the first limiting essential amino acid to this meal improved protein anabolism in the intestine. Protein quality of a meal is related to the anabolic response of the intestine during the meal.