Exogenous and endogenous nitrogen flow rates and level of protein hydrolysis in the human jejunum after [¹⁵N]milk and [¹⁵N]yoghurt ingestion

Abstract

Milk and yoghurt proteins were I5N-labelled in order to measure the flow rate of exogenous N during digestion in the human intestine. After fasting overnight, sixteen healthy volunteers, each with a naso- A great difficulty in the study of intestinal protein digestion in humans arises from the fact that after ingestion, dietary proteins are mixed with endogenous proteins secreted in the lumen, i.e. gastric, bilio-pancreatic and intestinal secretions. In addition, contrary to fasting conditions where endogenous proteins are continuously secreted into the lumen at a constant level (Gaudichon et al. 1994a), the ingestion of a meal stimulates salivary, gastric and bilio-pancreatic secretions (Alpers, 1987) to a level which depends on the amount and on the nature of the meal and particularly its dietary protein content (Lurie et al. 1973;Girard-Globa et al. 1980;Simon et al. 1983

Portal absorption of 15N and amino nitrogen in the growing pig after ingestion of labelled milk, yogurt or heat-treated yogurt

“…This result is undoubtedly related to the different intestinal emptying rates between milk, yogurt and heat treated yogurt as has been suggested by several authors [7,8,33,35]. Since the viscosity differences between milk and live yogurt result in a slower gastric emptying rate for yogurt [33], it is understandable that the portal absorption profile of 15 N and AN is for live yogurt (Y0 and Y21) when compared to M and HY.…”

“…Thus storage of yogurt at 4 °C did not modify the nutritional characteristics of yogurt. disappearance (ingested minus recovered exogenous nitrogen) in the lumen [7,8]. These authors particularly noticed that the highest exogenous jejunal nitrogen contents were measured 20 min after milk ingestion and 60 min after yogurt ingestion.…”

“…Recently, the use of 15 N labelled milk proteins made it possible to distinguish exogenous from endogenous N fractions in the human intestine after 15 N milk or 15 N yogurt ingestion [8]. These authors pointed out that 15 N nitrogen jejunal flow was different for milk and yogurt.…”

“…Since stable isotopes are suitable to distinguish the exogenous from the endogenous protein fraction in the intestinal lumen, intrinsic isotopic labelling of milk proteins has been considered as one of the most interesting techniques for nutritional studies [8,9,17]. Recently, the use of 15 N labelled milk proteins made it possible to distinguish exogenous from endogenous N fractions in the human intestine after 15 N milk or 15 N yogurt ingestion [8].…”

The challenge of diabetes in Asia

“…This NPPU method has been applied to a variety of different protein foods (Bos et al, 1999(Bos et al, , 2005(Bos et al, , 2007Gaudichon et al, 1995;Gausserès et al, 1997;Lacroix et al, 2006Lacroix et al, , 2008Mariotti et al, 1999Mariotti et al, , 2000Mariotti et al, , 2002). True ileal nitrogen digestibility measured for different protein sources were: milk protein, 95% Gaudichon et al, 2002;Mahé et al, 1994b); soya and pea protein, 91 % Gaudichon et al, 2002;Gausserès et al, 1997); wheat protein, 85-90% (Bos et al, 2005;Juillet et al, 2008); rapeseed protein, 84% (Bos et al, 2007).…”