Intraileal casein infusion increases plasma concentrations of amino acids in humans: A randomized cross over trial

D. Ripken*, M.H. van Avesaat, F.J.J. Troost, A.A. Masclee, R.F. Witkamp, H.F.J. Hendriks

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review


BACKGROUND: Activation of the ileal brake by casein induces satiety signals and reduces energy intake. However, adverse effects of intraileal casein administration have not been studied before. These adverse effects may include impaired amino acid digestion, absorption and immune activation. OBJECTIVE: To investigate the effects of intraileal infusion of native casein on plasma amino acid appearance, immune activation and gastrointestinal (GI) symptoms. DESIGN: A randomized single-blind cross over study was performed in 13 healthy subjects (6 male; mean age 26 +/- 2.9 years; mean body mass index 22.8 +/- 0.4 kg/m-2), who were intubated with a naso-ileal feeding catheter. Thirty minutes after intake of a standardized breakfast, participants received an ileal infusion, containing either control (C) consisting of saline, a low-dose (17.2 kcal) casein (LP) or a high-dose (51.7 kcal) of casein (HP) over a period of 90 min. Blood samples were collected for analysis of amino acids (AAs), C-reactive protein (CRP), pro-inflammatory cytokines and oxylipins at regular intervals. Furthermore, GI symptom questionnaires were collected before, during and after ileal infusion. RESULTS: None of the subjects reported any GI symptoms before, during or after ileal infusion of C, LP and HP. Plasma concentrations of all AAs analyzed were significantly increased after infusion of HP as compared to C (p < 0.001), and most AAs were increased after infusion of LP (p < 0.001). In total, 12.49 +/- 1.73 and 3.18 +/- 0.87 g AAs were found in plasma after intraileal infusion of HP and LP, corresponding to 93 +/- 13% (HP) and 72 +/- 20% (LP) of AAs infused as casein, respectively. Ileal casein infusion did not affect plasma concentrations of CRP, IL-6, IL-8, IL-1beta and TNF-alpha. Infusion of HP resulted in a decreased concentration of 11,12-dihydroxyeicosatrienoic acid whereas none of the other oxylipins analyzed were affected. CONCLUSIONS: A single intraileal infusion of native casein results in a concentration and time dependent increase of AAs in plasma, suggesting an effective digestion and absorption of AAs present in casein. Also, ileal infusion did not result in immune activation nor in GI symptoms. CLINICALTRIALS.GOV: NCT01509469.
Original languageEnglish
Pages (from-to)143-149
Number of pages7
JournalClinical Nutrition
Issue number1
Publication statusPublished - Feb 2017


  • IIeal brake
  • Protein
  • Amino acid absorption


Dive into the research topics of 'Intraileal casein infusion increases plasma concentrations of amino acids in humans: A randomized cross over trial'. Together they form a unique fingerprint.

Cite this