ABSTRACT
Background In vitro studies show that goat milk proteins form less compact coagulates in the stomach compared to cow milk proteins, which may facilitate gastric digestion and amino acid (AA) absorption. However, this has not been confirmed in vivo in humans.
Objective To examine gastric digestion and changes in AA concentrations after cow milk-derived (cow MC) and goat milk-derived casein (goat MC) ingestion.
Methods In this single-blind randomized cross-over study 18 men (age 23 ± 1.6 years, BMI 23 ± 1.6 kg/m2) consumed 300 ml of a drink containing 30 g of cow MC or goat MC. Participants underwent gastric MRI scans at baseline and every 10 minutes up to 60 minutes postprandially. Blood was drawn at baseline and up to 4 hours postprandially. In addition, participants verbally rated their appetite after each MRI measurement. Primary outcomes were gastric emptying and AA concentrations. Secondary outcome was gastric coagulation as inferred by image texture metrics.
Results Gastric emptying half-time was 80 ± 25 minutes for goat and 85 ± 24 minutes for cow MC (p = 0.395). In line with this, gastric emptying of the drinks over time was similar (MD 0.77 ml, 95% CI [-6.9, 8.5], p=0.845). Serum essential AA (MD -110 µmol/L, 95% CI [-162, -58]) was higher over time for cow MC (p<0.001). The image texture metric contrast was lower for cow MC (MD 0.010, 95% CI [0.001, 0.020], p=0.036).
Conclusion Cow MC and goat MC have different coagulating properties, as inferred by AA concentrations and supported by image texture analysis. This did not influence overall gastric emptying or the emptying of the liquid and coagulated fractions, which were similar. This warrants further in vivo research on casein coagulation in the food matrix to help determine the optimal use for cow and goat milk and their protein fractions.
Financial support: the study was funded by Ausnutria Dairy Corporation Ltd.
Clinical trial registry number: NL8137 (Netherlands Trial Registry), accessible through https://trialsearch.who.int/Trial2.aspx?TrialID=NL-OMON28580
Competing Interest Statement
Elise J.M. van Eijnatten: no conflicts of interest Guido Camps: no conflicts of interest Wolf Rombouts: during the study employed as a scientist at Ausnutria Linette Pellis: during the study employed as a scientist at Ausnutria Paul A.M. Smeets: no conflicts of interest
Clinical Trial
NL8137
Funding Statement
This study was funded by Ausnutria.
Author Declarations
I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.
Yes
The details of the IRB/oversight body that provided approval or exemption for the research described are given below:
Ethics committee of Wageningen University gave ethical approval for this work.
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Footnotes
Paul Smeets is associate editor at The American Journal of Clinical Nutrition and played no role in the Journal’s evaluation of the manuscript.
Location of department and institution where the work was performed:
Division of Human Nutrition and Health, Wageningen University, Stippeneng 4, 6708 WE, Wageningen, The Netherlands.
Title, abstract and discussion has been updated.
Data Availability
Deidentified individual participant data that underlie the reported results will be made available upon reasonable request.
List of abbreviations:
- 95% CI
- 95% confidence interval
- AA
- Amino acids
- AUC
- Area under the curve
- BCAA
- Branch chained amino acids
- BMI
- Body mass index
- Cow MC
- Cow milk-derived micellar casein
- EAA
- Essential amino acids
- FFA
- Free fatty acids
- GE
- Gastric emptying
- GE-t50
- Gastric emptying half time
- Goat MC
- Goat milk-derived micellar casein
- MD
- Mean difference
- MRI
- Magnetic resonance imaging
- NEAA
- Non-essential amino acids
- TG
- Triglycerides
- UHT
- Ultra-high temperature processing