Gastric emptying and digestion of whey protein gels

Rationale: Gastric digestion is crucial to food structure breakdown, and subsequent digestion and nutrient absorption. Several studies have shown that protein-rich structured food (i.e. whey protein gel) with higher hardness digests slower during in vitro gastric digestion. However, no in vivo human data are available. In addition, a recent in vitro study showed that the hydrolysis of protein could be monitored by transverse relaxation time (T2), however the feasibility of MRI parameters (T1 and T2) still needs to be investigated in vivo.
Objective:
Primary: To investigate the effect of protein density and texture on gastric emptying of protein-rich solid food.
Secondary: To investigate the use of MRI T2 and T1 of gastric content on indicating protein hydrolysis in stomach.
Study design: Three treatments will be compared in a randomized crossover design.
Study population: 20 healthy adult males
Intervention (if applicable): Participants consume three types of whey protein gels (200 g): 1) low protein density + low hardness, 2) low protein density + high hardness, 3) high protein density + high hardness. MRI abdominal scans, and appetite and wellbeing ratings will be obtained before ingestion and every 10 min until 90 min after ingestion. After the MRI session, satiety will be measured by an ad libitum meal. MRI scans will be used to calculate gastric emptying half-time and MRI T1 and T2 will be used to quantify hydrolysis of protein.
Main study parameters/endpoints:
Primary: Gastric emptying half-time (GE-t50) measured by MRI.
Secondary: Protein hydrolyses will be quantified by MRI T1 and T2 during digestion.
Nature and extent of the burden and risks associated with participation, benefit and group relatedness:
The risks associated with participation are negligible. MRI is a safe and commonly used medical imaging modality. The stimuli consist of normally consumed food ingredients. The burden associated with participation consists of three 2 hours visits, which require an overnight fast and lying in the MRI scanner for 80 min (90 min - consumption time). This may cause minor discomfort. The study is non-therapeutic to the participants.

The higher hardness/protein density of protein gel would delay gastric emptying and protein hydrolysis in humans; MRI technique can used to monitor gastric digestion (in this case: protein hydrolysis) in humans.

Every 10 minutes up to 90 min after ingestion

Participants consume three types of whey protein gels (200 g): 1) low protein density + low hardness, 2) low protein density + high hardness, 3) high protein density + high hardness. MRI abdominal scans, and appetite and wellbeing ratings will be obtained before ingestion and every 10 min until 90 min after ingestion. After the MRI session, satiety will be measured by an ad libitum meal. MRI scans will be used to calculate gastric emptying half-time and MRI T1 and T2 will be used to quantify hydrolysis of protein.