Effect of Oral Lubrication on Appetite, Food Intake and Salivary Biomarkers in Protein Beverages

Effects of Protein Beverages Differing in Their Lubricating Properties on Appetite Control, Subsequent Food Intake and Salivary Biomarkers

The main aim of this study is to elucidate the influence of protein beverages differing in their lubrication properties (low/medium/high lubricating) and control (water) on satiety and satiation.

The researchers propose an acute, randomized cross-over study that compares three types of protein beverages differing in their lubricating properties, i.e. one with low lubricating properties made using sodium caseinate, one with medium lubricating properties made by whey protein, and the third one with high lubricating properties made by heated whey protein. All three beverages contain added banana flavour and non-nutritive sweetener. Water acts as a control and has the same flavour and sweetness to match those of the protein beverages.

Participants are asked to come to the laboratory on four occasions. Before participating, each participant is screened for eligibility criteria using an online health screening questionnaire and Three Factors Eating Questionnaire. Participants are offered one of the four treatments (water or either of the three protein beverages), the order of which is randomized and counterbalanced.

Participants are instructed to fast for 11 hours and to restrict from drinking alcohol for 24 hours before each session. Each session lasts 1.5 hours (8.40 am until 10.10 pm). In the first session, weight and height are measured. Participants then provide baseline (- 5 min) appetite ratings on a 100 mm visual analogue scale (VAS). After that they are given the preload - either protein beverages differing in their lubricating properties or water. Then, participants are asked to rate their appetite on a 100-mm VAS every 10 minutes for the next 30 minutes. Ad libitum food is offered as breakfast after 30 min after ingesting the preload and the last VAS is taken. Saliva is taken three times during each session before preload, after preload consumption and before ad libitum breakfast.

Inclusion Criteria:

• Adults aged 18-55 years old
• With a BMI between 18.5 - 27.99 kg/m²)
• Generally healthy

Exclusion Criteria:

• have any blood borne disease;
• have type-1 or type-2 diabetes;
• have liver and kidney disease;
• have past history of gastrointestinal surgery;
• are a smoker;
• have oral infections/ diseases;
• have chronic or acute health condition that may affect ability to sense, eat, digest, absorb or excrete food;
• have a sensitive stomach (Irritable Bowel Stomach);
• are currently using prescribed or non-prescribed medication;
• are pregnant or lactating;
• are suffering from an illness, feeling unwell, having fever, or cold or cough;
• history of food allergy or intolerance;
• are on any special diet or are taking protein and/or fibre supplements;
• cannot tolerate protein beverages;
• present any COVID related symptoms (high temperature, a new continuous cough, a loss or change to your smell or taste);
• if you are self-isolating or if you leave with someone self-isolating or presenting COVID related symptoms.