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

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.