The results of our in vitro studies strengthen the hypothesis that the contribution of salivary alpha-amylase to starch digestion has been underrated and that this enzyme can play an important role in this process. As a result, its inhibition could constitute an opportunity to reduce the glycemic response elicited by starch-rich foods. The main goal of this study is to verify whether inhibiting salivary alpha-amylase upon the consumption of starchy foods, can have an impact on the postprandial glycemic response, and/or satiety.

The main objective of this work was to test the impact of adding black tea or lemon juice to a starch-rich meal on postprandial plasma glucose concentrations and on energy intake in healthy humans. This study was divided into two parts.

The objective of part 1 was to determine the effect of pairing a starch-rich food with water, black tea or lemon juice on postprandial plasma glucose and energy intake in healthy humans. This study was conducted in semi-controlled conditions. The three test meals (equal portions of bread (100 g) and 250 mL of either water, black tea or lemon juice) were consumed as breakfast (after a 10-h fast) on independent days and in a randomised order. Capillary blood glucose concentrations were self-monitored using the finger-prick method at pre-defined time-points during 180 min. Ad libitum energy intake was assessed 3 hours later.

The main objective of part 2 was to investigate whether the gastric emptying patterns remain, or not, the same when a bread meal is paired with water, tea, and lemon juice. Blood glucose response and satiety perceptions were also monitored. The test meals were similar to those in branch 1, except that the meals were supplemented with 20 peas, which the subjects were asked to swallow at the end (with half of the beverage provided) without chewing. These peas conferred a distinct contrast in MRI scans and could be used as stomach motility and gastric mixing tracers in MRI images. Capillary blood glucose concentrations were determined using the finger-prick method at pre-defined time-points during 180 min. Visual analogue scales were used to assess satiety-related perceptions.

Volunteer recruitment was conducted independently for each part of the study and volunteers were allowed to participate in one part of the study only. Data collected in each part of the study was analysed independently.

Inclusion Criteria:

• To be overall healthy
• To be between 18 and 60 years old
• BMI between 18 and 25 (lean)
• No eating disorders
• No major weight changes (> 3kg in previous 3 months)
• Structured eating habits (3 main meals/day, everyday)
• Not using corticoid drugs, or antidepressives known to influence food consumption, appetite and/or mood.
• Not using medication known to influence glucose tolerance: acetylsalicylic acid or thyroxin, vitamin or mineral-based dietary supplements, and drugs to control hypertension or osteoporosis are acceptable
• No allergies to the foods in the test-meals and ad libitum meal
• No abusive alcohol consumption
• No intensive exercising habits
• No participation in a clinical study within the previous 6 months
• To enjoy the foods in the test-meals and ad libitum meals
• To be affiliated to a social security system
• To be available to participate in study sessions
• To have read and signed the Informed consent form

Additional criteria for Part 2

• Male
• Ability to be in an MRI scan without moving
• Ability to hold breath for 25s (a requirement for certain MRI exams)

Non-inclusion criteria:

• History of diabetes, use of antihyperglycemic drugs or insulin to treat diabetes or associated conditions
• Major medical interventions or surgeries requiring hospitalization within the previous 3 months
• Any medical condition that affects digestion and/or nutrient absorption
• Use of steroids, protease inhibitors and/or antipsychotic drugs
• Use of anticoagulation drugs
• To be participating in another clinical trial, or to be within the exclusion period of a previous clinical trial
• To have started or stopped smoking within the previous 3 months

Additional exclusion criteria for Part 2:

• Any contraindications to an MRI exam: claustrophobia, tatoos, presence of ferromagnetic elements, having a pacemaker, metallic prosthesis, cochlear implants, vascular clips, insulin pumps
• Any condition or disease that might affect the results of MRI exams.