The purpose of this study is to elucidate whether bitter taste induced by the bitter compound caffeine and the reduction of bitter taste by addition of the bitter masking compound Homoeriodictyol sodium salt (HED) influence gastric acid secretion, subjective feelings of hunger, ad libitum food intake and satiating hormones in healthy volunteers.

The influence of 125 mL water, 150 mg caffeine/125 mL water, 30 mg HED/125 mL water or the combination of 150 mg caffeine + 30 mg HED/125 mL water on the gastric pH on different test days was investigated. Prior to the intervention, the trial subjects had to fast from food and liquid for 10 h, except for 200 mL of tap water that were allowed during this time period. During the experiment, the subjects remained in a supine left-sided position.

For the non-invasive measurement of the gastric pH, the Heidelberg Detection System (Heidelberg Medical Inc., USA) was used which has been successfully used in our working group.

This system consists of a pH-sensitive capsule (called a Heidelberg capsule), with a length of 2 cm, that has to be swallowed and contains a miniature radio transmitter. This system allows the detection of the actual gastric pH of the volunteer over a specific time period [Liszt et al 2012, Rubach et al. 2014].

Prior to each test, Heidelberg capsules were activated for 5 min in a 0.9% sterile NaCl solution and calibrated using two calibration points, pH 1 and 7. Afterward, the subjects swallowed the capsule lay down on the left side. The capsule sends a signal to a transceiver, which has to be placed on the abdomen of the volunteer. The transceiver sends the signal to the recorder connected to a computer. The data can be collected and shown as a gastrogram on the computer screen, where the pH is drawn over time. When the intragastric pH was constant between pH 0.5 and 2.5 for at least 3 min, the capsule was considered to be in the stomach. Afterward, each trial started with the administration of 5 mL of a saturated sodium bicarbonate solution (NaHCO3). This alkaline challenge triggers a rise in gastric pH between around pH 6 to 7 and subsequently leads to the secretion of stomach acid by the parietal cells. The test solutions were administered 5 minutes after or 30 min before the alkaline challenge.

Reacidification time as well as the time until start of the reacidification has been analyzed.

Ratings of hunger were assessed before and after each gastric pH measurement by means of visual analog scales (VAS). Before and after each intervention blood samples were drawn to quantify satiety hormones (ghrelin, PYY, GLP-1, serotonin). Ad libitum energy and macronutrient intakes from a standardized breakfast served after each treatment were calculated.

Inclusion Criteria:

• good general state of health
• sensorically untrained
• BMI: 19 - 26 kg/m2

Exclusion Criteria:

• gastro-intestinal disease or discomfort,
• metabolic diseases,
• H.pylori infection,
• smoking,
• increased sensibility towards caffeine,
• intake of antibiotics in the last 2 months,
• medication except for oral contraceptives,
• drug- or alcohol-abuse,
• heart disease, high blood pressure,
• pregnancy