Prospective, open, mono-center, randomized, two part study with 4-way cross-over design in each study part.

The objective of the study is to investigate blood glucose levels after oral intake of defined amounts of lactulose.

Inclusion Criteria:

• Healthy volunteers
• Age: 18-65 years
• Approx. 3-5 bowel movements per week
• Caucasian
• Availability and presence in the trial unit for approx. 4 hours/ week for 4 times in a row with approx. 1 week of washout in between
• Signed informed consent form

Exclusion Criteria:

• Known (family) history of diabetes mellitus or use of anti-hyperglycaemic drugs or Insulin
• Clinically relevant renal or hepatic disease, liver enzymes > 10% above reference range
• Fasting blood glucose > 100 mg/dL or HbA1c outside of reference range
• Total cholesterol > 250 mg/dL or triglycerides > 150 mg/dL
• Haemoglobin < 11 g/dL (women); < 12.5 g/dL (men)
• BMI < 19 kg/m² and ≥ 30 kg/m²
• Intentional and unintentional weight loss > 5% in the previous 6 months
• Smoker
• Major medical or surgical event requiring hospitalization within the previous 3 months
• Presence of disease or drug(s) influencing digestion and absorption of nutrients or bowel habits
• Intake of medications known to affect glucose tolerance, e.g., steroids, protease inhibitors or antipsychotics (stable doses of e.g., oral contraceptives, thyroxin, vitamins and mineral supplements or drugs to treat hypertension or osteoporosis are acceptable)
• Chronic intake of substances affecting blood coagulation (e.g. acetylic acid, anticoagulants, diuretics, thiazides), which in the investigator's opinion would impact volunteer safety
• Hereditary problems of galactose or fructose intolerance, lactase deficiency or glucose-galactose malabsorption
• Suspicion of drug abuse
• Abuse of alcoholic drinks, defined as an average daily intake of more than one litre of beer per day or equivalent amount of alcohol in other beverages
• Pregnant or breast feeding women
• Known or suspected allergy to any component of the investigational product(s)
• Known HIV-infection
• Known acute or chronic hepatitis B and C infection
• Blood donation within 4 weeks prior to visit 1 or during the study
• Volunteer unable to co-operate adequately
• Participation in a clinical trial with an investigational product within one month before start of study