Effect of Betaine, Serine and Folic Acid on Vascular Function in Healthy Volunteers

Inclusion Criteria: * Apparently healthy * Women postmenopausal: two or more years after last menstruation. If the uterus was surgically removed, the women must be 55 years or older * Normal blood values for: hematology, total homocysteine, lipids, vitamin B6, vitamin B12, folic acid, liver enzymes, creatinine * Absence of protein and glucose in urine sample * Body mass index (BMI) between 18 and 30 kg/m2 * Good ultrasound visibility of the brachial artery, judged by a sonographer. * Willing not to use supplements containing B-vitamins, antioxidant vitamins (A, beta-carotene, C and E) or n-3 fatty acids/fish oil supplements from screening day (\>2 months before start of the study) until end of study * Willing not to be blood or plasmapherese donor from 4 weeks before the screening day, and 4 weeks before the start of the study until the end of study Exclusion Criteria: * Any chronic or acute disease (e.g. diabetes, renal disease, inflammation) * Current, or history of cardiovascular disease * Hypertension * Medical history or surgical events know to interfere with the study * Fasting plasma total homocysteine \> 26 micromol/L * Alcohol consumption: women \>21 consumptions/week; men \>28 consumptions/week * Weight loss or gain \> 2 kg in the month prior to screening * Any special diet (prescribed, slimming, macrobiotic or total vegetarian. Sole exclusion of meat and fish from a otherwise 'normal' western diet is allowed). * Lactose intolerance * Use of supplements containing B-vitamins more than once weekly in the period from 3 months before the screening day * Participation in any other trial up to 3 months before this study * Use of medication known to interfere with the study outcome.