Effect of Betaine and Folic Acid on Vascular Function in Healthy Humans

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, blood lipids, vitamin B6, vitamin B12, folate, 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 the 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 plasmapheresis 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 known to interfere with the study. * Fasting plasma total homocysteine \> 26 micromol/L. * Alcohol consumption: more than 21 consumptions /week for women, and more than 28 consumptions/week for men. * 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 an 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.