title: Effects of a 'healthy' diet and of acute and long-term vitamin C on vascular function in healthy older subjects.
abstract: OBJECTIVE
  Aging is associated with endothelial dysfunction. We studied the acute and longer-term effects of vitamin C compared to a 'Mediterranean-type' diet on endothelial function in healthy older subjects.
  
  
  METHODS
  Bilateral venous occlusion plethysmography was used to measure forearm blood flow in subjects aged 57-80 years. Responses to cumulative intra-arterial doses of the endothelium-dependent dilator bradykinin (BK; n=56; 20, 40, 80 pmol/min) and the nitric oxide donor glyceryl trinitrate (GTN; n=54; 4, 8, 16 nmol/min), were determined alone and in the presence of vitamin C (25 mg/min). We then randomised 54 subjects to a 'healthy' diet (n=18), vitamin C (1 g/day; n=18) or placebo for 6 weeks and reassessed endothelial and smooth muscle function.
  
  
  RESULTS
  Acute intra-arterial vitamin C did not alter dilatation to BK or GTN. Similar increases in plasma vitamin C occurred on oral vitamin C (83+/-4 to 135+/-8 micromol/l) and 'healthy' diet (84+/-5 to 135+/-27 micromol/l; P<0.01 for both), with no change seen on placebo. Treatment with a 'healthy' diet but not oral vitamin C improved endothelium-dependent (P=0.043) and endothelium-independent dilatation (P=0.011).
  
  
  CONCLUSIONS
  A 'Mediterranean-type' diet rich in vitamin C improves vascular function. Neither acute intra-arterial nor sustained administration of oral vitamin C improves vascular function in healthy older subjects.
authors.affiliation: Department of Pharmacology and Clinical Pharmacology, St. George's Hospital Medical School, Cranmer Terrace, Tooting, London, UK.
authors.forename: Nivedita
authors.initials: N
authors.lastname: Singh
authors.forename: Jonathan
authors.initials: J
authors.lastname: Graves
authors.forename: Paul D
authors.initials: PD
authors.lastname: Taylor
authors.forename: Raymond J
authors.initials: RJ
authors.lastname: MacAllister
authors.forename: Donald R J
authors.initials: DR
authors.lastname: Singer
mesh_terms: D000284:Administration, Oral; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D019540:Area Under Curve; D001205:Ascorbic Acid / Q000008:administration & dosage* / Q000097:blood; D001920:Bradykinin; D038441:Diet, Mediterranean; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000187:drug effects / Q000502:physiology*; D005260:Female; D005542:Forearm / Q000098:blood supply; D006801:Humans; D007269:Injections, Intra-Arterial; D008297:Male; D008875:Middle Aged; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology; D020030:Nitric Oxide Donors; D005996:Nitroglycerin; D010991:Plethysmography; D012039:Regional Blood Flow / Q000187:drug effects / Q000502:physiology; D018709:Statistics, Nonparametric; D014665:Vasodilator Agents
chemical_list: D020030:Nitric Oxide Donors; D014665:Vasodilator Agents; D005996:Nitroglycerin; D001205:Ascorbic Acid; D001920:Bradykinin