Cognitive and Cerebral Blood Flow Effects of Vitamin C
Condition: Endothelial Function; Cognition
Study type: Interventional
Phase: Phase 4

Summary: 
      This investigation is interested in the effects of high dose vitamin C on endothelial
      function in healthy humans. A high fat meal will be utilized to induce endothelial
      dysfunction. It is hypothesized that, via antioxidant actions, vitamin C will reverse these
      effects and in turn improve blood flow- the involvement of nitric oxide suggests that this
      could extend to cerebral blood flow. This will be monitored by trans cranial doppler flow
      meter and near infrared spectroscopy.
    

Detailed description: 
      The acute effect of administering vitamins has received little research attention. The
      exceptions are a number of studies that have observed that single doses of a variety of
      vitamins, including Vitamin C, E and several B vitamins, ameliorate endothelial dysfunction
      in the periphery in participants who smoke, or suffer disorders such as diabetes mellitus and
      cardio-vascular disease. Endothelial function also varies in healthy people as a consequence
      of diet, and it is possible that antioxidant vitamins can attenuate the vaso-constriction
      associated with commonly consumed foodstuffs. Indeed, a study by Title et al (2000) showed
      that vitamin C improved endothelial function in the forearm following a glucose drink. Given
      the putative underlying mechanisms involved (e.g. nitric oxide synthesis) any improvement may
      well also extend to cerebral blood flow (CBF), and therefore improvements in aspects of
      cognitive function.

      The study will therefore assess the effects of a single dose of 1000 mg of vitamin C on
      cognitive performance and cerebral arterial blood flow velocity (cBFV) using Trans-cranial
      Doppler, following a high fat meal that has been used in previous endothelial function
      research.

      The high fat meal will be administered 2 hours before testing begins. Research shows that a
      meal of this type produces effects on the endothelium which are similar to those induced by
      dysfunctions such as diabetes i.e. blood flow restriction. No adverse effects have been
      reported with regards this methodology however.

      In order to monitor the effects of vitamin C (or not in the case of placebo) on endothelial
      function and cerebral blood flow near infrared spectroscopy (NIRS) and trans cranial Doppler
      (TCD) recordings will be taken throughout (in the case of the former technique) and at
      intermittent stages (in the case of the latter). Both neuroimaging modalities, when used
      correctly) are entirely safe. Blood pressure readings will also be taken intermittently
      throughout testing sessions.
    

Intervention name(s): Vitamin C
Intervention type(s): Dietary Supplement
Intervention description(s): Vitamin C will be administered at a dose of 1000mg. There will be at least a 48 hour wash out period between both conditions (placebo and vitamin C), with the order dicteted by Latin square.
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: Double (Investigator, Outcomes Assessor)
Primary purpose: Basic Science
Keywords: Vitamin C; Cognitive performance; Cerebral blood flow; Trans cranial doppler; Near infrared spectroscopy