Cognitive and Cerebral Blood Flow Effects of Vitamin C

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.

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.

• Endothelial Function
• Cognition

• Placebo Comparator: placebo
  Intervention: Dietary Supplement: Vitamin C
• Experimental: Vitamin C
  Intervention: Dietary Supplement: Vitamin C

Inclusion Criteria:

• Male/Female,
• 18-35

Exclusion Criteria:

• Smokers,
• not proficient in English,
• are (or are seeking to become) pregnant, are currently taking illicit,
• over the counter/prescription medication (including the contraceptive pill),
• and/or dietary/herbal supplements.
• Food allergies or sensitivities that are relevant to the study,
• a history of/current head trauma,
• learning difficulties,
• ADHD and
• migraines.