The purpose of this study is to determine whether dietary nitrate supplementation improves performance in cardiopulmonary exercise testing (CPET).

Dietary nitrate supplementation has been shown to enhance exercise tolerance and performance in professional athletes and physically active males.

Cardiopulmonary exercise testing (CPET) is an established, non invasive and safe method of assessing patients' cardiopulmonary reserve prior to surgery. It has been shown to predict complications and length of stay in patients undergoing major elective surgery.

The anaerobic threshold (AT), the oxygen uptake at which anaerobic ATP synthesis supplements aerobic ATP synthesis and the maximal oxygen uptake (VO2max) the point where the oxygen uptake plateaus despite an increase in work rate; both calculated during CPET; have both been shown to predict short and long term outcomes after surgery and postoperative complications.

We aim to study the effect of dietary nitrate supplementation on CPET results in patients awaiting surgery for colorectal cancer.

Our primary outcome will be the change in the AT and VO2Max after beetroot juice supplementation.

Methods: Patients will undergo an initial CPET and will then be randomized to receive either beetroot juice (BRJ, containing NO3-, 6.2 mmol/day, administered as 500ml Beet it Sport Shots, James White drinks, Ipswich uk) or 'placebo' (PL, NO3-depleted beetroot juice) for 7 days. A second CPET will then be performed.

This pilot study will be used to calculate the mean AT and VO2Max and associated standard deviations for our population and the approximate effect of BRJ on them.

Inclusion Criteria:

• Elective Colonic or rectal resection.

Exclusion Criteria:

• Contraindication to cardiopulmonary exercise testing: unstable cardiac disease, lower limb dysfunction, inability to perform CPET
• Inability to give informed consent
• Emergency surgery
• During CPET: Ischemic ECG or inability to reach AT
• Allergy to Beetroot