Acute effects of nitrate-rich spinach on arterial stiffness in healthy men and women

A randomised controlled cross-over designed study will be performed. Each participant will complete two visits to the University of Western Australia, School of Medicine and Pharmacology located at Royal Perth Hospital. The acute effects on arterial stiffness and blood pressure of two energy-matched (~2000 kJ) meals will be compared. The meals provided at each visit will contain either: (1) 250 mg of nitrate derived from spinach (spinach); (2) <5 mg of nitrate (control). The two visits will be administered in random order, one week apart on the same day and at the same time of day as far as possible. Prior to each visit participants will consume a low nitrate meal for dinner (which will not contain green leafy vegatables or beetroot). Prior to the first visit, participants will document the meal so that they are able to repeat it for the second visit. Each visit will begin in the morning between 08:00 and 10:00 with participants having fasted for at least 12 hours. Baseline measurements will be performed prior to the meal. The meal provided will consist of a white bread chicken and cheese sandwich, with or without 250 g of cooked spinach (255 kJ) containing 250 mg of nitrate. The meal will be consumed over a 15 minute period. Nitrate concentrations in vegetables may vary with season, method of cultivation and storage conditions. To account for this, the spinach will be taken from a single batch of frozen spinach from a commercial supplier, and thawed prior to use. Rice milk (100 mL) will be used as the energy matched low nitrate control for the extra energy provided by the spinach. Outcome measurements will then performed again at specific time points up to 240 minutes (4 hours) post meal.