This study is an extension of a previously published randomised crossover trial.13 The study design was a three-treatment, two- period balanced incomplete block trial, which allows us to get evidence efficiently in a short time scale.14 This study was approved by the Research Ethics Committees of Glasgow Caledonian Uni- versity and University of Strathclyde. This study conformed to the Declaration of Helsinki, and written informed consent was obtained from all participants.