The following clinicians contributed to this briefing:
Kevin Barrett, general practitioner. Dr Barrett has received honoraria for attending advisory boards for Yakult and Tillots, and payment for speaking at events by Ferring. He is also the chair of the Primary Care Society for Gastroenterology.
Andrew Poullis, consultant gastroenterologist, St George's Hospital London, did not declare any conflicts of interests.
Justin Roe, joint head of speech and language therapy at the Royal Marsden Hospital and clinical service lead in airways/laryngology at Imperial College Healthcare NHS Trust, did not declare any conflicts of interests.