Footnotes

• Contributors ES conducted the search of the retailer websites and wrote the first draft of the manuscript. JGLL and DJ provided critical review on the manuscript. All authors approved the final version of the manuscript.

• Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

• Competing interests None declared.

• Patient consent for publication Not required.

• Provenance and peer review Not commissioned; externally peer reviewed.