Why aren't there studies on whether hydration treats colds?
Everyone says hydration is important to treat colds:
“Drink plenty of water,” says the UK’s National Health Service
“Stay hydrated,” says Mayo Clinic
“Stay well hydrated,” says the New York Times
“Drink a Ton of Water,” says Fox News
So you’d think there would be some randomized controlled trials on this. But in 2004, the BMJ published an (attempted) review of the RCTs - “Drink plenty of fluids”: a systematic review of evidence for this recommendation in acute respiratory infections:
We found no randomised controlled trials comparing increased and restricted fluid regimens in patients with respiratory infections.
I couldn’t find any studies since 2004. In 2018, the BMJ listed “Fluid Intake” under “No evidence of effect” in a publication about treating colds.
Why aren’t there any RCTs on this?
I get that water isn’t patentable and studies are expensive, so who will fund it? But people do occasionally study treatments that aren’t drugs. It seems like a reasonable enough thing for someone to want to study. Either you confirm the folk wisdom, and then you get mentioned whenever a serious (i.e. study-linking) publication wants to publish advice on colds, which happens every day. Or you disconfirm it, and maybe get some headlines, probably some controversy but more the makes-you-notable than ruins-your-life kind.
Are grant-makers are the limiting factor? Maybe hydration for colds is so obvious and well-known that they decide they’re better off funding something more useful.
