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The UK newspaper the Daily Telegraph has reported that the European Union won't permit claims that drinking water will prevent dehydration, saying that there's no evidence supporting the claim.

Is there scientific evidence supporting the benefit of dihydrogen monoxide for this purpose?

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    The first question should be: "is the EU actually saying what the article reports?" -- the source is a known anti-EU group, in an anti-EU paper, in an anti-EU country... – Sklivvz Nov 24 '11 at 8:31
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    I've taken a look at the actual EFSA statement and it's quite different... They simply say that ads on mineral water bottled can't say that their product reduces the risk of dehydration. Which is in fact a false statement as dehydration occurs anyways. It's a pronunciation against weasel commercials, not anti-science... – Sklivvz Nov 24 '11 at 9:13
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    You need to read the claim in the context of a widespread habit of anti-EU newspapers to make stuff up to make the EU look ridiculous. As far as I remember the curved banana and cucumber story is one of those but in this source is simply reported as acknowledged fact. I would be as cautious as @Sklivvz . – matt_black Nov 24 '11 at 9:18
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    @Sklivvz: And assuming for the sake of argument that the Telegraph report was false or misleading - isn't it good its claim has been mentioned here so people can debunk it? – Andrew Grimm Nov 24 '11 at 9:23
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    @andrew sure, in fact I am suggesting that you change the wording to reflect that. Also note that the answers also point out the same as my comment, but do not exactly answer your question... – Sklivvz Nov 24 '11 at 9:30
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My interpretation on this story is that it is simply a confusion of meaning.

If you do not drink any water for a long period, you will get dehydrated.[Ref] Drinking water will help remedy that. [Ref]

However, there are many causes of dehydration, including especially diarrhea, but also other causes such as vomiting, diabetes and burns. [Ref.]

It is false to state that drinking water will prevent ongoing dehydration due to these causes. In fact, it may be appropriate to take other "clear fluids" orally to address the dehydration, e.g. containing electrolytes or even IV drips may be required. [Ref]

My interpretation is that this claim - that water can prevent dehydration - is what the EU declined to approve. Dehydration may occur even when normal levels of water have been consumed.

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The European Food Safety Authority (EFSA) which evaluates those claims has published a report on their decision.

Scientific Opinion on the substantiation of health claims related to water and maintenance of normal physical and cognitive functions (ID 1102, 1209, 1294, 1331), maintenance of normal thermoregulation (ID 1208) and “basic requirement of all living things” (ID 1207) pursuant to Article 13(1) of Regulation (EC) No 1924/2006

They conclude for the first claim:

The claimed effects are “hydration, e.g. body function, physical and cognitive performance”, “adds to fluid intake and supports hydration”, and “hydration”.

[...]

  • A cause and effect relationship has been established between the dietary intake of water and maintenance of normal physical and cognitive functions.

  • The following wording reflects the scientific evidence: “Water contributes to the maintenance of normal physical and cognitive functions”.

This means that you can advertise the mentioned claim on water bottles you're selling. In the appendix they list for claim 1331 the wording "water keeps you hydrated", which is pretty much what was mentioned in the article.

For the third claim, that water is a basic requirement for all living things, they concluded

The claimed effect is general and non-specific, and does not refer to any specific health claim as required by Regulation (EC) No 1924/2006

I'm not sure if that means you cannot advertise that or that it isn't a medical claim and it doesn't fall under the regulations.

There probably is more history to the whole thing, I could imagine that there were some disputes about the exact terminology. The document is published in April 2011, so it was available when the article in your question was published.

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