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Dear Thomas,


Many thanks for highlighting these very important points. This is exactly what I reply to those clever people who ask the "bottled water" question completely ignoring water intake from preparing meals and beverages. In most parts of the world even Coke is "local" since only the concentrate is shipped and made up with water at a local bottling plant.

As you rightly say, water intake is more than what we physically drink; most food has a weight% water content no too dissimilar to that of the human body if not higher. So in regions / populations where consumer choice (for whatever reason) favours locally / regionally grown food there is a strong and more direct correlation between isotopic signature of local water and isotopic signature of blood (and urine) and compared to regions/ populations where food may still be sourced from within the same country but from isotopically diverse locations (e.g. North America).

This strong correlation has been exploited for years by scientists interested in total body water and energy expenditure using the labelled (2H) or doubly-labelled (2H and 18O) water method, respectively.

In other words, any erratic or unexpected deviation between isotopic signatures of ingested water and blood (or urine) should prompt one to interogate every step in one's study for potential artefact formation caused by composite isotope abundance values (water plus dissolved organics) or by isotopic fractionation.

As at least one correspondent has already pointed out, water stress (dehydration) and environmental conditions favouring loss of body water can account for this.

In the absence of the above the more likely explanation sadly is fractionation caused by sample storage and sample manipulation, which again has already been mentioned by other list member but cannot be stressed enough.


Best,

Wolfram


________________________________________
From: Stable Isotope Geochemistry [[log in to unmask]] On Behalf Of Thomas L. Millican [[log in to unmask]]
Sent: 18 December 2007 21:19
To: [log in to unmask]
Subject: Re: [ISOGEOCHEM] 2H and 18O values for "blood" water and body tissue

I'd expect a lot of variability between individuals, but there are still a number of water intake sources that are localized besides just drinking water and beer.
As a personal example, every day is started with a cup of coffee made with water from the tap. A bowl of oatmeal or rice is made with water from the tap. Tea is made with water from the tap. For dinner, pasta is made with water from the tap. Even the beer and mead are home-made with water from the tap. I expect that the fruits and vegetables from the local farmer's market are grown with local rainfall similar to the water from the tap. Even if I were to drink bottled water throughout the day when I want just water, there's still a lot of water from the local water supply that I'm taking in.
In places around the world where the local water supply may not be as safe to drink, this may be different to some degree. For example, while living in Bavaria, I found that the tap water would result in undesirable events, so I bought bottled water for drinking and coffee. It would have been  nice to be able to see if there was a shift in O and D in my blood from the moves relative to the local water supplies'.


----- Original Message -----
From: Pier de Groot <[log in to unmask]>
Date: Tuesday, December 18, 2007 2:29 pm
Subject: Re: [ISOGEOCHEM] 2H and 18O values for "blood" water and body tissue
To: [log in to unmask]

> Hi Harro and others,
>
> A lot of good things were mentioned already about the 18O and D
> compositionof human blood. One factor was not mentioned yet, I
> think (or did I overlook
> it?). Some people drink mostly mineral water. If that water
> originates from
> a source different in isotopic composition from the local tap water
> it will
> influence the blood composition too.
> For the Netherlands that would be mostly isotopic compositions as
> found in
> the Belgian Ardennes, or in less cases French or German sources. If
> theinfluence will be significant I am not certain, but maybe good
> to think
> about it.
>
> My two eurocents.
>
> Bets wishes,
> Pier.
>
>
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>
> > From: "H.A.J. Meijer" <[log in to unmask]>
> > Reply-To: Stable Isotope Geochemistry <[log in to unmask]>
> > Date: Tue, 18 Dec 2007 16:32:51 +0100
> > To: <[log in to unmask]>
> > Subject: Re: [ISOGEOCHEM] 2H and 18O values for "blood" water and
> body tissue
> >
> > Thanks colleagues, foor all your reactions and advice.
> >
> > There is a lot to discuss about this subject, that is clear. I am no
> > specialist in this matter, but my intuition that the local water
> must> be key player, is kind of supported through several of the
> comments.> After all, it needs not be water that is directly
> consumed, but water
> > that is conatained in the food (grass, vegetables, even grain
> > contains a large fraction of water that is close to the local
> > Meteoric water). Only under real arid conditions the water produced
> > in the food "combustion" process may play a dominant role.
> >
> > But let me just be more specific about my data.
> >
> > The last two cases I had at hand were wild Cape gannets (South
> > African West Coast and Namibia) and Dutch laboratory mice. First the
> > gannets.
> >
> > I expect their body water to be pretty close to sea water. After
> all,> they eat fish, and fish have no way to escape a VSMOW-like
> imprint on
> > their body water and tissue (seems to me, at least!). And indeed, as
> > far as 18O is concerned, a total of 20 background values of a total
> > of 16 individuals show a de18O of close to zero, with a spread of
> > about +/- 1 per mil. de2H, however, shows about half of the values
> > close to zero, and half considerably above zero (the highest
> being up
> > to almost 100o/oo !).  Looking closer (after the suggestions on
> > Isogeochem) I saw that some of the duplicate mm show one de2H close
> > to zero, and one off by 20-50 per mil.
> > The laboratory mice samples show a similar behaviour: de18O at about
> > -4 per mil (Dutch tap water is around -6 per mil, as well as all the
> > regional vegetation their food is supposedly coming from), de2H at
> > about -25, but with some large excursions to more positive values.
> >
> > So after all, I think Dachun Zhang's observation of some kind of
> > H-exchange in stored blood might be the answer. The samples we
> > process are taken in the field, stored in flame-off glass capilaries
> > and sometimes take many months before they are analysed. The
> analysis> starts with microdistillation, but if exchange has been
> going on
> > before that time, the damage has been done. As it is so variable, it
> > might have something to do with the leaktightness of the capilary?
> > It is something to worry about in the field of Doubly labelled water
> > for energy expenditure, though, since it can just as well affect the
> > labelled samples.
> >
> > Marilyn, as for your nice series of background values on humans, I
> > suggest you contact Klaas Westerterp (university of Maastricht,
> > Netherlands, <[log in to unmask]>), who has an impressive
> > track record of using DLW techniques on humans. My guess is he is
> > interested, and he can tell you in how far your series contains
> > unique material.
> >
> > Thanks once more, and if anyone has a concrete idea about a possible
> > exchange process, I'll be eager to know.
> >
> > Harro
> >
>