This is a great article, if you haven't already seen it.  It is a great example of how we need to be skeptical of the diet and nutrition information that is fed to us (get it?  Fed to us?) on a regular basis via the media, and to read and understand the specifics of any research study.

http://io9.com/i-fooled-millions-into-thinking-chocolate-helps-weight-1707251800

" Fed to us?) on a regular basis via the media"...

I will NEVER forget when I yelled so loud and so long in a WW meeting because they taught "DIET SODA IS HYDRATING"

Yep.

I almost crapped myself.  For years, nutritionists tell us it is dehydrating due to the salts, caffeine and artificial sweeteners.  

Then they came out with a food company and said "It contains water, therefore it is hydrating." 

I still kick myself for not quitting that day.

I was so stupid... I mean if they are wrong in promoting that...what else is wrongfully being promoted?

But nooooo...I just said "Ok. Whatever" and kept falling "the plan" and forking over my hard earned money.

Sometimes, I really have problems with respecting the past "me" and her previous decisions.

Live and learn.

Of course it's hydrating. Why wouldn't it be hydrating? It used to be an oft-told myth that caffeine is dehydrating, but that's been proven wrong. There are artificial sweeteners in lots of other things. And the amount of salt in a diet soda isn't enough to make an impact.

I'm not saying diet soda is the best thing for you. But it certainly is hydrating.

They are not wrong.  Whatever nutritionists (who frequently have no health degree of any kind, BTW) you were listening to are.

The vast majority of diet sodas have NO salt (Check the ingredients for yourself) or VERY little (as a preservative) and, as Grim already said, the idea that caffeine was a diuretic has been disproven.  It was based on a single, flawed study and has been contradicted by several more recent studies.

Lora

p.s. Diet 7-Up (I had half of one this evening) has 25mg of sodium (which is HALF the amount of sodium in a teaspoon of mustard or catsup).  So it isn't quite zero, but is insignificant.

I've got to ask, since I've been wondering for a while, are you actually a scientist?  What is your field of research?  

i really am.  I am a pharmacologist.  I specifically developed a phenotypic test to determine how rapidly on metabolizes their 5-FU chemotherapy.

Fyi - salt is essential in keeping water in our body, 

I have to add salt to my food all the time. 

I drink diet tonic all the time. Really helps me staying hydrated. 

Ohhhh... diet tonic, I forgot about that. Is it OK to add gin and lime to cut down on the carbonation?

Hell yea... Why not?