http://www.snopes.com/cokelore/acid.asp

Interesting folklore debunk on Snopes regarding acid in Coke.

I am 38 and began running in May starting with C25K and am now doing 10Ks and training for my first half marathon.  My 15 year old daughter runs track and Cross country, and her team has also stopped drinking soda.  The concerns are calcium depletion, sugars and caffeine.  Diet sodas also tend to make you gain belly weight as the artiicial sweeteners can make you feel more hungry.  I kicked my go to Diet Coke habit (EVERY day at noon had to have it) over 6 months ago now and don"t miss it a bit.  Tea is a way better option if you are a slave to caffeine as many of us are.  Here is a link to an article my daughter's coach posted: http://http://health.yahoo.com/experts/drmao/20270/what-soft-drinks-are-doing-to-your-body/  Good luck!  Hope this helps...

Sondysue,

I'll second anything you do needs to be done in motivation.  I used to drink a lot of diet soda until my husband was convinced the sugar subsitute was the culprit behind my auto immune disease.  I cut back tremendously on my consumption (1 serving a day now usually) and increased my water to compensate...don't see a difference really but feel see better skin condition with the increased water.  Don't know about the running but I'm sure the water hydration is the best for that too.

Cyndi

I don't think a soft drink or two makes a difference.  In fact I run at 4:30 am and if I forget to set the coffee maker I will down a classic coke or two....  I heard some old time runners (Frank Shorter??) would drink FLAT coke before a marathon...  I think for me the issue is that water is just better for me and drinking too many sodas gets in the way of getting in the daily RDA of H2O.

I wouldn't worry about it.  They are empty calories if not diet, though...

BTW I quit drinking all sodas, diet or otherwise for about 6 months.  I recently (last 3 months) started having one or 2 a day again.  I see no affect whatsoever on my times.  Like Len says there is a lot of bad press and scary stuff you can read about aspartame and phenalynine.  If you want a soda I would just go for it in moderation.

No problem I am a fountain of use less err ful information!

I'm pretty skeptical of any new reports of scary new risks (I still own an old Nalgene bottle with BPA, and haven't dropped dead yet!) and I believe NutraSweet and other sweeteners have been studied enough to ensure they're not harmful in the small quantities a typical person would consume. I also used to be a regular Diet Pepsi drinker (2 or 3 cans a day), and about 3 years ago I just got tired of buying it, storing it, finding room in the fridge for it, and recycling the cans afterward. I just quit, and I didn't miss it at all. I still drink coffee with Splenda, though, because I love coffee and enjoy a little caffeine.

However -- and this is why I'm chiming in -- I experienced two very real benefits shortly after quitting the diet soda. First, my chronic tooth sensitivity went away. I had dealt with it for years, even using a special prescription toothpaste. Second, although I had started working out steadily about 6 months before quitting, I had 4 or 5 stubborn pounds that just seemed to hang on. After quitting the soda (and again, I only drank diet), that extra weight came right off, even though nothing else about my routine or diet had changed. I thought it must be my imagination but since then I've read about a study that showed a link between diet soda and weight loss, as though the artificial sweetness or carbonation tricks your body into storing more fat, or something. Who knows why. I can't prove it, but it seemed to match my experience. Now, on the very rare occasion that I have a diet soda at a social event, I feel bloated and uncomfortable afterward.

I can't say whether quitting will help your running performance (I was exercising but not really running back then), but I bet you'll feel better and you'll save a little money too.