<< Cross Country coach (also biology teacher) told us that that the CO^2 in pop would sometimes bind to the red blood cells instead of oxygen. Basically, the CO^2 would reduce the blood cells ability to carry oxygen. >>
Unfortunately, what your coach failed to mention that CO2 is routinely carried by the RBCs in your body and is exchanged for O2 in the lungs. CO2 has NO "special" affinity for binding with RBCs over O2......basically, he's full of it. The only harm the CO2 would do to you is irritate your stomach lining if you have/are developing an ulcer. Possible there could be a slight alteration in your pH of your blood, but the buffering system in your body automatically stabilizes that.
Now, take carbon monoxide, or CO, that has a binding effect on the hemaglobin component of the RBC and will stay with the RBC until it dies.
As far as caffeine and dehydration in soda, caffeine is a mild diuretic, and the amount found in Coke, very small amts., is not enough to make your body get rid of all the water taken in when you drink a Coke, which is about 98% water. The "fact" that sodas dehydrate you is another fable. In fact, a new study just being published in the JAMA revisits just this issue....water vs. soda intake, and their conclusion was that soda, except for stuff like Jolt, can count as part of your dialy intake of water.
The sugar, which is in a fairly simple carbohydrate form in soda, is rapidly absorbed in the stomach and duodenum...the only danger this poses is if you are unable to process sugar well, ie. diabetic, or the danger of rotting your teeth out. Otherwise, it's just empty calories.
My knowledge bade? I'm an RN with over 20 years practicing.......have credentialing in critical care and ER. Have taken lots and lots of anatomy and physiology courses over the years, and I'm continually amazed at the hokum that's put out as fact.
Peace.