So I shouldn't be drinking straight water on a long ride- everything should have a little sports drink mixed in?
Here's Dean's response:
Regarding electrolytes, let me start by saying that you are obviously doing something right, given your long-distance riding successes. Any deviations from something that already works should be tested first on training rides.
Drinking straight water on rides lasting longer than two hours is fine if one eats real food, which generally supplies not only the right minerals but the right amounts. Cyclists normally obtain food on brevets, since meal breaks are often customary. Sufficient alternatives to food (for mineral content) include special energy powders and electrolyte tablets. On the other hand, sports bars, gels, and drinks do not always supply either the full array of minerals long-distance cyclists require or the amounts/ratios required for easy assimilation.
In addition to the essential minerals they provide, food and specially formulated energy powders have the added benefit of supplying easily assimilable calories. Such nutriment has the added benefit of promoting the burning of stored fat, which accounts for more than half the energy used by distance cyclists.
On long rides, the body unavoidably uses protein as yet another energy source. If a cyclist’s on-the-bike diet includes some protein, then the body not only has another readily available energy source but is less likely to scavenge muscle.
If a cyclist eats a disproportionately high amount of simple sugar(s), then the desirable fat-burning process may be hindered. Also, a huge meal forces the digestive system to compete with muscles for blood.
In conclusion, although it is oftentimes necessary to discuss electrolytes irrespective of hydration and food requirements, in devising a suitable strategy for replenishing electroylytes, it is helpful to view the latter as part of an integrated food and hydration plan.