We love answering questions from athletes and one of the things we're asked a lot is how staying hydrated should fit into your wider nutrition (i.e. fuelling) strategy.
Our founder Andy has written a blog to answer a question that recently dropped into the firstname.lastname@example.org inbox...
Q: "You recommend separating out my nutrition and hydration strategies, but can I carry a bottle of carbs and a bottle of electrolytes and switch between the two?"
A: It's a good question and you’re right that we do generally recommend decoupling fuelling and hydration, but the science behind why is not a closed book and sometimes different strategies end up working for different people (or even for the same people in different conditions!).
It’s important to start by saying that the aim is to find a strategy that works FOR YOU, so that should be your focus.
What works for you as an individual is not something that can be figured out entirely theoretically, so this will always ultimately require a decent amount of good old-fashioned trial and error to sort out. Be prepared to try some stuff and to make a few mistakes in order to get to the bottom of your individual case.
That said, the reason we typically suggest getting most of your calories from more solid foods/chews/bars is that this approach results in less overall GI distress for the majority of athletes, especially in the heat or during very long events.
We think this is largely because when you eat solid food and drink your water & electrolytes, your stomach is better able to control the rate that calories move from there into your gut (small intestine), where they are ultimately absorbed into the bloodstream.
This is the case because the food comes together as a ‘bolus’ in the stomach, enabling slower digestion and absorption in comparison to only taking on liquids.
It also enables you to adjust the amount of liquid hydration you take on (highly variable and based primarily on sweat output) separately to the amount of calories you ingest (much more ‘fixed’ based on your size, pace and the upper limit of what you can absorb).
The main issue if you take everything in liquid form is that it can potentially rush into the gut too fast and overwhelm the intestines' capacity to absorb what you are throwing at it. This can lead to discomfort, bloating and even sickness or diarrhoea in some cases.
This is especially true in hot conditions when blood flow to the gut is compromised because you sweat a lot (thus reducing blood volume) and more blood has to go to the skin to help to cool you down. (It might be less of an issue in colder conditions when there is less overall competition for blood flow, so digestion and absorption happens a little more easily in such conditions).
We also think that it is highly relevant that your body naturally tends to crave fluids when you eat food in an attempt to aid digestion (how often do you sit down and eat a normal meal without taking a drink?).
Therefore, when you do take most of your calories via something quite solid you normally get a craving for fluids with it, which is your body's way of trying to balance out the consistency of what you've just ingested in your stomach.
This instinct helps you to drink appropriately based on what your body needs to aid digestion, as well as to maintain hydration status.
The end result of this is a more optimal mix in the stomach and a happier gut overall when compared to drinking a super-concentrated mix in a single bottle.