Fancy working up a sweat? You’d better duck into the corner shop, grab a Gator/Power/Lucoz-ade and slam it down while you exercise. According to the advertising rhetoric of the past decade or so, these drinks will turn you into strapping, hyper-efficient athletes, often capable of shooting lighting from body parts or causing cameras to spontaneously turn into gritty, slow-motion black and white.
Are these drinks really Scientifically Proven* to Increase Performance* and Make You A Hero*? More specifically: are there any drinks capable of hydrating an active person more effectively than water, and under what circumstances? As I sat in a motorway-spanning rest stop on the coach trip back from York, sipping a lemon sport drink, a friend posed that question to me. I’ve only taken basic biology, but I’m more familiar with chemistry and solutes (and sport!) and couldn’t come up with a convincing answer either way. I agreed to investigate and report back.
As with many scientific questions, the short answer is “it’s complicated.” We absorb water from the food and drink we consume, along with the continuous bodily secretions we make: think saliva and digestive juices in the stomach. We lose water from the obvious excretions, along with moisture from our lungs during breathing, and, most importantly here, sweating.
A bit of basic biology: the body controls many of these water-related processes by manipulating the concentration of dissolved chemicals (solutes) in different locations. These solutes include salts and proteins. Water will tend to move of its own accord towards areas where these solutes are more concentrated. If a cell hoards sodium ions, for example, water will tend to ‘migrate’ into the cell from outside. The movement of water across a membrane, towards areas where solutes are more concentrated, is known as osmosis.
Osmosis will move more water when the difference in solute concentration across a membrane, such as the wall of an intestinal cell, is highest. Drinking water to rehydrate, therefore, makes sense: it contains very low solute concentrations, so the water will move across into the body efficiently.
The counter-argument, in favour of sports drinks, is that they contain electrolytes, such as salts and sugars. The body’s cells can actively accumulate these, which can help them to draw in more water. However, everything we drink passes through our stomach on the way to the intestine before it’s absorbed into the body. As a result, even a glass of pure water will pick up solutes before it gets to the intestine, depending on what we’ve been eating beforehand.
Right. So we know the basic arguments. Take a quick break, have a glass of water, enjoy the photo and then let’s run through what science has to say!
Studying hydration is tricky. It depends on lots of variables: how the fluid is obtained (is it consumed in one big hit, or continuously, or something else), what the fluid contains (salt, sugar, protein), what kind of exercise is performed and for how long, what the time frame is and how dehydration is measured (loss of body mass, fluid balance etc).
In all of the studies I could find, the best thing that could be said about drinking water with additives was that they were useful in recovery from longer exercise sessions. For example, chocolate milk was more effective than a standard sport drink composition or pure water when used in a recovery period between sessions, as measured by endurance. However, that doesn’t tell us whether the body was hydrated better, or simply gained other benefits from the protein, sugar and salt in the milk.
Similar studies show improvements in water retention during and after lengthy exercise using sports drinks over water. This is usually attributed to the replenishment of salts lost in sweat. If we exercise and sweat a lot, we not only lose water, but salts, and our ability to internally regulate hydration may be compromised. I can personally remember a 3-hour basketball session in sweltering Queensland summer heat, when I drank 5 litres of water over the course of the afternoon and ended up feeling absolutely awful – perhaps I’d have benefited from a bit of sugar and salt to keep me topped up!
However, most exercise doesn’t to stretch to an hour or more of intense punishment, where any sports drink benefits will be most obvious. Also, simply eating a snack can help to replenish salts and sugars if necessary.
One aspect of sports drinks that does need to be mentioned is the psychological effect. Water is less palatable than a sweetened drink, and most people find it easier to drink more of a sports drink than water. When we exercise, we tend to view all beverages are more palatable, but sports drinks taste sweeter and less salty as exercise goes on, and sweeter drinks are ‘liked’ more.
For the everyday user, this is the biggest benefit of sports drinks: we are likely to drink more of them during exercise, staying hydrated based on quantity consumed, not quality. For the majority of people, though, water is cheaper, about as effective and doesn’t produce the plastic waste!